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HomeMy WebLinkAboutAgenda - 06-05-2001-9eORANGE COUNTY BOARD OF COMMISSIONERS ACTION AGENDA ITEM ABSTRACT Meeting Date: June 5, 2001 Action Agenda Item No. ~ " ~ .SUBJECT: Whiffed and Northem Center HVAC Options Report and Authorization to Solicit RFP for Desi n Services DEPARTMENT: Public Works PUBLIC HEARING: (Y/N) No ATTACHMENT(S): ^ Staff Summary of Robson &Woese HVAC System Life Cycle Analysis - R,E. Whiffed ~ Northem Centers ^ Introduction to HVAC systems and life cycle analysis and appendices ^ HVAC System Life Cycle Analysis Report: R. E. Whiffed and Northem Centers -Executive Summary INFORMATION CONTACT: Wilbert McAdoo, ext 2625 TELEPHONE NUMBERS: Hillsborough 732-8181 Chapel Hill 9684501 Durham 688-7331 Mebane 33fi-227-2031 PURPOSE: 1) To provide background information regarding heating/ventilation and air conditioning (HVAC) system design considerations and life cycle analysis; and 2) To present Robson 8~ Woese, Inc. life cycle analysis report for Richard E. Whiffed Human Services Center (REWHS) and Northem Human Services Center (NHSC); and 3) To request BOCC approval to issue Request for Proposal documents for HVAC system design work for replacement systems for REWHS and NHSC. BACKGROUND: On June 29, 2000, the BOCC awarded the proposal and approved contracting with Robson and Woese, Inc., Consulting Engineers to prepare a feasibility study that would identify the most economically efficient options for HVAC systems at both the Whiffed Human Services Center and the Northem Human Services Center. Since that time, the Public Works staff has worked with Robson and Woese on completion of the feasibility study. The feasibility study was originally to be completed by Fall 2000, however, one of the principal engineers involved in the project left during this period and the work was delayed significantly. The feasibility study has now been completed and has been attached to this abstract. Also attached to this abstract is a staff summary of the Robson and Woese report, including recommendations. No contract has been executed with Robson and Woese to complete the design of the systems at the Whiffed and Northem Human Services Centers. Based upon the staffing changes and time delays in producing the work, the staff recommends that a new RFP be issued for HVAC system design work for these two facilities. FINANCIAL IMPACT: Funds to carry out the design ofi the HVAC systems are included in the current Capital Investment Plan. A contract citing specific amounts will be presented at such time the RFP process is completed. RECOMMENDATION(S): The Manager recommends that the Board: 1. Receive the attached reports for information; and 2. Identify the strategy of providing HVAC that the Board prefers; and 3. Authorize the solicitation of a Request fior Proposal for design services of HVAC systems at the Whiffed Human Services Center and the Northern Human Services Center pursuant to the preferred strategy. Staff Summary of Robson and Woese HVAC System Life Cycie Analysis Richard E. Whiffed and Northern Human Services Center The Need ^ Existing HVAC systems: o Do not meet modern standards for air quality; o Are at or beyond their useful life; o Have increasingly high maintenance costs; o Are not energy efficient. The Approach ^ In June 2000, the BOCC approved a feasibility study to determine the most economically efficient HVAC system based on life cycle costs for the Richard E. Whiffed and Northern Human Services Center. The following criteria were used to identify and evaluate a range of potential systems for consideration: 1. energy cost; 2. ease of maintenance; 3, controllability; 4. initial cost. Robson and Woese initially considered a wide range of HVAC systems, including: • Fan .Coil/Unit Ventilator with Air-cooled Chiller and Hot Water Bailer • Multi-zone with Air-cooled Chiller and Hot Water Boiler • Packaged or Split Direct Expansion (DX) • ,Packaged Rooftop Type-Multi-zone (PRTU-MZ) • Packaged Rooftop Type- Variable Air Volume (PRTU-VAV) • Solar • Thermal Storage • Through-the-wall Type Packaged Terminal Air Conditioning (PTAC) Units • Water Source Heat Pumps with Evaporative Cooler and Hot Water Boiler • Variable Air Volume (VAV) with Air-cooled Chiller and Hot Water Boiler • Window Air Conditioning System (units) with Steam Boiler and Finned Radiation Heating Findings A short list of system fvr further consideration was developed for each location. A detailed analysis of each of these systems was performed. The following tables summarize the findings of this analysis: Staff Summary of Robson and Woese HVAC System Life Cycle Analysis a Richard E. Whiffed and Northern Human Services Center Richard E. Whiffed Human Services Center System.. Probable Energy' Simple Uniform " Median Description Construction Costs Payback, Annual Cost Useful Cost. ($) r; , a ~$)~Ye y ears ~$) System Life ears Multi-zone, Air- cooled chiller and natural gas $1,204,900 $60,900 N/A $105,800 20 bolter VAV, Air-cooled ~ _ ~ ". "c liiller arld . ;r ~ ` ~ . ~ ~ .; ~ ~~ ~ ~ ~ ~~ natural .gas : ~ ~ ~ ~~ ,~~$1 X3(19,2©0- a»~' ,$49,500 ~~~~ ,~8 0 ~_ ~~~ , ...$98,200 ;. ,~6. ~ 20 p~ler : -, b ._ We recommend the insfallation of a variable air volume system with terminal reheat for the Whiffed Building based on uniform annual cost. Cooling source will be an air cooled wafer chiller to replace the existing water-cooled unit. Northern Human Services Center ~~y~stem Descriih!tian Prnb"able , ":'" fi ' rgy tltiifbrm Median. Constructuon Costs. ($) Annual Cast Useful . Cost ($) y., . ($) SYstem'l_ife f ~ ~~ cars Multi-zone, Air- cooled "Chiller and Fuel Oil Boiler $621,700 $37 100 $60,200 20 Multi-zone, Air- cooled Chiller and Pro ane Boiler $613,200 $58,500 $81 300 20 VA ~ ir-coaled ::f ~.~ ~ r"" i ~~~~ ,~ ~ ~ ~ I , y : ~ . ,' ',4 ~ , Chiller°and Fuel Dil - ~: w ~..., VAV, Air-cooled Chiller and Propane Boiler $595,400 $34,800 $57,000 20 PRTU--Multi-zone $521,300 $57,200 $85,300 15 PRTU-VAV $506,200 $33 200 $60,400 15 PTAC $328,140 $26,800 $69,200 ~ 6 Window AC & 6 (window AC) Steam Boiler $464,660 $24 200 $57,700 20 boiler We recommend the installation of a new HVAC system genera!!y consisting "'of a variable air volume HVAC system with terminal reheat, utilising an air cooled chiller and oil fired boiler based on uniform annua! cost. 5 Introduction In June, 2000, Orange County contracted with Robson and Woese, Inc., Consulting Engineers to perForm a feasibility study to compare potential heating, ventilation and air conditioning (HVAC) systems that could be considered for installation at the Richard E. Whiffed Human Services Center and the Northem Human Services Center. The study was intended to allow the County to select systems that are energy efficient and economical (on a life cycle basis) for both buildings. These new systems would replace existing equipment at both locations. The suitability and feasibility of each potential replacement system was considered for each location. A short list of potential systems was identified and a life cycle cost analysis was prepared for each of the short listed systems. A summary of the evaluations and life cycle analyses has been attached. This summary report is intended to provide additional background information about the Richard E. Whiffed and Northem Human Services Centers, as well as some introductory information and considerations about HVAC system design and operation and maintenance. Aside from the initial construction of a building, replacement of the HVAC system is typically one of the most costly undertakings during the useful life of a building. Background Northern Human Services Center The Northern Human Services Center is located at 5800 Highway 86 North, Hillsborough in the community of Cedar Grove. The building, constructed in 1951, with a 1957 addition housing the kitchen and cafeteria, originally served as an elementary school. It was acquired by Orange County in 1977. The total building size is approximately 27,600 square feet. Construction of the building is concrete block with a brick veneer. Very few modifications have been made to the building since its original construction. Heating is currently provide by means of an oil-fired, steam boiler located in a separate mechanical room. Steam is produced by the 5 Prepared: 05/03/2001 C:\My DocumentsWbstracts2001\06-05-01~-IVACIntroAtt0605.doc Printed: 05/31/2001 6 boiler and distributed through fin-type radiators located in each classroom. A separate, modem cooling package system was installed in the kitchen/dining area in 1999. Windows are original to the building and are metal framed with single-glazed glass panels, with a very low R-value, and therefore are a source of significant energy loss. To allow greater energy efficiency in heating and cooling the building, window replacement is recommended. The type of frame used for the window unit will also significantly affect performance. In general, wood or vinyl frames are thermally superior to metal. In fact, metal framing has such a negative impact on overall window pertormance, that there is usually little benefit to incorporating other strategies, such as low-E films, low-conductivity spacers, etc., unless the frame resistance is first improved. Richard E. Whiffed Human Services Center The Richard E. Whiffed Human Services Center is located at 300 West Tryon Street in Hillsborough. The Center, which previously served as a high school consists of three main buildings. The main building, which currently houses the Library, Department on Aging, some Department of Social Services offices and Department of Housing and Community Development was constructed in 1922. The east wing, which houses the Health Department and DSS offices, was added in 1936 and is joined with the main building through a connecting corl7dor. The Recreation Department is located in a detached building that includes main floor offices, recreation rooms and a .gymnasium in the entire second floor. This building was constructed in 1951,. This property (including the recently deconstructed former Orange Industries building and a parking lot located on the south side of Tryon Street) were acquired by the County in 1975. Renovations to accommodate County functions were completed in 1982. Much of the HVAC equipment dates to the 1970s and 1980s. Major boiler repairs .were completed in 1992 and. the cooling tower was replaced in 1994. Much of the equipment is approaching or past the end of its expected useful life and as such is becoming increasingly unreliable, with increased maintenance costs. Windows were replaced with double glazed, operable windows as part of the County's renovations. htt :% www.ener sernews.com/eunlcda/article information/fundamentals item/0 2637 15033 OO.html 6 Prepared: 05/03/2001 C:\Mv Documents\Abstracts20D1\06-D5-01\HVACIntroAtt0605.doc ~ Printed: 05/31/2001 A redesigned replacement HVAC system has ~ been recommended due to the compartmentalization of former classrooms into much smaller offices and the addition of numerous pieces of heat-generating equipment (computers and peripherals, copiers, etc.). The existing HVAC system design did not anticipate supplying conditioned air to these many small rooms. In addition, HVAC system design in the late 1970's/early 1980s typically attempted to seal the building envelope to the greatest extent possible in order to maximize energy efficiency. Modem designs follow American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) standards for intake of outside air to provide sufficient ventilation for building occupants. HVAC Systems Overview The following section presents a summary of key points concerning HVAC system design and operation that may assist the reader while evaluating the attached report from Robson and Woese. Heating/ventilation/air-conditioning (HVAC) systems circulate and exhaust conditioned air at a prescribed rate of exchange and are crucial to the safety and comfort of a facility. HVAC systems depend on a network of equipment and roams to function properly: All system components must be carefully ,planned and integrated in an effective HVAC system. In designing a system that works, the first consideration always should be the safety, health, and comfort of building occupants. The second concern should be a high standard of efficiency. In building a new HVAC system, much can be learned from whatever system is already in place. Planners should think about what works and what doesn't work in the old HVAC system. Adaptability is also crucial, as whatever system is implemented may have to function safely for thirty years or more. Decision makers should evaluate each individual piece of equipment for a new facility in terms of value and cost, always keeping in mind how all the pieces will work together. 