Evaluating Variable Air Volume (VAV) Packaged Rooftop .

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Carrier Engineering NewsletterVolume 6, Issue 2Evaluating Variable Air Volume (VAV) Packaged RooftopSystems for Use in High Performance EnvironmentsNew codes and energy regulations have changed the standard for packaged rooftop unit construction.Packaged rooftop innovation over the last several years has made a huge impact on the overall efficiencyof these systems and has introduced a shift in design for high-performance small commercial buildings.Owners and occupants of these buildings demand energy conservation and exceptional comfort conditions.High performance buildings that are smaller in size and/or consist of one level often sacrifice energyefficiency and comfort. One significant innovation is the use of Variable Air Volume (VAV) systems insmaller rooftop units to meet today’s aggressive energy strategies and provide a high level of comfort.This newsletter provides an in-depth look at five HVAC systems designed for high performance environments,followed by examples from a prototype office building configured to simulate conditions in four differentclimate zones.Why are packaged rooftop unitsso popular?A packaged rooftop unit (RTU) is one of the most importantpieces of HVAC equipment for providing thermal comfort toan environment that is changing daily as well as yearly. Inaddition, the RTU must be applied across all climate zonesand many different building types. The RTU provides what theInternational Energy Conservation Code (IECC) refers to asa “Simple HVAC System.” The RTU system delivers heating,cooling, and required space ventilation to various zones fromone single source.Why VAV?HVAC systems deliver thermal comfort to an environment asit changes daily as well as over the course of the year. If BTUefficiency is to be achieved through modulating the HVACsystem,maintaining specified set points is not enough. Efficiencyis also affected by control response and turndown efficiency.Using a zone to link spaces with similar thermal requirements,then linking multiple zones to an HVAC system network,allows water or air delivery temperatures to be efficientlycustomized for each zone. The overall efficiency of theHVAC system can be further increased by turndown fromfull-load source capacity to lesser part-load amounts.Usingthese strategies with a VAV system helps to provide improvedthermal environmental control per ASHRAE 55 and betterenergy strategies per IECC 2015. Carrier Corporation 2018www.carrier.com/commercial

Originally when RTUs were introduced to the industry, thepackaged rooftop unit was provided with a single spacethermostat for a single zone. The obvious drawback to thistype of control system is that RTUs don’t serve single zones,they typically serve multiple zones. On a single zone system,the only space that would receive comfort from the HVACsystem was the one that contained the thermostat. Anyadditional zones served by the RTU didn’t have their ownspace temperature sensor and their comfort was basedon the conditions of an external space. In addition, thepackaged rooftop unit often had minimal stages of coolingand heating capacity and operated at constant airflow. Inthis scenario, even the space that contained the thermostatexperienced times where the conditions were uncomfortableas the equipment cycled on and off. Furthermore, the onand off cycling of the cooling system causes the humiditylevels in the space to rise and fall, adding to the discomfort.additional energy savings. The comfort and energy savingbenefits to upgrade from a single zone system to a VAVsystem traditionally outweigh the small additional first costs.Quantifying Energy RequirementsConstructing a zone’s thermal comfort quantityStart by looking at the three basic pillars—Ventilation, BuildingEnvelope, and Internal Loads. These three pillars requirethermal conditioning based upon the zone-required temperatureset point, indoor air quantity, and occupant activities.For example, consider an office building that has thefollowing typical spaces:An upgrade to the single zone packaged rooftop unit wasthe implementation of a VAV system. Similar to a singlezone system, a VAV RTU system has supply air distributionductwork, and air distribution in the space. Instead