2 The HVAC system includes all heating, -cooling, and ventilation equipment serving a building: furnaces or boilers, chillers, cooling towers, air handling units, exhaust fans, ductwork, filters, steam (or heating water) piping. A properly designed and functioning HVAC system: © provides thermal comfort ^ provides outdoor air to meet the ventilation needs of all occupants o isolates and removes odors and contaminants Thermal Comfort A number of variables interact to determine whether people are comfortable with the temperature of the indoor air. The activity level, age, and physiology of each person affect the thermal comfort requirements of that individual. The American Society of Heating, Refrigerating, and Air- Conditioning Engineers (ASHRAE) Standard 55-1981 describes the temperature and humidity z http://www,pkal.ora/facility,/spaces/hvac.html, "i=ocusing on Facilities." 7 Prepared: 05/03/2001 C:~My oocumentswbstracts2ool~os-o5-alwvAClntroAttoso5.doc Printed: 05/31/2001 8 ranges that are comfortable for most people engaged in largely sedentary activities. The ASHRAE standard assumes "normal" indoor clothing. Uniformity of temperature is important to comfort. When the heating and cooling needs of a room within a single zone change at different rates, rooms that are served by a single therrnostat may be at different temperatures. Humidity is a factor in thermal comfort. Raising relative humidity reduces the ability to lose heat through perspiration and evaporation, so that the effect is similar to raising the temperature. Humidity extremes can also create other IAQ problems. Excessively . high or low relative humidities cam produce discomfort, while high relative humidities can promote the growth of mold and mildew. Ventilation fo Meef Occupant Needs Most air handling units distribute a blend of outdoor air and recirculated indoor air. HVAC- designs may also include units that introduce 100% outdoor air or that simply transfer air within the building. Thermal comfort and ventilation needs are met by supplying "conditioned" air (a blend of outdoor and recirculated air that has been filtered, heated or cooled, and sometimes humidified or dehumidified). The amount of outdoor air considered adequate for proper ventilation has varied substantially over time. Tha current guideline issued by ASHRAE is ASHRAt; Standard 62-1989. (ASHRAE committees are currently discussing and debating a revision to the 62 standard.) The building code that was in force when your buildings HVAC system was designed may well have established a lower amount of ventilation (in cubic feet of outdoor air per minute per person) than is currently recommended. ~ - A copy of the Executive Summary of the Robson and Woese HVAC System Life Cycle Analysis for Whiffed and Northern Buildings follows. The following appendices have also been included to provide additional background information about HVAC system design and selection: o HVAC Systems: How They Work o Choosing the Best HVAC System We will be pleased to provide additional information or details upon request. s htto:Nwww.bagl.com/index.htm 8 Prepared: 05/03/2001 C:\My Documents\Abstracts2001\06-0~01\FiVACIntroAtt0605.doc Printed: 05/31/2001 Fundamental Series Item :HVAC Systems: How They Work Posted on: 11/09r1D00 HVAC Systems: How They Work Samuel C. Monger file:///c~/windows/T~MF/0,2637,14506,0 The main purpose of commercial HVAC (heating, ventilating, and air conditioning) s~ , provide the people working inside buildings with "conditioned" air so that they will hay comfortable and safe work environment. "Conditioned" air means that air is clean an and the temperature, humidity, and movement of the air are within certain comfort ra Many factors affect the way people respond to their work environment. Air quality is ~ factors. The American Society of Heating, Refrigerating and Air-Conditioning frngine (ASHRAE) has established standards which outline air quality for indoor comfort con are acceptable to 80% or more of a commercial building's occupants. Generally, the: comfort conditions, sometimes called the "comfort zone," are between 68 degrees F degrees F for winter and 73 degrees F to 79 degrees F during the summer. Both the temperature ranges are for room air at approximatety 5b°~ relative humidity and mop velocity of 30 feet per minute or slower. Figure 1. HVAC system components. The basics of heating, ventilating, and air conditioning systems undamental Series Item :HVAC Systems: How They Work 1`ile:///c~/windows/T'EMP/0,2637,14506,OO.h ld Posted on: 11/09/2000 HVAC Systems: How They Work Samuel C. Monger The main purpose of commercial HVAC (heating, ventilating, and air conditioning) s~ provide the people working inside buildings with "conditioned" air sa that they will hay comfortable and safe work environment. "Conditioned" air means that air is clean an and the temperature, humidity, and movement of the air are within certain comfort ra Many factors affect the way people respond to their work environment. Air quality is ~ factors. The American Society of Heating, Refrigerating and Air-Conditioning Engine (ASHRAE) has established standards which outline air quality far indoor comfort con 'are acceptable to 80% or more of a commercial building's occupants. Generally, the: comfort conditions, sometimes called the "comfort zone," are between 68 degrees F degrees F for winter and 73 degrees F to 79 degrees F during the summer. Bath the temperature ranges are for roam air at approximately 5Q% relative humidity and may velocity of 30 feet per minute or slower. The basics of heating, ventilating, and air conditioning systems Fundamental Series Item : HVAC Systems: How They Work file:///c~/windows/TEMP/0,2637, I4506,C x~ Heat and Temperature Meat is energy in the form of molecules in motion. As a material becomes warmer, it motion and energy level (temperature) increases, and vice versa. Temperature desc level of heat (energy) with reference to no heat. Heat is a positive value relative to nc Therefore, warm, hot, cool and cold are comparative terms used to describe higher c temperature levels. The Fahrenheit scale is the standard system of temperature measurement used in tl States. The U.S. is one of the few countries in the world that still uses this system. N countries use the metric temperature measurement system-the Celsius scale. Howe Fahrenheit and Celsius scales are currently used interohangeably ih the U.5. to desc equipment and fundamentals in the heating, ventilating and air conditioning industry. Heat Transfer Heat naturally flows from a higher energy level to a lowar energy level. In other word: travels from a warmer material to a cooler material. The unit of measurement used t~ the quantity of heat contained in a material is a British thermal unit (Btu). When there is a temperature difference between two materials, heat transfer will oa temperature difference is the driving force behind heat transfer, i. e., the greater the temperature difference, the greater the heat transfer. The rate o transfer can be described by adding the dimension of time, far example, British them hour (Btu/hr or Btuh). Types of Heat Transfer The three types of heat transfer are conduction, radiation, and convection. Your hang cold wall is an example of heat transfer by conduction. A portable electric heater that red-hot is an example of heat transfer by radiation. Heat transfer by convection is when some material that is readily movable such as a steam, and refrigerant moves heat from one location to another. For example, when heated, it rises; this is heat transfer by "natural" convection. "Forced" convection is v- or pump is used to convey heat in fluids such as air and water. Compare the words " (the action of conveying) and "convey" (to take or carry from one place to another). undamental Series Item :'HVAC Systems: How They Work file:///c~/windows/TEMP/0,2637,1 ~506,OO.h is Heat and Temperature Heat is energy in the form of molecules in motion. As a material becomes warmer, it motion and energy level (temperature) increases, and vice versa. Temp~:rature desc level of heat (energy) with refierence to no heat. Heat is a positive value relative to nc Therefore; warm, hat, cool and cold are comparative terms used to describe higher c temperature levels. The Fahrenheit scale is the standard system of temperature measurement used in tl States. The U.S. is one of the few countries in the world that still. uses this system. N countries use the metric temperature measurement system-the Celsius scale. Howe Fahrenheit and Celsius scales are currently used interchangeably in the U.S. to desc equipment and fundamentals in the heating, ventilating and air conditioning industry. Heat Transfer Heat naturally flows from a higher energy level to a lower energy level. In other word: travels from a warmer material to a cooler material. The unit of measurement used t~ the quantity of heat contained in a material is a British thermal unit (Btu). When there is a temperature difference between two materials, heat transfer will oce temperature difference is the driving force behind heat transfer, i. e., the greater the temperature difference, the greater the heat transfer. The rate o transfer can be described by adding the dimension of time, far example, British them hour (Btu/hr or Btuh). Types of Heat Transfer The three types of heat transfer are conduction, radiation, and convection. Yeur hang cold wall is an example of heat transfer by conduction. A portable electric heater than red-hot is an example of heat transfer by radiation. Heat transfer by convection is when some material that is readily movable such as a steam, and refrigerant moves heat from one location to another. For example, when heated, it rises; this is heat transfer by "natural" convection. "Forced" convection is ~ or pump is used to convey heat in fluids such as air and water. Compare the words " (the action of conveying) and "convey" (to take or carry from one place to another). Fundamental Series Item :HVAC Systems: How They Work file:/!/c ~/windows/TEMP/0,2637,14506,( 13 HVAC System ,Components The basic components in a common central HVAC system as illustrated in Figure 1 1: Fan(s) to circulate the supply air (5A) and return air (RA). 2. Supply air ductwork in which the air flows from the supply fan to the conditioned sl 3. Air devices such as supply air outlets and return air inlets. 4. Return air path or ductwork in which the air flows back from the conditioned spacE mixed air chamber (plenum). 5. Outside air (OA) device such as an opening, louver or duct to allow for the entrant outside air into the mixed air chamber. 6. Mixed air chamber to receive the return air and mix it with outside air. 7. Filter section(s) to remove dirt and dust particles from the mixed air. 8. Heat exchanger(s) such as hot water coil(s), steam coil(s), refrigerant evaporator( chilled water coil(s) to add heat to or remove heat from the circulated air. 9. Auxiliary heating devices such as natural gas furnace(s) or electric heating elemer 10. Compressor(s) to compress the refrigerant vapor and pump the refrigerant arour system. . 11. Condenser(s) to remove heat from the refrigerant vapor and condense it to a liq~ 12. Fan(s) to circulate outside air across air-cooled condenser(s) 13. Pump(s) to circulate water through water-cooled condenser(s); condenser water (CWP); and condenser water supply (CWS) and return (CWR). 14. Pump(s) to circulate hot water from the boiler(s) through the hot water coil(s) ant circulate chilled water from the chillers) through the chilled water coil(s) and back to chiller(s). 15. For central systems, water or steam boiler(s) as a central heating source. 16. For central systems, water chillers) as a central cooling source. 17. For central systems, cooling tower(s) with water~ooled condenser(s). 18. Controls to start, stop, or regulate the flow of air, water, steam, refrigerant and el HVAC System Example Airflow: The volume of air required to heat, cool and provide good indoor air quality is based on the heating, cooling and ventilation loads. The air volumes are in units of c per minute (cfm). Constant volume fans (supply and return) ciroulate the conditioned For the example system (Figure 1), the total volume of air supplied to the conditioner 6,000 cfm. Of this 6,000 cfm circulated through the conditioned space and back to tl' handling unit (AHU), 1,000 cfm is exhausted in the return air plenum through.the exf -(EA) damper. The remaining 5,000 cfm goes into the mixed air chamber. At the same time, 1,000 cfm is exhausted another 1,000 cfm is brought in through to air (OA) dampers in the mixed air plenum. This 1,000 cfm of outside air mixes with tl remaining 5,000 cfm of return air. The 6,000 cfm of mixed air then travels through th the coil sections. indamental Series Item :HVAC Systems: How They Work file:///cl/windows/TEMP/0,2637,14506,OO.h~ 14 HVAC System Components The basic components in a common central HVAC system as illustrated in Figure 1 ; 1. Fan(s) to circulate the supply air (SA) and retum air (RA). 2. Supply air ductwork in which the air flows from the supply fan to the conditioned sl 3. Air devices such as supply air outlets and return air inlets. 4. Retum air path or ductwork in which the air flaws back from the conditioned space mixed air chamber (plenum).. 5. Outside air (OA) device such as an opening, louver or duct to allow for the entranr outside air into the mixed air chamber. 6. Mixed air chamber to receive the return air and mix it with outside air. 7. Filter section(s) to remove dirt and dust particles from the mixed air. 8. Heat exchanger(s) such as hot water coil(s), steam coil(s), refrigerant evaporator( chilled water coil(s) to add heat to or remove heat from the circulated air. 9. Auxiliary heating devices such as natural gas furnace(s) or electric heating elemei 10. Compressor(s) to compress the refrigerant vapor and pump the refrigerant arour system. 11. Condenser(s) to remove heat from the refrigerant vapor and condense it to a liq~ 12. 1=an(s) to circulate outside air across air-cooled condenser(s) 13. Pump(s) to circulate water throughwater-cooled condenser(s); condenser water (CWP); and condenser water supply (CWS) and retum (CWR). 14. Pump(s) to circulate hot water from the boiler(s) through the hot water coil(s) anc circulate chilled water from the chillers) through the chilled water coil(s) and back to chiller(s). 15. For central systems, water or steam boiler(s) as a central heating source. 16. For central systems, water chillers) as a central cooling source. 1 T. For central systems, cooling tower(s) with water-cooled condenser(s). 18. Contrels to start, stop, or regulate the flow of air, water, steam, refrigerant and el HVAC System Example AirFlow: The volume of air required to heat, cool and provide good indoor air quality i; based on the hea#ing, cooling and ventilation loads. The air volumes are in units of c per minute (cfm). Constant volume fans (supply and retum) circulate the conditioned For the example system (Figure 1), the total volume of air Supplied to the conditioner 6,000 cfm. Of this 6,000 cfm circulated through the conditioned space and back to tf• handling unit (AHU), 1,000 cfm is exhausted in the retum air plenum. through the exf -(F.A) damper. The remaining 5,000 cfm goes into the mixed air chamber. At the same time, 1,000 cfm is exhausted another 1,000 cfm is brought in through th air (DA) dampers in the mixed air plenum. This 1,000 cfm of outside air mixes with tl remaining 5,000 cfm of return air. The 6,000 cfm of mixed air then travels through th the coil sections. Fundamental Series Item :HVAC Systems: How They Work file:///c~/windows/TEMP/0,2637,14506.0 15 Heating: The heating load requirement is based on design indoor and outdoor winter The design conditioned space heating load is 227,000 Btu/hr. This is the amount of I (mainly by conduction) through the walls, windows, doors, roofs, etc., in the winter. P amount of heat is required to heat the outside ventilation air based on design conditi~ To maintain the temperature and humidity in the comfort zone far the conditioned sp heating cycle is this: The supply air leaves the heating coil carrying 227,000 Btuh of I air goes through the supply air fan (SAF), down the insulated supply duct, past the rr volume dampers (MVD) which have been set for the correct amount of air for each c into the conditioned space. The supply air gives up all of its 227,000 Btuh of heat to I conditioned space to replace the.227,000 Btuh that is leaving the space through the etc. As the air gives up its heat it makes its way through the room and into the return inlets, then into the return air duct and back to the air handling unit. This AHU is loco roof and is therefore designated as a "roof top unit" (RTU). The return air goes through the return air fan (RAF), through the return air automatic temperature- controlled (ATC) dampers into the mixed air chamber and mixes with tl air (OA). The mixed air flows through the filters, through the cooling coil (which is off the heating coil. The mixed air travels through the heating coil where it picks up heat conduction through the hot water tubes in the coil. In addition to the tubes, the heater has fins attached to the tubes to facilitate the heat transfer. The supply air leaves the coil carrying its 227,000 Btuh of heat and the air cycle repeats. The water, after giving up heat to the air, leaves the coil and goes back to the oil-fire through the hot water return (HWR) pipe and into the boiler where it picks up the sar of heat that it has just given up in the coil. The water leaves the boiler, flows through water pump (HWP) and is pumped through the hat water supply (HWS) or heating h supply (HHWS) piping into the heating coil to give up its heat into the mixed air and t cycle repeats. Ventilating: In the human respiratory process, oxygen is inhaled and carbon dioxide, contaminant, is exhaled. In commercial buildings, carbon dioxide and other contamir as cigarette smoke must be continuously removed or uncomfortable or unhealthy co result. "Ventilation" is the process of supplying outside air to buildings in the proper s offset the contaminants and odors produced by people and equipment. In many situations, local building codes stipulate the amount of ventilation required ft commercial buildings and work environments to maintain good indoor air quality (IAC requirement is usually 20 cubic feet per minute of outside air for each occupant. The HVAC system supplies air to a suite in an office complex designed for 50 people. Th outside air requirement is 1,000 cfm. Air Conditioning (Cooling): For this system, the total heat given off by the people, IigF equipment in the conditioned space plus the heat entering the space through the out windows, doors, roof, etc., and the heat contained in the outside ventilation air will be approximately 195,000 Btu/hr. A ton of refrigeration is equivalent to 12,000 Btu/hr of Therefore, this HVAC system requires a chiller that can provide 16.25 tons of coolinc To maintain the proper temperature and humidity in the conditioned space, the coolie described as: The supply air (which is approximately 20 degrees (F cooler than the conditioned space) leaves the cooling coil and goes through heating coil (which is of the supply air fan, down the duct and into the conditioned space. The cool supply air heat in the conditioned space. The warmed air makes its way into the return air inlet; the return air duct and back to the air handling unit. The return air goes through the r into the mixed air chamber and mixes with the outside air. The mixed air goes throu4 and into the cooling coil. The mixed air flows through the cooling coil where it gives ~ into the chilled water tubes in the coil. This coil also has fins attached to the tubes to heat transfer. The cooled supply air leaves the cooling coil and the air cycle repeats. The water, after picking up heat from the mixed air, leaves the cooling coil and goes chilled water return (CHWR) pipe to the water chillers evaporator. The "warmed" wa into the chiller's evaporator (sometimes called the water cooler) where it gives up the undamental Series ltem :HVAC Systems: How They Work file)//cl/windows/TEMP/0,2637,1 ~}506,OO.h~ 16 Heating: The heating load requirement is based on design indoor and outdoor winter The design conditioned space heating load is 227,000 Btu/hr. This is the amount of I (mainly by conduction) through the walls; windows, doors, roofs, etc., in the winter. P amount of heat is required to heat the outside ventilation air based on design conditi~ To maintain the temperature and humidity in the comfort zone for the conditioned sp heating cycle is this: The supply air leaves the heating coil carrying 227,000 Btuh of I air goes through the supply air fan (SAF), down the insulated supply duct, past the rr volume dampers (MVD) which have been set for the correct amount of air for each c into the conditioned space. The supply air gives up all of its 227,000 Btuh of heat to i conditioned space to replace the 227,000 Btuh that is leaving the space through the etc. As the air gives up its heat it makes its way through the room and into the return inlets, then into the return air duct and back to the air handling unit. This AHU is loco roof and is therefore designated as a "roof top unit" (RTU). The return air goes through the return air fan (RAF), through the return air automatic temperature- controlled (ATC) dampers into the mixed air chamber and mixes with tl air (OA). The mixed air flows through the filters, through the cooling coil (which is off the heating coil. The mixed air travels through the heating coil where it picks up heat conduction through the hot water tubes in the coil. In addition to the tubes, the heater has fins attached to the tubes to facilitate the heat transfer. The supply air leaves the coil carrying its 227,000 Btuh of heat and the air cycle repeats. The water, after giving up heat to the air, leaves the coil and goes back to the oil-flre~ through the hot water. return (HWR) pipe and into the boiler where it picks up the sar of heat that it has just given up in the coil. The water leaves the boiler, flows through water pump (HWP) and is pumped through the hot water supply (HWS) or heating h supply (HHWS) piping into the heating coil to give up its heat into the mixed air and t cycle repeats. Ventilating: In the human respiratory process, oxygen is inhaled and carbon dioxide, contaminant, is exhaled. In commercial buildings, carbon dioxide and other contamir as cigarette smoke must be continuously removed or uncomfortable or unhealthy co result. "Ventilation'" is the process of supplying outside air to buildings in the proper G offset the contaminants and odors produced by people and equipment. In many situations, local building codes stipulate the amount of ventilation required fc commercial buildings and work environments to maintain good indoor air quality (IAC requirement is usually.20 cubic feet per minute of outside air for each occupant: The HVAC system supplies air to a suite in an office complex designed for 50 people. Th outside air requirement is 1,000 cfm. Air Conditioning (Cooling): For this system, the total heat given off by the people, ligt equipment in the conditioned space plus the heat entering the space through the out windows, doors, roof, etc., and the heat contained in the outside ventilation air will be approximately 195,000 Btu/hr. A ton of refrigeration is equivalent to 12,000 Btu/hr of Therefore, this HVAC system requires a chiller that can provide 16.25 tons of coolinf To maintain the proper temperature and humidity in the conditioned space, the coolie described as: The supply air (which is approximately 20 degrees (F cooler than the r conditioned space) leaves the cooling coil and goes through heating coil (which is of the supply air fan, down the duct and into the conditioned space. The coal supply air heat in the conditioned space. The warmed air makes its way into the return air inlet: the return air duct and back to the air handling unit. The return air goes through the r into the mixed air chamber and mixes with the outside air. The mixed air goes throuc and into the coaling coil. The mixed air flows through the cooling coil where it gives ~ into the chilled water tubes in the tail. This coil also has fins attached to the tubes to heat transfer. The cooled supply air leaves the cooling coil and the air cycle repeats. The water, after picking up heat from the mixed air, leaves the cooling coil and goes chilled water return (CHWR) pipe to the water chiller's evaporator. The "warmed" wa into the chillers evaporator (sometimes called the water cooler) where it gives up the Fundamental Series ltem :HVAC Systems: How They Work file)//cVwindows/TEMP/0,2637,14506,0 17 the mixed air) into the refrigeration system. The newly "chilled" water leaves the eval goes through the chilled water pump (CHWP) and is pumped through the chilled wa1 (CHWS) piping into the cooling coil to pick up heat from the mixed air and the water repeats. The evaparatar is a heat exchanger that allows heat from the CHWR to flow by cons the refrigerant tubes. The liquid refrigerant in the tubes "boils off' to a vapor removin the water and conveying the heat to the compressor and then to the condenser. The the condenser is conveyed to the cooling tower by the condenser water. Finally, outs drawn across the cooling tower, removing the heat from the water through the prose evaporation. An HVAC system is simply a group of components working together to move heat to wanted (the conditioned space) or to remove heat from where it is not wanted (the c~ space) and put it where it is unobjectionable (the outside air). Samuel C. Manger, CEM, CDSM, is the principal of the energy systems training firm, Monger Worldwide Consulting. The author of numerous articles and books on perforr testing and evaluation of HVAC/R systems, Monger is a nationally recognized energy systems educator and enerav enaineerina orofessional_ Copyright ©2000 by Business News Publishin Co. .tndamen~l Series Item :HVAC Systems: How'1'hey Work file:///cl/windows/TEMP/0,2637,14506,OO.h1 1S the mixed air) into the refrigeration system. The newly "chilled" water leaves the eval goes through the chilled water pump (CHWP) and is pumped through the chilled wa1 (CHWS) piping into the cooling coil to pick up heat from the mixed air and the water repeats. The evaporator is ~ heat exchanger that allows heat from the CHWR to flaw by cone the refrigerant tubes: The liquid refrigerant in the tubes "boils off' to a vapor rempvin the water and conveying the heat to the compressor and then to the condenser. The the condenser is conveyed to the coaling tower by the condenser water. Finally, outs drawn across the cooling tower, removing the heat from the water through the prose evaporation. An HVAC system is simply a group of components working together to move heat to wanted (the conditioned space) or to remove heat from where it is not wanted (the c~ space) and put it where it is unobjectionable (the outside air). Samuel C. Monger, CAM, CDSM, is the' principal of the energy systems training firm, Monger Worldwide Consulting. The author of numerous articles and books on perforr testing and evaluation of HVAC/R systems, Manger is a nationally recognized energy systems educator and energy engineering professional: Copyright O 2000 by Business News Publishin Co. Fundamental Series Item.: Choosing the Best HVAC System file:///cl/windows/1`EMP/0,2637,162$7,( 19 Posted on:'12/08r2000 Choosing the Best HVAC System By Samuel C. Monger Which is suited to your application: unitary, rooftop, or packaged? The purpose of an HVAC (heating, ventilating, and air-conditioning) system is to prop maintain environmental conditions within an area called the "conditioned space." The system selected is determined by the mechanical designer's knowledge of systems building owner's financial and functional goals. The commercial system selected for a particular application should endeavor to prop optimum environment for employee comfort and productivity, process function, and c air quality with energy efficiency and cost-savings. Different systems will satisfy each objectives with different degrees of success. It is up to the designer and the owner tc correct assessments. In most applications, there are several choices for the type of system to use: The sel the type of HVAC system by the designer and the building owner is a critical decision designers responsibility to consider the various systems and select the one that will best combination of initial cost, operating cost, performance, and reliability based on .understanding of the owner's needs and goals. In the selection process all factors m analyzed, but cost of installation and operation are usually foremost. Some of the many cost concerns include initial or installation cost, operating and ma cost, and equipment replacement costs. Another cost concern that may be overlook designer is the cost associated with equipment failure. For example, how often migh system or component be expected to fail and what is the cost in loss of product and How long will the system be down? Wow will the comfort, safety and productivity of tl' occupants be affected by such a failure and what are these costs? Depending on the owner's goals, each of these concerns has a different priority. Mo: do not have knowledge or understanding of the advantages and disadvantages of th types of systems, so it is up to the designer to advise the owner which is best for eac application. Likewise, the designer usually does not usually have a complete understanding of al -owners financial and functional goals. For these reasons, the best situation is when and owner are bath involved in the HVAC selection process. undamental Series Item : Choosing the Best HVAC System file:///ci/windowsrfEMP/0,2637,162$7,OO.h 20 Posted on: 12/0$12000 Choosing the Best HVAC System By Samuel C. Monger Which is suited to your application: unitary, rooftop, or packaged? The purpose of an HVAC (heating, ventilating, and air-conditioning) system is to prrn maintain environmental conditions within an area called the "conditioned space." ThE system selected is determined by the mechanical designer's knowledge of systems ; building owners financial and functional goals. The commercial system selected for a particular application should endeavor to prop optimum environment for employee comfort and productivity, process function, and 4 air quality with energy efficiency and cost-savings. Different systems will satisfy each objectives with different degrees of success. It is up to the designer and the owner tc correct assessments. In most applications, there are several choices for the type of system to use. The sel the type of HVAC system by the designer and the building owner is a critical decisior designees responsibility to consider the various systems and select the one that will best combination of initial cast, operating cost, performance, and reliability based on understanding of the owner's needs and goals. In the selection process all factors m analyzed, but cost of installation and operation are usually foremost. Some of the many cost concems include initial or installation cost, operating and ma cost, and equipment replacement costs. Another cost concern that may be overlook designer is the cost associated with equipment failure. For example, how often migh system or component be expected to fail and what is the cost in loss of product and How long will the system be down? How will the comfort, safety and productivity of tr occupants be affected by such a failure and what are these costs? Depending on the owner's goals, each of these concerns has a different priority. Mo: do not have knowledge or understanding of the advantages and disadvantages of th types of systems, so it is up to the designer to advise the owner which is best for eat application. Likewise, the designer usually does not usually have a complete understanding of al owner's financial and functional goals. For these reasons, the best situation is when and owner are, both involved in the HVAC selection process. Fundamental Series Item :Choosing the Best HVAC System file:///c~windows/TEMP/0,2637,162$ 7,C 21 HVAC Selection The first step in the selection process is for the designer to ascertain and document owner the desired environmental conditions for the building or conditioned space. The designer must also learn and document the restrictions placed on the system de example, what is the required equipment space for a particular system versus what i Unfortunately, it is the nature of the business that very few projects allow as much dE evaluation of all conditions and alternatives as some would like. Therefore, the desig also rely on common sense and subjective experience to narrow the choice of systei Step two in the selection process is determining the building's heating and cooling to example, is the cooling load mostly sensible or latent? Is the load relatively high or Ic square foot of conditioned area as compared to other similar buildings? Is the load u distributed throughout the conditioned spaces, and is it relatively constant or does it greatly? How does the load vary with time and operating conditions? Determining the heating and cooling loads establishes the system's capacity requires Cooling loads and humidity requirements are used to size air-conditioning (comfort a cooling) systems. In other systems, heating and/or ventilation may be the critical factors in sizing and s For example, a building may require a large air handling unit and duct system to prop quantities of outside air for ventilation or as makeup air to replace air exhausted fron building. In other buildings, in colder climates for instance, heating may be the deterr factor on equipment size. The physical size of the equipment can be estimated from and cooling load information alone. This information can help to reduce the choice o' those that will fit the space available. There are also choices to be made depending