of a motorstarter, a variable speed drive has been added to the supplyair fan. Instead of one space sensor there are multiple spacetemperature sensors serving multiple zones. For each zonethere is an associated control damper (known as a VAV box).The zone damper, serving its individual spaces, modulatesopen or closed based on the input from the space temperaturesensor. As the zone dampers open and close the staticpressure in the supply ductwork changes. A static pressuresensor detects these changes and sends a signal to theVFD on the supply fan to change its speed/airflow higheror lower. The VAV system has an upgraded control system,but it would still be considered a simple HVAC system. Thesupply air from the rooftop unit is maintained at a constanttemperature, in the approximate 55 to 60ºF range. If a spacerequires cooling it accepts this cool air. If a space requiresless cooling, or heating, the first step is for the VAV boxto reduce the airflow; if additional heating is required anauxiliary heating device is staged on. With VAV systems,each individual space almost never experiences situationswhere its space temperature can’t be satisfied. In addition,a VAV system provides better thermal comfort than a singlezone system because of the additional stages of airflow,heating and cooling.ZONE-1INTERNAL OFFICESZONE-2CONFERENCE ROOMZONE-3COPIER ROOMZONE-4SERVER ROOMZONE-5BATHROOMZONE-6The first step is to evaluate the amount of cooling load requiredat peak design cooling conditions. With this information youcan determine the maximum size of the HVAC equipment,and then if necessary downsize it by applying diversity factors.Look at the minimum design of thermal requirements aswell as the transition between seasons, to see how the zonerequirements associated to the thermal quantity modulateover dynamic ambient conditions. This will provide insight onwhat needs to be monitored by the modulation. It will alsoprovide the minimum and maximum airflow that willbe required to select a VAV box.A VAV system is a powerful tool for balancing indoor airquality and energy reduction. It matches the reduction of cfmprovided by a central supply, relating to reduced rpms thatcapture the power reduction from the fundamental Ideal FanLaw 3. Using the same duct static pressure sensor as aVariable Volume and Temperature (VVT) system, a VAVsystem modulates the variable frequency drive applied tothe central supply fan(s).Building on the foundation of the above objective by theevolution of the packaged rooftop unit and its rich rootedhistory in thermal quality and efficiency, we now look to theenacting of code requirements supporting progress. A deeperdive into efficiency code requirements will enhance rooftopunit system capability to deliver airflow at the most efficientthermal delta T and kwh/cfm.With a VAV system, the RTU can maintain thermal comfort inmultiple zones with diverse conditions while reducing energyconsumption. Simultaneous heating and cooling is available.Varying the volume of airflow to a particular zone to maintain achanging thermal requirement allows for reduced fan energyat the source. In addition, turning down stages of heatingand cooling capacity in the rooftop unit also reduces energyconsumption and maintains thermal comfort across all of thezones in any condition.Moving from ASHRAE 90.1 Standards to enacting thosereferences to code is where the International Energy EfficiencyCode (IEEC) becomes important. Most states use theIECC 2009 version or later as an Efficiency Code, beyondindividual local developed codes, as well as ASHRAE 90.1In summary, VAV systems are an essential upgrade whenimplemented in high performance environments becauseof the additional thermal comfort they provide as well asEXTERIOR WALL OFFICES2www.carrier.com/commercial