on if the system is to be installed in a building or an existing building. In existing buildings, for example, the HVAC system designed for the loads when the building was built. This means if new systems are tc integrated with existing ones (in order to keep costs down or for other reasons), the i retrofitted systems must be adaptable to existing equipment, ductwork and piping, ai equipment or systems must fit into existing spaces. If new systems are to pertorm pr when tied in with existing systems, the old and the new must be looked at carefully a entirety. The designer will need to determine how a change to one part of a system v another part and a how a change in one system will afFect another system. The number of choices is narrowed further to those systems that will work well on pr given application and size and are compatible with the building architecture. indamental Series Item :Choosing the Best HVAC System HVAC Selection file:///cl/windows/TEMP/0,2637,1 b287,00.h 22 The first step in the selection process is for the designer to ascertain and document owner the desired environmental conditions for the building or conditioned space. The designer must also learn and document the restrictions placed on the system de example, what is the required equipment space for a particular system versus what i Unfortunately, it is the nature of the business that very few projects allow as much de evaluation of all conditions and alternatives as some would like. Therefore, the desig also rely on common sense and subjective experience to narrow the choice of systei Step two in the selection process is determining the building's heating and cooling to example, is the cooling load mostly sensible or latent? Is the load relatively high or Ic square foot of conditioned area as compared to other similar buildings? Is the load u distributed throughout the conditioned spaces, and is it relatively constant or does it greatly? How does the load vary with time and operating conditions? Determining the heating and cooling loads establishes the system's capacity require Cooling loads and humidity requirements are used to size air-conditioning (comfort a cooling) systems. In other systems, heating and/or ventilation may be the critical factors in sizing and s For example, a building may require a large air handling unit and duct system to prop quantities of outside air for ventilation or as makeup air to replace air exhausted fron building. In other buildings, in colder climates for instance, heating may be the deterr factor an equipment size. The physical size of the equipment can be estimated from and cooling load information alone. This information can help to reduce the choice o' those that will fit the space available. There are also choices to be made depending on if the system is to be installed in a building or an existing building. In existing buildings, for example, the HVAC system designed for the loads when the building was built. This means if new systems are tc integrated with existing ones.(in order to keep costs down or for other reasons), the i retrofitted systems must be adaptable to existing equipment, ductwork and piping, ai equipment or systems must fit into existing spaces. If new systems are to pertorm pr when tied in with existing systems, the old and the new must be looked at carefully a entirety. The designer will need to determine how a change to one part of a system v another part and' a how a change in one system will affect another system. The number of choices is narrowed further to those systems that will work well on pr given application and size and are compatible with the building architecture. Fundamental Series Item :Choosing the Best HVAC System file:///cl/windows/TLMP/0,2637,16287,( 2 System Selection Guidelines Each of the following issues should be taken into consideration each time an HVAC selected. • Financial factors • Initial cost • Operating costs Maintenance and repair cost • Equipment replacement or upgrading cost • Equipment failure cost • Return on investment (ROI) • lip Building conditions • New or existing building ar space • Location • Orientation • Architecture • Climate and shading • Configuration • Construction • Codes and standards • Usage • Occupancy • Process equipment • Energy availability • Types • Reliability • Costs • Control scheme • Zone control • Individual control undamental Series Item :Choosing the Best HVAC System file:///c~/windows/TEMP/0,2637,16287,OO.h 24 System Selection Guidelines Each of the fiollowing issues should lie taken into consideration each time an HVAC selected. • Financial factors • Initial cost • Operating casts • Maintenance and repair cost • Equipment replacement or upgrading cost • Equipment failure cast • Return on investment (ROI) • lip Building conditions • New or existing building or space • Location • Orientation • Architecture • Climate and shading • Configuration • Construction • Codes and standards • Usage • Occupancy • Process equipment • Energy availability • Types • Reliability • Costs • Control scheme • Zone control • Individual control Fundamental Series Ttem :Choosing the Best HVAC System file:!//c~/windows/'I'BMP/l),2637,1 d287,f 25 Types Of HVAC Systems There are four basic types of HVAC systems used in commercial buildings. They are and water, all-water, and unitary. Water systems are also called hydronic systems. F the term used for heating and cooling with liquids. All-air-type systems provide heated or cooled air to the conditioned space through a system. The basic types of all-air duct systems are: single-zone, multizone, dual or c terminal reheat, constant air volume, variable air volume (VAV), and combination sy: the typical system, cooling and heating is accomplished by the mixed air (a combina~ return and outside air) passing over a refrigerant coil (cooling) or a heat exchanger The basic air-water system (also called air-hydronic) is a central system similar to the system with chilled water coils instead of refrigerant coils for cooling (with an air-cool condenser) and hot water coils for heating. A variation of this system is the water-air (hydronic-air) system with refrigerant coils for cooling and awater-cooled condenser All-water (all-hydronic) systems accomplish space cooling by circulating chilled Ovate central refrigeration system through cooling coils in air handling units (also called ter or fan-coil units). The units are; located in the building's conditioned spaces. Heating is accomplished by circulating hot water through the same (f~oling/heating) through a separate heating coil. When one coil is used for cooling only, heating only, and cooling at various times, a two-pipe water distribution system is used. When twc used, one for heating and one for cooling, afour-pipe water distribution system is us may also be accomplished using electricity or steam. Straight water heating systems commonly use convectors, baseboard radiation, fin tube radiation, standard fan-coil unit heaters. Unitary Systems A unitary system is an air-conditioning unit that provides all or part of the air-conditioi functions. The components, fan(s), filter(s), controls, and the cooling apparatus (refri refrigerant piping, compressor(s), and condenser) are all factory-assembled into an i package. Components are matched and assembled at the factory to achieve specific pertormance objectives in accordance with industry~stablished increments of t:apac cfm of air per ton of refrigeration). These performance objectives are set by trade as that have developed standards by which manufacturers may test and rate their equip These performance parameters and standards allow for the manufacture of quality factory-tested systems. Types of unitary systems include window-mounted air conditioners and heat pumps, through-the-wall air conditioners and heat pumps, packaged terminal air conditioner pumps, packaged units, and rooftop units. Unitary systems are used in a wide range of applications and may or may not be use central systems. Cooling capacity can range from fractional tonnage for window-type 100 tons of refrigeration or more for packaged. units. A unitary system that uses the i system as the primary heating source is a heat pump. Commercial~rade unitary sys called packaged units. Some packaged units also have heating apparatus (e.g., nat~ heat exchanger, electric elements, steam or hot water coils) and humidifiers. A pack designed to be placed on the roof is called a rooftop unit. Packaged Units Packaged units are used in almost all types of building applications, especially in apl where pertormance requirements are less demanding, and relatively low initial cost simplified installation are important. Applications include hotels, manufacturing plant: facilities, motels, multi-0ccupancy dwellings, nursing homes, office buildings, school: centers, and other buildings with limited life or limited income potential. However, pa~ units are also used in applications where dedicated, high performance levels are req as computer rooms and laboratories. indamental Series Item : Choosing the Best HVAC System filet//cl/windows/TEMP/0,2637,16287,OO.ht Types Of HVAC Systems There are four basic types of HVAC systems used in commercial buildings. They are and water, all-water, and unitary. Watersystems are also called hydronic systems. F the term used for heating and cooling with liquids. All-air-)ype systems provide heated or cooled air to the conditioned space through a system. The basic types of all-air duct systems are: single-zone, multizone, dual or c terminal reheat, .constant air volume, variable air volume (VAV), and combination sy: the typical system, cooling and heating is accomplished by the mixed air (a combina' return and outside air) passing over a refrigerant coil (cooling) or a heat exchanger The basic air-water system (also called air-hydronic) is a central system similar to the system with chilled water coils instead of refrigerant coils for cooling (with an air-cool condenser) and hot water coils for heating. A variation of this system is the water-air (hydronic-air) system with refrigerant coils for cooling and awater-cooled condenser All-water (all-hydronic) systems accomplish space cooling by circulating chilled Ovate central refrigeration system through cooling tails in air handling units (also called ter or fan-coil units). The units are located in the building's conditioned spaces. Heating is accomplished by circulating hot water through the same (cooling/heating) through a separate heating coil. When one coil is used for cooling only, heating only, and cooling at various times, atwo-pipe water distribution system is used. When twc used, one for heating and one forcooling, a four--pipe water distribution system is us may also be accomplished using electricity or steam. Straight water heating system commonly use convectors, baseboard radiation, fin tube radiation, standard fan-coil unit heaters. zs Unitary Systems A unitary system is an air-conditioning unit that provides all or part of the air-conditioi functions. The components, fan(s), filter(s), controls, and the cooling apparatus (refri refrigerant piping, compressor(s), and condenser) are all factory-assembled into an i package. Components, are matched and assembled at the factory to achieve specific performance objectives in accordance with industry-established increments of capac cfm of air per ton of refrigeration). These performance objectives are set by trade as that have developed standards by which manufacturers may test and rate their equiF These performance parameters and standards allow for the manufacture of quality-c factory-tested systems. Types of unitary systems include window-mounted air conditioners and heat pumps, through-the-wall