Standards. It is this common combined code that developstwo pathways: equipment efficiency stated by ASHRAE 90.1,and an HVAC system approach to energy strategies.Another important aspect of the IECC is Economizer Fault,Detection, Diagnostic protection, in section C403.2.4.7.This section emphasizes that even with the proper energystrategies for an HVAC system, particularly associated witha VAV system, proper maintenance is required to ensurethe energy reduction through the life expectancy. It is criticalto have proper sustainability like the mandated EconomizerFault and Diagnostic with a VAV System based on ProperDuty Cycle. Cooling and heating stages must be based onactual real-time MAT, without false loading or over-ventilatingwhich could hamper IAQ based on relative humidity ranges.IECC 2012 System EfficiencyIn section C403.2.10.1 of IECC 2012, Variable Speed Driverequirements need to be implemented onto a supply fan fora simple or complex HVAC system when that fan is greaterthan 5 HP. The supply fan is not associated to an equipmenttype such as Air Handling Unit, Fan Coil Unit, or PackagedRooftop Unit; instead the fan efficiency has been movedto its own referenced efficiency table C403.2.10.1(1).Furthermore, this applies to a signal zone1 application, whichenacts transition to the code efficiency implementation inIECC 2015 for multiple zones.Summary of Five HVAC SystemsAnother IECC 2012 system energy strategy was economizerrequirements based on climate zone.2 By defining therequirement around climate zones, the previously untappedambient condition can be used to help condition the internalspaces. This also provides a platform for looking at VAVsystem discharge air temperatures to be changed from staticdesign day conditions to dynamic interaction of BTU makeup.These systems were selected for the evaluation becausethey were considered to be the most common choice forthis type of small, single-story, high performance building. Inaddition, they offer similarities as well as major differencesthat should be carefully considered when choosing anappropriate HVAC system. There isn’t one type of HVACsystem that satisfies all requirements and scenarios; forthis application other HVAC systems could be applied.IECC 2015 System EfficiencySystem 1 Single Zone Gas RTU with EconomizerIECC 2015 continued the progression of emphasizingenergy reduction for HVAC systems with the VAV systembased on an air system serving multiple zones, thereforedirectly affecting all HVAC systems based on multiple zones.Most mid-tier efficiency Packaged RTUs with a VVT systemcan meet the requirements with a two-speed variablespeed drive.3System 2 VAV, Gas Preheat RTU with Economizer;VAV Boxes with HW Reheat Coils,Condensing BoilerSystem 3 VAV, Electric Preheat RTU Units withEconomizer. VAV Boxes with ElectricReheat CoilsA further emphasis on saving energy from a BTU associatedreduction of what modulates from worst case (static) to everyday aspects (dynamic) is Demand Controlled Ventilation.Section C403.2.6.1 requires DCV for areas that service anarea greater than 500 ft2 or more than 25 people / 1,000 ft2.This reinforces two things about ventilation: the high percentageof BTUs associated to quantity of the entire heating/coolingcapacity, and how incremental reduction will reduce fanenergy as much as thermal source.System 4 Air-Cooled, Heat Recovery, VRF Systemswith Independent DOASSystem 5 Boiler/Tower WSHP System withIndependent DOAS1Signal Zone is defined by an area experiencing the same building environmentand usage/schedule.2Climate Zone reference table is C403.3.1(1).3A two-speed drive is synonymous with Stage Air Volume in coordination ofstaging on heating and cooling capacities.3www.carrier.com/commercial

Table 1 shows a comparison of the five systems thathighlights some of the main concerns of owners, designers,occupants, installing contractors, and maintenancepersonnel. Each of the considerations was ranked on ascale of 1 to 5, with 5 being the highest and one being thelowest. There is a short explanation in the notes section toclarify certain rankings. Once again, there are many itemsto consider when evaluating different HVAC systems fordifferent buildings and the results can be very different fromthe previous project.Table 1: HVAC Systems Comparison ChartCONSIDERATIONSYSTEM 1 –CV RTUSYSTEMS 2 and 3 –VAV RTU(see note 9)(see note 9)SYSTEM 4 –VRF DOASSYSTEM 5 –WSHP DOASI. OCCUPANT COMFORTTEMPERATURE COMFORTHUMIDITY COMFORTSIMULTANEOUS HEATING AND COOLINGSPACE ZONING(see note 4)INDOOR AIR QUALITYREDUCTION IN OBJECTIONAB LENOISE(see note 8)II. COSTS (see note 4) (see note 5) (see note 6)OPERATING COSTS SERVICE AND MAINTENANCE COSTS INSTALLATION COSTS (FIRST COSTS)III. OTHEREASE OF START UP AND OPERATIONEASE OF MAINTENANCEEASE OF FUTURE REPLACEMENTFLEXIBILITY OF INSTALLATION(see note 7)Each oftheObservations:considerations were ranked on a scale of one to five, with five being the highest and one being the lowest.Notesand1. Other HVAC systems that could be considered for this application: a) fewer, larger VAV rooftop units, b) fewer, larger commercial split systems with VAV control,or c) numerous, small residential split systems.2. A DOAS system for System 4 or 5 can vary greatly in nature. Some options for its design could be: a) providing untreated outside air directly connected to theterminal equipment, or b) a simple energy recovery device with only fans, or c) a high end heating/cooling system tied into the VRF or WSHP system. There arealso many intermediate offerings between these simple/inexpensive or complex/expensive systems.3. Life cycle costs are an important factor but were not considered in this evaluation. In addition, such a detailed analysis is not normally performed on this typeof small project with simple HVAC systems and with relatively short design and construction periods.4. The most common system provided is single zone RTU.5. Because of the higher first cost of VRF systems, often the number of fan coils and zones on a VRF system is reduced when compared to a VAV system.6. For the application in this newsletter (approximately 80-120 tons) typically a WSHP system would have the highest first costs.7. VRF systems have the greatest amount of flexibility due to the different types of FCUs available as well as the flexibility on selection a location for the condensing units.8. Indoor sound quality is probably equal for Systems 1 through 4, but the VRF system has the quietest sound levels due to its condensing unit.9. Packaged RTUs can add dehumidification control to their system for enhanced humidity control.4www.carrier.com/commercial

The chart does not give weighting factors to everypossible item because each HVAC system has uniquestrengths and weaknesses that can be matched to theindividual requirements of the building construction, ownerpreferences, location, etc. Lowest first cost is often themost critical factor when selecting an HVAC system, butlow first cost frequently results in insufficient occupancycomfort, higher energy costs, and higher maintenancecosts. In this evaluation, System 2 and 3 (VAV RTU) andSystem 4 (VRF with DOAS) are slowly making inroadsin the industry when compared to System 1 (CV RTU).Designers and owners are the driving factor for thisincrease in usage because they want to provide additionalcomfort to occupants. The ability to provide simultaneousheating and cooling to an entire building is an easy solutionfor minimizing occupant complaints. Furthermore, theever-increasing code requirement for energy reductionalong with increasing indoor air quality standards isstraining the ability of the CV RTU to be a viable systemin the future. Surveying the industry, it seems mostdesigners and owners at this time are leaning towardsproviding System 4 (VRF with DOAS) as an upgrade toSystem 1 (CV RTU). It seems that System 2 and 3 (VAVRTU) is being overlooked as an upgrade for CV RTUsystems. In a broad evaluation, when VAV RTU is comparedto VRF with DOAS, VAV RTU is often lower in first cost,equal or better in energy usage, and easier to install andmaintain. Other benefits of a VAV rooftop system for small,high performance buildings are described below.DOAS system for VRF and WSHP systems can haveenhanced filtration, but the terminal equipment at the zonelevel for these two systems is limited in the amount offiltration that can be provided.Simple, traditional HVAC systemThe main equipment component of a VAV rooftop systemis the packaged rooftop unit. This piece of equipment isa tried and true pillar of an HVAC system, one that hasbeen around for many years and is familiar throughout theindustry. The installation, operational, and maintenancerequirements of the RTU have not changed much from itsinitial introduction many years ago. VAV boxes are simpleto install and operate, and they require little maintenance.The use of a ductwork system and the overall controlsystem are likewise similar and consistent in installationoperation and maintenance requirements.CommissioningA VAV rooftop system doesn’t require special trainingor extensive time to perform check/test/start-up as wellas