air conditioners and heat pumps, packaged terminal air conditioner pumps, packaged units, and rooftop units. Unitary systems are used in a wide range of applications and may or may not be use central systems. Cooling capacity can range from fractional tonnage for window-type 100 tons of refrigeration or more for packaged units. A unitary system that uses the i system as the primary heating source is a heat pump. Commercial-grade unitary sys called packaged units. Some packaged units also have heating apparatus (e.g., nat~ heat exchanger, electric elements, steam or hot water coils) and humidifiers. A pack designed to be placed on the roof is called a rooftop unit. Packaged Units Packaged units are used in almost all types of building applications, especially in apl where performance requirements are less demanding, and relatively low initial cost simplified installation are important. Applications include hotels, manufacturing planl~ facilities, motels, multi-occupancy dwellings, nursing homes, office buildings, school: centers, and other buildings with limited life or limited income potential. Wowever, pay units are also used in applications where dedicated, high pertormance levels are req as computer rooms and laboratories. Fundamental Series Item :Choosing the Best 1~IVAC System file:///cl/windows/TEMP/0,2637,162$7,( ' 27 Window-Mounted Air Conditioners and Heat Pumps Window-mounted air conditioners and heat pumps cool or heat individual conditioner They have a low initial cast and are quick and easy to install. They are also used to a central heating or cooling system or to condition selected spaces when the central shuts down. When used with a central system, the units usually serve only part of the conditioned by the central system. In such applications, both the central system and units are sized to cool the particular conditioned space adequately without the other In other applications, where window units are added to supplement an inadequate e~ system, they are selected and sized to meet the required capacity when both systerc Window units require outside air and cannot be used for interior rooms. Window units are factory-assembled with individual controls. However, when severs used in a single space, the controls may be interlocked to prevent simultaneous hea cooling. For energy management in hotels, motels and other hospitality applications, on/off control system may be used to de-energize units in unoccupied rooms. Other consider when selecting window unit systems are that window units are built to applio standards, rather than building equipment standards, so they may have a relatively s high energy usage. Through-The-Wall Mounted Air Conditioners and Heat Pumps, PT, PTHPs Through-the-wall air-conditioners, packaged terminal air conditioners (PTACs), heat packaged terminal heat pumps (PTHPs) incorporate a complete self-contained air-a direct-expansion (DX) coaling system, a heating system (gas, electric, hot water, ar controls, and fan in an individual package. They are designed to cool or heat individ~ Each space is an individual occupant-controlled zone into which cooled or heated air discharged in response to thermostatic control to meet space requirements. These systems are usually installed i motels, office buildings, and schools. commercial grade. n apartments, assisted-living facilities, hospitals Units range from appliance grade to heavy-dut Unitary System Selection Guidelines Unitary systems are selected when it is decided that.a central HVAC system is too la expensive for a particular project, or a combination system (central and unitary) is ne certain areas or zones to supplement the central system. For example, unitary syste frequently used for perimeter spaces in combination with a central all-air system thal interior building spaces. This combination will usually provide greater temperature ar control, air quality, and air (conditioned air and ventilation air) distribution patterns, th possible with central or unitary units alone. As with any HVAC system, both the adva the disadvantages of unitary systems should be carefully examined to ensure that th selected will perform as intended for the particular application. Factors to consider when selecting. unitary systems include: Heating and cooling capability can be provided at all times, independent of atl in the building but basic systems do not provide close humidity control. Howe humidity control is not needed far most applications. Close humidity control, if computer room applications or the like, can be accomplished by selecting spe purpose packaged units. Only the one unit and one temperature zone is affec malfunctions. One drawback of unitary units is that the operating sound levels high. Another is that appearance can be unappealing. Other disadvantages ai filtration options may be limited and outdoor air economizers are not always a provide low cast cooling. Also, condensate can be a problem if proper remove provided. Individual room control (on/off and temperature) is simple and inexpensive. H because temperature control is usually two-position, there can be swings in rc temperature. The air distribution can be adjusted by the occupant, but is IimitE airflow quantity is fixed by design. Ventilation air is provided whenever the cor undarnental Series Item :Choosing the Best HVAC System file:///c~/windows/TEMP/0,263 7, I b287,00.h 28 Window-Mounted Air Conditioners and Heat Pumps Window-mounted air conditioners and heat pumps cool yr heat individual conditioner They have a low initial cost and are quick and easy to install. They are also used to s a central heating or cooling system or to condition selected spaces when the central shuts down. When used with a central system, the units usually serve only part of the conditioned by the central system. In such applications, both the central system and units are sized to cool the particular conditioned space adequately without the other In other applications, where window units are added to supplement an inadequate e~ system, they are selected and sized to meet the required capacity when both system Window units require outside air and cannot be used for interior reoms. Window units are factory-assembled with individual controls. However, when severs used in a single space, the controls may be interlocked to prevent simultaneous hea cooling. For energy management in hotels, motels and other hospitality applications, on/off control system_may be used to de-energize units in unoccupied rooms. Other consider when selecting window unit systems are that window units are built to appli; standards, rather than building equipment standards, so they may have a relatively s high energy usage. Through-The-Wall Mounted Air Conditioners and Heat Pumps, PT. PTHPs Through-the-wall air-conditioners, packaged terminal air conditioners (PTACs), heat packaged terminal heat pumps (PTHPs) incorporate acomplete selfi-contained air-c~ direct-expansion (DK) cooling system, a heating system (gas, electric, hot water, or controls, and fan in an individual package. They are designed to cool ar heat individ~ Each space is an individual occupant-controlled zone into which cooled or heated air discharged in response to thermostatic cantrol to meet space requirements. These systems are usually installed in apartments, assisted-living facilities, hospitals motels, office buildings, and schools. Units range from appliance grade to heavy-dut commercial grade. Unitary System Selection Guidelines Unitary systems are selected when it is decided that a central HVAC system is too la expensive for a particular project, or a combination system (central and unitary) is ne certain areas or zones to supplement the central system. For example, unitary syste frequently used for perimeter spaces in combination with a central all-air system that interior building spaces. This combination will usually provide greater temperature ar control, air quality, and air (conditioned air and ventilation air) distribution patterns, th possible with central or unitary units alone. As with any HVAC system, bath the adva the disadvantages of unitary systems should be carefully examined to ensure that th selected will perform as intended far the particular application. Factors to consider when selecting unitary systems include: Heating and cooling capability can be provided at all times, independent of otl in the building but basic systems do not provide close humidity control. Howe humidity control is not needed for most applications. Close humidity control, if computer room applications or the like, can be accomplished by selecting spE purpose packaged units. Only the one unit and one temperature zone is affec malfunctions. One drawback of unitary units is that the operating sound levels high. Another is that appearance can be unappealing. Otherdisadvantages ai filtration options may be limited and outdoor air economizers are not always a provide low cost cooling. Also, condensate can be a problem ifi proper remove provided. Individual room control (on/off and temperature) is simple and inexpensive. H because temperature control is usually two-position, there can be swings in rc temperature. The air distribution can be adjusted by the occupant, but is limits airtlow quantity is fixed by design. Ventilation air is provided whenever the cor Fundamental Series Item : Lfioosing the Best HVAC System file:///cl/windaws/TEMP/0,263 7,16287,C operates but capabilities are also fixed by design. The size of the cooling and coils are also fixed. One manufacturer is responsible for the final unit. Manufacturer-matched con have certified ratings and pertormance data and factory assembly allows imps quality control and reliability. There are a number of manufacturers, so units s available, but equipment life may be relatively short, usually 1p-15 years as ct larger equipment which may have life expectancies of 2Q-25 years. Manufacti instructions and multiple-unit arrangements simplify the installation through re tasks. System operation is simple. Generally, trained operators are not required and mechanical and electrical space is required than with central systems. Howev maintaining the units is more difficult because of the many pieces of equipme location, which is usually in occupied spaces. Initial cost is usually low but operating cost may be higher than for central sys' will be the case when the unitary equipment efficiency is less than that of the system components. Also, energy use may be greater because 'fixed unit size require oversizing for some applications. For applications such as leased offic energy use can be metered directly to each tenant. Units can be installed to c one space at a time as a building is completed, remodeled, or as individual ar leased and occupied. Another energy management opportunity with unitary s~ that units serving unoccupied spaces can be turned off locally or from a cents without affecting occupied spaces. Summary A solid understanding of the various types of commercial HVAC systems and their s• important for the energy manager because the position often calls for being the owns representative to work with others to ensure that the owner gets the environmental s will best flt his needs. Samuel C. Monger, CEM, CDSM, is the principal of the energy systems training firm, Monger Worldwide Consulting. The author of numerous articles and books on perforr testing and evaluation of HVAC/R systems, Monger is a nationally recognized energy systems educator and. enerav enaineerina professional. Copyright ©2000 by Business News Publishin Co. indamental Series Item : Choosing the Best HVAC System filet//c~windows/TEMP/0,2637,16287,OO.h~ 30 operates but capabilities are also fixed by