commissioning. Today’s VAV control systems for therooftop unit and VAV boxes are factory-installed andare typically plug and play with auto-discovery andpre-determined control algorithms.Service, maintenanceWith a VAV rooftop system, work (including filterreplacements) takes place outside of the occupied areaand does not disrupt the occupants. In addition, thesystem is simple enough that a larger base of availableservice technicians would be qualified to work on it.Because WSHPs are open to the atmosphere, thesesystems would have the highest maintenance costs.Additional dehumidification controlA dehumidification control system is available as a factoryengineered and installed option on packaged rooftopunits. In applications where buildings or zones are subjectto higher than normal latent cooling load conditions,the addition of a dehumidification system could provideadditional space comfort for the occupants. When theoutside air or the zone contains higher than acceptablelevels of moisture, a humidity sensor would trigger theoperation of either:Equipment life expectancyThe life expectancy of any HVAC system is highlydependent on the quantity and quality of service andmaintenance. Ductwork systems traditionally have alonger life expectancy versus piping systems. Systemsthat operate their compressors in an on-off fashiontypically have shorter life spans. Systems that operatetheir compressors in heating and cooling typically haveshorter life spans versus cooling only systems. latent cooling operation or neutral air operation in the rooftop unitEase of future replacementReplacing a rooftop unit requires integration with theexisting support system as well as the control system.Replacing a component in a VRF system requiresintegration with the existing refrigerant piping systemas well as the control system. Replacement of WSHPsis simple; they traditionally include isolation valves andhose kits on the piping connections.This dehumidification system is an inexpensive optionthat doesn’t require any special field modifications andhas been available in constant volume units for years.Improved indoor air qualityPackaged rooftop units have the ability to incorporatehigher levels of filtration versus the tradition MERV 8 rating.In addition, IAQ would be improved during economizeroperation because of the increased amounts of outsideair brought into the building. Further improvements to IAQcould be realized with the implementation of a demandcontrol ventilation (DCV) system with the use of CO2sensors. In addition, a DCV system would save additionalenergy by preventing over-ventilation of the spaces. TheComfortA VAV rooftop system can provide simultaneous heatingand cooling operation similar to a VRF and WSHP system.Because it contains multiple space sensors, additionalcapacity stages, and VAV boxes, it provides better temperatureand humidity control than a single zone system. Additional5www.carrier.com/commercial

comfort can be provided by the simple addition of adehumidification system. A supply air temperatureand static pressure reset system would also enhancethe building’s comfort by providing more stableoperating conditions.Source EUI accounts for the inefficiency of generatingand transmitting electricity. Source EUI is more meaningfulto someone concerned about global warming since it isa true measure of environmental impact. Source EUIincreases the EUI for electricity by a factor of about3 since average electricity generation and transmissionefficiency is about 28%.First costsSystem 1 (CV RTU) rates 5 stars since contractors andtechnicians are familiar with the system requirements,and the equipment cost of the rooftop equipment is lowerwhen compared to the equipment in a VRF system andthe DOAS unit. VAV rooftop units are traditionally verycompetitive with other HVAC systems across manydifferent building types, applications, and locationswhen comparing first costs.Low energy costsVAV rooftop units are traditionally competitive with otherHVAC systems across many different building types, buildingapplications, and locations when comparing energy costs.Operating costs for rooftop units are traditionally lowestwhen an airside economizer can be effectively utilized.In addition, operating costs of a rooftop unit are greatlyenhanced when there is a larger percentage of heatinghours and gas is the preferred utility (instead of electricheating). Furthermore for VAV rooftop systems, duringoperation at part load conditions a supply air temperaturereset and static pressure reset system must be providedto satisfy energy codes. Although these two additionalenergy saving measures traditionally are overlooked, theyare easy to implement; the control devices are alreadyincluded in the base system and the programming logicis already included in the controller. These two controlsequences save additional fan energy as well as cooling/heating energy. VRF and WSHPs also have low operatingcosts based on their ability to transfer energy between zones,but not having an economizer system is a disadvantage.SoundBecause the compressors are located inside the buildingon WSHP systems, objectionable noise can sometimesbe a problem. VAV rooftop units are traditionally quietand are located away from the occupancy spaces.Global WarmingThe EUI (energy use intensity) for the entire buildingis shown on Figure 2 bar charts in the energy analysissection of this newsletter. The cities chosen were Houston,Los Angeles, Philadelphia, and Chicago. The EUI value isrepresented in kbtu/sq ft per year of total building energyconsumption; it also includes lights and plug load energyconsumption. As you will see, VAV rooftop system havecompetitive EUI values when compared to other highperformance systems. Please note that electricity canbe generated at the site or the source (power plant).6www.carrier.com/commercial

Energy SimulationAn energy simulation was performed for the five different HVAC systems across four different climate zones. Below isa brief description of the general features for all models as well as additional details of each of the five systems.HVAC Systems:General Features of All System Models: 75 F/70 Foccupied thermostat setpoints 80 F/65 Funoccupied cycle setpoints ASHRAE 90.1 office operating schedule VentilationASHRAE 62.1-2013 ventilation rate procedure (effectiveness, people diversity, critical space included) Utility RatesState average prices compiled by US Energy Information Admin (EIA)System 1 Single Zone Gas RTU Units Houston, Los Angeles and Chicago comply with IECC-15. Philadelphia complies with IECC-09. 10 units one per thermal block Stage air volume operation: 2 speed cooling, 1 speed heating Outside air: Integrated enthalpy economizer Gas heat RTU compressor and outdoor fan from product selections 57 F design supply air temp to buildingSystem 2 VAV RTU Units Gas Preheat-HW Reheat Coils, Condensing Boiler Houston, Los Angeles, and Chicago comply with IECC-15. Philadelphia complies with IECC-09. 2 units each serving 2 perimeter thermal blocks 2 units each serving 3 interior thermal blocks Outside air: Integrated enthalpy economizer Gas heat in rooftop unit RTU compressor and outdoor fan from product selections 55 F discharge air temp Variable air volume operation: Forward curved fan with VFD 30% min VAV box position 95% efficiency natural gas HW condensing boiler for reheat coilsSystem 3 VAV RTU Units ELEC Preheat and Box ELEC Reheat Coils Same as System 2 but electric resistance heat throughoutSystem 4 Air-Cooled, Heat Recovery, VRF Systems with Independent DOAS Houston, Los Angeles, and Chicago comply with IECC-15. Philadelphia complies with IECC-09. 2 separate air-cooled heat recovery VRF systems 5 thermal blocks each Each VRF fan coils served by DOAS Outside air: DOAS, 60% ERV, gas heat, electric cooling Electric supplemental heat if required VRF ODU variable speed rotary compression ODU and outdoor fan kW from product selections 57 F design supply air temp indoor terminal units VRF fan coil: Low static 0.3 in. TSP cassette type non-ducted VRF system has 140 feet indoor/outdoor separation, 15 feet verticalSystem 5 WSHP System with Independent DOAS Closed loop, reverse return piping system, water source heat pump system Outside air: DOAS, 60% ERV, gas heat, electric cooling Heat adder, gas boiler, 95% efficiency Heat rejector, cooling tower, 0.05 kw/ton VFD fan Loop range 68 F to 86 F high, pump 30 ft wg, 3 gpm/ton WSHP energy efficiency ASHRAE 90.1-2013 compliant 57 F design supply air temp indoor terminal units Water source heat pumps: Medium static 0.6 in. TSP, horizontal type, ducted7www.carrier.com/commercial