design. The size of the cooling and coils are also fixed. One manufacturer is responsible for the final unit. ManufacturerTmatched con have certified .ratings and perFormance data and factory assembly allovus impl quality control and reliability. There are a number of manufacturers, so units z available, but equipment life, may be relatively short, usually 10-15 years as cc larger equipment which may have life expectancies of 20-25 years.. Manufacti instructions and multiple-unit arrangements simplify the installation through re tasks.. System operation is simple. Generally, trained operators are not required and mechanical and electrical space is required than with central systems. Howev maintaining the units is more difficult because of the many pieces of equipme location, which is usually in occupied spaces. Initial cost is usually low but operating cost may be higher than for central sys~ will be the case when the unitary equipment efficiency is less than that of the system components. Also, energy use may be greater because fixed unit size require oversizing for some applications. Far applications such as leased offic energy use can be metered directly to each tenant. Units can be installed to c one space at a time as a building is completed, remodeled, or as individual ar leased and occupied. Another energy management opportunity with unitary s~ that units serving unoccupied.spaces can be turned off locally or from a cents without affecting occupied spaces. Summary A solid understanding of the various types of commercial HVAC systems and their s~ important for the energy manager because the position often calls for being the owns representative to work with others to ensure that the owner gets the environmental s will best fit his needs. Samuel C. Monger, CFM, CDSM, is the principal of the energy systems training firm, Monger Worldwide Consulting. The author of numerous articles and books on perforr testing and evaluation of HVAC/R systems, Monger is a nationally recognized energy svstems educator and energv engineering professional. Copyright ©2000 by Business News Publishin Co. 31 HVAC System Life Cycle Analysis Richard E. Whiffed and Northern Human Services Buildings County of Orange June 5, 2Q01 EXECUTIVE SUMMARY Purpose Orange County contracted Robson 8~ Woese, Inc. Consulting Engineers to perform a life cycle cost analysis on the replacement of heating, ventilation, and air conditioning (HVAC) systems at the :Richard E. Whiffed Human Services Center and the Northem Human Services Center. The analysis was intended to: mallow the County to select appropriate HVAC systems that :are energy efficient, economical on a life cycle basis, and improve the indoor air quality (IAQ) for occupants and users. preview the existing HVAC facilities construction, determine systems deficiencies, propose and evaluate various HVAC systems as replacement options. The existing systems are approaching the end of their useful lives and replacement should be planned far at this time. Additionally, the building usage and indoor air quality standards have changed dramatically since the systems were installed. The analysis is intended to assist the County The analysis is to be the basis of systems document. in its selection of appropriate HVAC systems. design. It is not intended to be a design Recommendations The Richard E. Whiffed Human Services Center is heated and cooled by a central boiler and chiller plant with a variable air volume (VAV) distribution system serving the main building and the east wing. The Recreation Department building is served by the central boiler. Window units provide cooling for the main floor. The gymnasium is not served with cooling at this time. Robson and Woese recommends providing a new variable air volume system for the main building and east wing, with a constant volume HVAC system for the recreation building. All buildings would be supplied with hot water heating from a central boiler plant and chilled water from a central air cooled chiller plant. The Northem Human Services Center is heated by a central steam boiler utilizing finned tube radiation and unit heaters. Individual window air conditioning units serve roams other than the cafeteria, which has a split system air conditioning unit. Robson and Woese "recommends providing a new variable air volume system for the rooms, with a constant volume HVAC. system far the gymnasium and cafeteria. Heating would be supplied from a central hot water boiler and chilled water from a central air cooled chiller. (31) 32 Evaluation Methods To develop this report Robson and Woese, Inc. reviewed existing conditions by the following methods: • Review and collate existing available plans from all known projects on each site in order to understand systems and proposed construction areas ,Where practical, field verify .and' visually review existing equipment and systems to confirm installed conditions • Based upon the review,. determine systems shortcomings and propose replacement systems • Review the constructability of the proposed recommendations • Provide preliminary opinions of probable construction cost, anticipated annual energy cost, and perform life cycle analyses of each proposed solution as the basis of selection. Our estimates of probable construction cost are based upon construction cost information included in Means Estimating Guide 2000. Please note that no asbestos abatement or hazardous materials were included in construction cost estimates; fio the best of our knowledge, all asbestos abatement 'and hazardous materials work is complete. Median useful life for equipment and systems were obtained from current ASHRAE publications with adjustments where believed appropriate. Fuel costs were obtained from local fuel suppliers as documented in our appendix; fuel costs listed are effective as of the day noted and are subject to change. Uniform annual costs calculated are based on the application of a sinking fund factor to capital cost at a 3% inflation rate and over the median life of the equipment, added to the estimated annual energy cost. . HVAC load and energy cost calculations were made using Carrier's Hourly Analysis Program Version 4.04. The building envelope construction information used for input to the program was obtained from existing available plans and field comparison. Building configuration and intended use was obtained from interviews with County personnel. Energy consumption is based upon current (Whiffed) and eventual intended (Northam) occupancy, current ventilation requirements, and current fuel usage as tabulated in the Appendix of this report. Goals The goals of the new HVAC systems for the Whiffed and Northern Buildings are: - • Improved indoor air quality conditions • Improved comfort levels • Provide the most cost=effective combination of initial, energy, and maintenance costs (i.e., the most economically efficient HVAC systems) • Quiet operation • Remote access/review/troubleshooting of systems • Flexibility to accommodate changing space usage ' • Compatibility with other digital controls (32) 33 O tions For these applications we considered the following HVAC systems: Richard_E~Whitked_Humar~ Services Center • Packaged or Split Direct Expansion (DX) • Water Soun~ Heat Pumps with Evaporative Cooler and Hot Water Boiler • Fan Coil/Unit Ventilator with Air-cooled Chiller and Hot Water Boiler • Multi-zone with Air-cooled Chiller and Hot Water Boiler • Variable Air Volume (VAV) with Air-cooled Chiller and Hot Water Bailer Northem Human Services Center • Through-the-wall Type Packaged Terminal Air Conditioning (PTAC) Units • Packaged or Split Direct Expansion (DX) • Water Source Heat Pumps with Evaporative Cooler and Hot Water Boiler • Fan CoiVUnit Ventilator with Air-cooled Chiller and Hot Water Boiler • Multi-zone with Air-cooled Chiller and Hot Water Boiler • VAV with Air-cooled Chiller and Hot Water Boiler • Packaged Rooftop Type-Multi-zone (PRTU-MZ) • Packaged Rooftop Type-VAV (PRTU-VAV) • Window Air Conditioning System (units) with Steam Boiler and Finned Radiation Heating Thermal Storaae We have considered the use of a thermal (ice) storage system for use at each of the facilities. Our conclusion is that the electrical costs to create ice for storage at night exceeds any demand charge savings under the current electrical power rate schedule. Since it will actually cost mare to operate the system through its implementation, we do not recommend the installation of an ice thermal storage system. This is discussed in mare detail in our analysis. Solar Heating Systems We have also considered the use of solar heating systems for use at each of the facilities. Solar heating could be considered as a supplement to the conventional heating system, but would not be able to meet the entire heating needs at either location. Our conclusion is that the initial capital costs to install a solar system would not provide a payback within a reasonable period of time. Also, solar heating is best incorporated into a building during the initial design. A design approach that considers the whole-building design would consider solar heating within the context of the entire building envelope, including windows, daylighting, and the HVAC system(s). Orange County may wish to investigate solar heating fvr domestic hot water needs, especially at the Northern Center. The following pages provide descriptions of each of the systems considered. (33) 34 Systems Eliminated Several systems were eliminated from further consideration. Because of higher energy and maintenance costs, and the inability to meet necessary indoor air quality standards, the PTAC and DX systems were eliminated from consideration. The WSHP and unit ventilator/fan coil systems were eliminated ,due to their inability to adequately satisfy all indoor air quality requirements, particularly in small, compartmentalized rooms. Thus, our " ~shortlist" of considered systems was reduced to the multi-zone and variable volume systems for each building. Recommendations Whiffed Building For the existing building construction and use, we calculated a maximum cooling load requirement of approximately 200 tons (Tons is a unit of measurement for determining cooling capacity. One ton equals 12,000 Btuh). For either amulti-zone or VAV system, the cooling source will be an air-cooled chiller; the air-cooled chiller will provide chilled water at a similar overall system efficiency as awater-cooled. system, while reducing component numbers and- maintenance ,cast. With natural gas readily available, the heating source will be two (2) natural gas-fired hot water boilers. A comparison of the two proposed systems is as follows: .System ° r~PGbahle : ; Energy imple l~niform -. , :Median `- ,, pesCriptiOn Construction~:~ Costs Payback, Annual Cost ' Useful ,; ,..' ' Cost ($) ($)/year. years ; ($) ' S stem.L~fe. y k 4 i:~ ~fy?`! /.~., ~~.lal wl Multi-zone, Air- cooled chiller and natural gas $1,204,900 $60,900 N/A $105,800 20 boiler 1lA ,,;per cr5~fe~ ' ~. s s- ~' S t j f ~ ~ ~ ~ , " :ch~~l~1~.andl+y~{~Y"Y1 ` a ural# ~ •.~ 1'~;.~ r' ",'ii .. ~4 ~~.i i ~. ' ' , •: ,4 , ~ jl. ;.~~4 ~1. ~~~i ;G:; ,~tr~~~~~ 4 ;' r ~ ' jai ~~ ~ ~ .x ''~,,,~ r, . ;L ~ ~ ~ n t gas ~„r., ~ ~ ,~ ' ~ ~ r . ~' ;$;11;`309,200 ~ , r ; .~: ~... y ~r~ .8r~": ~ r ~~'~9r3~ ~ ~ ~ ~, ~ . r boiler ,. ~:~ ~ , • ,- ,,~ ; ~'Recommer?dedY$ sta , .p~ ~ - ~, We recommend the insfallation of a variable ar'r volume system with terminal reheat for the Whined Building based an uniform annual cost. Coaling source will be an air cooled water chiller to replace the exisfing water-cooled unit. (34) 35 Northern Building Based upon the existing building construction and intended use, we calculated a maximum cooling load requirement of approximately 110 tons. Like the Whiffed Building, our general HVAC system alternatives considered were the multi-zone and VAV systems. With no natural gas readily available, alternate bailer fuels considered were fuel oil (existing source) and propane. No simple payback was calculated for the Northern Building HVAC system due to the significant differences in median useful life. Our analysis, therefore, is based upon uniform annual cost including initial and energy costs. The results of our analysis of the proposed systems are as follows: System Description Probable Energy Uniform Median , :. Construction Costs ($) Annual Cost : Useful, Cost (S) ($),.', System Llfe ' ' , ears Multi-zone, Air- cooled Chiller and Fuel Oil Boiler $621,700 $37,100 $60 200 20 Multi-zone, Air- cooled Chiller and Pro ane Boiler $613,200 $58,500 $81,300 2p VAV, fiir~ooled 4h71er and Fuel`Cti _ - _ ~ y ~ A ~' ~ ~ '~ ' " ~, ,' _ y,~~. ! ISy- "~~~ -t '`ky F .:~.BDiler': $603 900 ~3 ~ 4 . .$ -100 ~- ~ ;$0'b ~ , ~ ~ ~~~~,~~':~ ~0~: VAV, Air-cooled Chiller and Propane Boiler $595,400 $34,800 $57,000 20 PRTU-Multi-zone $521,300 $57,200 $85,300 15 PRTU-VAV $506,200 $33,200 $60,400 15 PTAC $328,140 $26,800 $69,200 6 Window AC 8 6 (window AC) Steam Boiler $464,660 $24,200 $57 700 20 boiler Both the PTAC and Window Units/Steam. Boiler Systems have been added for comparison purposes, however they do not meet Indoor Air Quality standards. Although initial costs could be reduced significantly using packaged rooftop equipment, the longer service life expectancy of the boiler/chiller-based systems make them the more attractive choice on a uniform annual cost basis. We recommend the installation of a new HVAC system generally consisting of a variable air volume HVAC system with terminal reheat, utilizing an air cooled chiller and oil fired boiler based on uniform annual cost. (35) 36 Packaged Terminal Air Conditioners (PTAC) We considered the installation of units similar to the typical "through-the-wall° units used for conditioning motel rooms. Advantages • Ease of installation - • Lowest installed cost • Individual room/unit control • ,Modular application for individual rooms • Well suited where systems perFormanc~ requirements are minimal Disadvantages • Highest energy cost • Increased electrical service required per installed refrigeration capacity • Limited installation location to outside walls • Median useful life only 6 years • Highest maintenance cost • No indoor air' quality improvement due to lack of outside air control and low air filter efficiency • Least amount of control over building temperature and humidity levels • Noisy • No ability to troubleshoot systems remotely • No capability to be modified for revised space usage • ,Ability for ~nnection to reGnote digital controls limited to "on-ofP' service only. An illustration of a typical system follows. (36) 37 Packa ed Direct Ex ansion DX and S lit DX S stems Another commonly used, low installed cost option would be the installation of packaged or split DX systems similar to residential-style systems. Under this option, the refrigeration equipment would be placed outdoors with ductwork routed into the building, or multiple small mechanical closets would be created for air handling equipment. 4dvantages • Low installed cost - • Improved ventilation control over the PTAC system • Lower energy cost than PTAC • Improved temperature control over PTAC • Quieter than PTAC Aisadvantaaes • High energy costs • Increased electrical service over central systems • Median useful life of 15 years • High maintenance costs due to large number of refrigerant systems • Low air filtration efficiency available and fixed outside air will not permit adequate indoor air quality control • Inadequate control over humidity due to cycling service of refrigerant systems . • Noise level of equipment readily noticed in occupied space near equipment An illustration of _a typical system follows. SpNt Syshm wI~ DX Cook Ar•a: ~ ~,Mre III: 0.00 APPS CAV arp Ai, OX 2 0p, Oar llut Typical OF. 1 ~. ~.~ ~u07up r)P• ~ Type ~12 « - i w r ~a• ~ Qac Mai[ ~pe G Fpr S4 1 DD SoKa ~p ~ n p ~ a 0 N ~ pa 0 JII• twrgaen AI S~gpb' Fri 00 Fir Oily AIMm p _ I.c. Tamparaxra Oaaiepn TArmppr p Rll~en Smote Dat•ppr DI 8~~py Fn Red DI Svppp Srnot• Dttrdor W (37) 38 Water Source Heat Pum s SHP We considered ceiling-mounted water source heat pumps. One heat pump would be provided far each individual temperature control zone, and would provide the heating/cooling equipment, as well as air distribution equipment within each unit. Heat addition or rejection would be from a piped water supply; which in tum, would be heated or cooled by a hot water boiler or fluid cooler (similar to a cooling tower). . Advantages • Energy efitcient • 19 year median useful life • Multiple units provide good zone temperature control Relatively quiet in small sizes • Remote access available for control and troubleshooting • May be connected with other centralized digital controls Disadvantages - • Higher maintenance costs due to large number of refrigerant systems • fixed outside air and low filtration efficiency will not permit adequate indoor air quality control • Minimal control over space humidity The fallowing is an illustration of a typical system: Yftitrr Sores Mat Prr~ ~ wrrr aer+e~ Hwe run~a• ~ ~ aoo Applla~pe~ F1r~1 P~rfq. t CoRq. M~I~.b. AU- 7ypiea~l Ok 1 ww eaw ~ ~ ` '~+. ~. M ~..° ~~ K I~A'i r. i a 1t ..y ~~~ ~ ~ ~ ~ N N ~~ 0 0 DC! g Sp1o~ T~M~ gMP~x N d ~a Sbpr + oD MI/R (38) 39 Unit Ventilator/Fan-coil System Under this option, central hat water boilers and a chiller would be provided far heating and cooling sources. Small cabinet fans enclosed with cooling and heating coils would provide air distribution. This type of system provides relatively efficient and low maintenance operation, but uses the same low efficiency filtration of the DX equipment. Advantages • Energy efficient • Over 20 year median useful life • Good temperature control • Low maintenance costs due to central chiller and boiler systems • Relatively quiet operation • Remote access available far control and troubleshooting • Can connect with other centralized digital controls Disadvantages • Relatively high installed cast • Fixed outside air control (fan coils) and low filtration efficiency will not permit adequate indoor air quality control where fan coils are installed • Minimum control over space humidity • Difficult to modify for revised space configurations and usage The following is a typical illustration of a fan-coil system: F~ CaN Hweh~oW~p Sysb~r~ ~ F.cesr.w. sew aoo App~011. FNI ~ INw * F~- hl1d, 4 Pq 0001 Or MBA ~~ ~ ~ GMwr~ CMYM! r~r~ ~rnre `° ~ ~.{~ 11~ VMr~ p ~ Tw~MM~ ~ N . i~ OO F~ Pieel p I~Nt Or~~ d (39) 40 Multi-zone System A multi-zone system is an HVAC system that distributes a constant volume of air to each conditioned space from a central location. Using a water chiller and hot water boiler as the cooling and heating sources, it would simultaneously provide cold and hot air, and. blend this air using mixing dampers to satisfy space temperature conditions. Advantages • Over 20 year median useful life, • Low maintenance costs • Goad control over indoor air quality with outside air ventilation control and high filtration efficiency • Good control aver space temperatures and humidity levels • Quiet operation • Remote access available for control and troubleshooting • Can connect with other centralized digital controls • Systems may be modified to accommodate revised space configurations and usage Disadvanta es • High energy usage due to simultaneous heating and cooling • Relatively high installed cost Packaged Rooftop-Multi-zone A variation on these systems is the installation of packaged rooftop source equipment in a multi-zone configuration. Self-contained DX equipment would replace the water chiller and a gas furnace would replace the boiler as source equipment. The packaged rooftop multi-zone system would have a lower installed cost than the chiller/boiler based system but would have a shorter median useful life of 15 years and a high energy usage and cost. The following is an illustration of a .typical multi-zone system: ~x,~~. N.~.~~ncoon~ sycw„ ApyleNien: GW r~I1~F, lawl pX 2 ap ~ TfPkM GC 7 .., . ,L,. ,. a~~ ~, :': ~. _, ,~. ~~ 7~ ~+ rYo~ ~yq ~p ~~pp AE1 ~npRM~n T N N ~ nw- ~pwiW~ ~ ~~= ~ ~ N R ~rn ~ 6uap~Fm UO FMrpMq AYm~ p I,qr Tw~4walu~ OMR'!bl T~wnu!/ ~ p p~WnF~A~ d RMUn3mak~DwcV ~ p &~~ q j S~sOb OlMeer (40) 41 Variable Air Volume A S stem A variable air volume system is an HVAC system that, like the multi-zone system, distributes conditioned air from a central location to each space according to the amount of cooling or heating necessary to each space. A central air-handling unit would provide primarily cold air through ductwork for cooling and dehumidification purposes, while duct-mounted hot water coils at each conditioned space provide heating. Advantages • Over 20 year median useful life • Low maintenance cost • Low energy cost • Good control over indoor air quality with outside air ventilation control and high filtration efficiency • Good control over space temperature and humidity levels • Quiet operation • Remote access available for control and troubleshooting • Can connect with other centralized digital controls • Systems may be readily modified to accommodate revised space configurations and usage Disadvantages • Highest installed cost Like the multi-zone, a variation would be the installation of packaged rooftop source equipment in a variable air volume configuration. Self-contained DX equipment would replace the water chiller and pumps and a gas furnace would replace the boiler as source equipment. This would reduce the installed cost but would result in a shorter median life of 15 years and higher energy usage and cost. The following is an illustration of a typical VAV system: VAV Ttu~nlnd with A~ VWITrnMW•rA1W~ 81s: 0.00 App1IC~tl0~k VAV Oa wV Ilpt YM1M RMrM .TYP~~ Of: t . N~ MNIR F1WIE TJ'p• T~q ~ ~ ~ 8p~o~ T~~rr N S~AF1~~ M IpOht CnuekY 01 (41) 42 Window Air Conditioning System with Steam_ Boiler Radiation Heat Window Air Conditioning systems are Direct Expansion (DX) cooling units that supply conditioned air to each space for cooling. For heating, a steam boiler would supply radiation-type heat exchangers in each space. This system is similar to the current HVAC system in the Northern building. Advanta es of Window Air Conditio i S stems • Low initial cost • ,Moderate operating cost • Individual zone control • No piping/supply ductwork required Disadvanta es of Window Air Conditionin S stems • No economizer cycle • Many points of electric power wiring • Mechanical noise in occupied space • Poor air filtration _ • Poor ventilation • Negative appearance • Median useful life of 6 years • High maintenance Advanta es of Steam Boiler R diatio Heat • Few points of electrical connections • Low operating cost • Individual zone control Disadvanta es of Steam Boiler Radiatio e • High installed cost. • Poor indoor air quality • Negative appearance • High maintenance cost This system will provide individual zone control, however will provide poor interior air conditioning and exterior aesthetics. The number of Window Air Conditioning units required for each space depends on the size and load of the space. The installed cost is low far the cooling, but has a median .life of only 6 years. The heating system includes a new steam boiler, new condensate pumps, piping, and controls in each space. The following is an illustration of a typical Steam Boiler system: S'~w111 Flrnub• H•aNnp era: srorm~.~ud.wrFq sus: a.o0 Mauuuac waaaen.zaso ryp~ar. ~~ ow,ws nm• maup nm. HeYYq VaM AO 6S6p~pa~oe TarnnPqefra~luurt~ N Ngm~R OI (42)