Building TypeThe building used for the simulation was patterned after a Prototype Pacific Northwest National Laboratory (PNNL)office building. See Figure 1.Figure 1: Modified DOE Benchmark Building – Medium Office V3Core Cube 11,800 sq ft15 Ton LoadCore Cmp 3,600 sq ft7.5 Ton LoadCore Cmp 3,600 sq ft7.5 Ton Load185 ftCore Cube 11,800 sq ft15 Ton LoadEast Perimeter 3300 sq ft7 Ton LoadWest Perimeter 3300 sq ft7.6 Ton LoadNorth Perimeter 5200 sq ft8.4 Ton Load280 ftCore Food 2,000 sq ft7.4 Ton LoadCore Food 2,000 sq ft7.4 Ton LoadSouth Perimeter 5200 sq ft8.8 Ton LoadGrand Total Area 51,800 sq ftTotal for building is 90 tonsBuilding Features: Rectangular shape; 1.5 aspect ratio; overall dimensions 280 X 185; single story (PNNL was 3 story) 33% window to wall ratio all 4 sides; window depth 4.29 ft 10 thermal block zones: 4 perimeter, 6 interior (this modification was made to accommodate more zones) Perimeter zone depth 20 ft Ventilation per ASHRAE 62.1-2013 of 5 cfm/pp, 0.06 cfm/sq ft Occupancy 200 sq ft /person office work using an office occupancy schedule (normal office hours) Overhead lighting 1.1 W/sq ft; Office lights/electric schedule and 0.98 W/sq ft for open office area Electrical equipment 0.75 W/sq ft; Office lights/electric schedule Building envelope walls/roof/window assembly ASHRAE 90.1-2013 compliant based on climate zone All HVAC systems ceiling supply ceiling return8www.carrier.com/commercial

Figure 2: System Comparison by ZoneHOUSTON OFFICE BLDG (Climate Zone 2A)LOS ANGELES OFFICE BLDG (Climate Zone 3B) 30,000 30,000 25,000 25,000 20,000 20,000 15,000 15,000Pumps-HRPumps-HRHea ngHea ngCooling 10,000Cooling 10,000FansFans 5,000 5,000 0 01. SAV RTUEUI 102.22. VAV RTUGAS HW RHEUI 103.93. VAV RTUELEC RHEUI 114.34. VRF5. WSHP Loopw Heat Recoveryw DOASw DOASClg/Htg ERVClg/Htg ERVEUI 110.9EUI 103.31. SAV RTUEUI 79.2 30,000 25,000 25,000 25,000 20,000 20,000 20,000Pumps-HRPumps-HRHea ngHea ngCoolingCoolingFansFans 10,000 10,0004. VRF5. WSHP Loopw Heat Recoveryw DOASw DOASClg/Htg ERVClg/Htg ERVEUI 94.1EUI 92.6 15,000Pumps-HRHea ngCooling 10,000Fans 5,000 5,000 0 03. VAV RTUELEC RHEUI 86.0CHICAGO OFFICE BLDG (Climate Zone 5A)PHILADELPHIAZone 4A)PHILADELPHIA OFFICEOFFICE BLDGBLDG (Climate(Climate Zone 4A) 30,000 30,000 15,000 15,0002. VAV RTUGAS HW RHEUI 83.1 5,0001. SAV RTU1.EUI 93.7SAV RTUEUI 93.72. VAV RTU2. VAVGASHWRTURHGASHW RHEUI 94.2EUI 94.23. VAV RTU3.ELECVAV RHRTUELEC RHEUI 121.8EUI 121.8 04. VRF5. WSHP Loop4. RecoveryVRF5. WSHPLoopw Heatw DOASw HeatRecovery Clg/Htgw DOASw DOAS ERVwDOASClg/Htg ERVClg/Htg ERVEUI 104.3Clg/Htg ERVEUI 104.3EUI 102.3EUI 102.31. SAV RTUEUI 96.392. VAV RTUGAS HW RHEUI 95.73. VAV RTUELEC RHEUI 136.14. VRFw Heat Recoveryw DOASClg/Htg ERVEUI 104.35. WSHP Loopw DOASClg/Htg ERVEUI 107.3www.carrier.com/commercial

AnalysisHouston, Climate Zone #2 — Heavy cooling climate with some heating Cooling costs reduced slightly (5%) by economizer Heating costs minimal Reasonable utility costs: electric—8.5 cents/kwh; gas rate— 6.95/MCFObservations: During long cooling season, System 1-3 (rooftops) benefit from airside economizer and VFD equippedsupply fans (SAV 1, VAV 2 and 3). System 3 is the same as System 2 except electric reheat coils result in higher coststhan a gas boiler. System 4 (VRF) benefits from the VFD (inverter) equipped compression but the fans on the DOAS andVRF fan coils are detriments. In addition, efficiency of System #4 is penalized by not having an economizer. System 5(WSHP DOAS) is penalized by constant speed compressors and constant volume fans. In addition, there is no economizeron WSHP. The loop pump energy is small portion but the pumps operate whenever cooling or heating is required.Los Angeles, Climate Zone #3 — Temperate climate suited for economizer Cooling costs reduced over 30% Heating costs minimal High electric rate—15.73 cents/kwh; gas rate— 8.04/MCFObservations: RTU Systems 1-3 minimize electric usage (cooling with economizer and VFD on fans). Not enough heatingrequired f

be required to select a VAV box. A VAV system is a powerful tool for balancing indoor air quality and energy reduction. It matches the reduction of cfm provided by a central supply, relating to reduced rpms that capture the power reduction from the fundamental Ideal F

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