Introduction To Commercial Building HVAC Systems And .
Introduction to CommercialBuilding HVAC Systems andEnergy Code RequirementsReid Hart, PE, Pacific Northwest National LaboratoryU.S. Department of Energy Building Energy Codes ProgramEnergy Codes Commentator Webinar SeriesAIA Provider #: I014 AIA Course #: BECPWS816ICC Provider Course #8875August 11, 2016PNNL-SA-120201
Course Description andLearning ObjectivesOverview of common commercial building Heating, Ventilating, andAir-conditioning (HVAC) systems as they relate to energy coderequirements. Learn about the most common HVAC systems andequipment, along with energy-related components and controls.Several important energy code requirements will be reviewed,including what to look for in the field or on plans.Learning Objectives:1. Identify common HVAC system types.2. Identify important HVAC controls, includingeconomizers.3. Name high impact energy code items related toHVAC equipment and controls.4. List the steps in verifying fan power calculations.Building Energy Codes Program2
OutlineHVAC system basicsBasic controls that save energyOutside air economizersReferences to energy codesections in this presentationare to the commercialprovisions of the2015 International EnergyConservation Code (IECC).Fan energy limitsComplex systems:Central plantSecondary HVAC systemsHigh energy impact complex controlsHydronic system controlsSimilar requirements mayexist in the 2012 IECC orASHRAE Standard 90.1-2013,but section numbers will bedifferent, and there will beslight variation inrequirements.HVAC high efficiency optionBuilding Energy Codes Program3
HVACSystemBasicsSource: https://en.wikipedia.org/wiki/Air handlerBuilding Energy Codes Program4
Basic Purpose of HVACAir-conditioning for thermal and humidity nSource: ASHRAE Fundamentals Handbook 2013VentilationIntroduction of required outside airInternational Mechanical Code (IMC)Chapter 4 : VentilationASHRAE Standard 62.1Filtration of recirculated airExhaust of undesirable air (toilet, kitchen, lab exhaust)Air movement in spaceSpace pressurizationControl infiltrationMakeup of exhausted airBuilding Energy Codes Program5
Heat Gain vs. Heat Loss (Winter)Heat GainsSolar thru windows/wallsSummer transfer/infiltrationInternalHeat LossAir Leaks (Infiltration)Transfer (conduction &radiant) throughElectric Use, LightingBody HeatWallsRoofsFloorWindowsDifference supplied byHeater orAir ConditionerBuilding Energy Codes Program6
Air ConditioningTwo general types of air conditioning (cooling)Refrigerant-based: refrigeration cycle moves heat from one space(indoors) to another (outdoors)Refrigerant evaporates and condenses continuously within cycleRefrigerant has a low boiling point, making it ideal for HVAC systemsSimilar to car AC systemNon-refrigerant: evaporative coolingSimple vs. Complex (no longer a code distinction in 2015 IECC)Simple systems often use direct expansion coils or heatDirectly use refrigerant to cool or heat airGas, oil or electricity in a furnace to heat airSimple systems usually serve one zone with direct controlComplex systems transfer heating and cooling to secondary unitsCooling: the refrigerant is in the chiller and chilled water goes to cooling coilsHeating: a boiler generates hot water or steam that is piped to heating coilsComplex systems usually serve multiple zonesBuilding Energy Codes Program7
System Capacity SizingVerify that cooling and heatingcapacity sizing (load calculations)have been completed (C403.2.1)Verify that equipment is notunreasonably over-sized (C403.2.2)Why?For simple constant volumeequipment, fan energy use will besignificantly higher because fans mustrun constantly to provide ventilationFor larger multiple-zone VAV systems,fan and reheat energy use will behigher because the turndown ofoversized zone boxes is limited.Source: RoadTrafficSigns.comBuilding Energy Codes Program8
VentilatingTwo types:Mechanical ventilationFans pull outside air into building for ventilationVentilation includes both outside air and recirculated airRequirements are available for minimum outside air, based on occupancy,floor area and number of occupants (See the International Mechanical Code(IMC) Chapter 4 or ASHRAE Standard 62.1)Natural ventilationNo fansBuilding Energy Codes Program9
Simple HVAC SystemsPackage UnitsThru-wall air conditionerPackage Terminal Air Conditioner (PTAC)Package Terminal Heat Pump (PTHP)UnitaryAir conditionerFurnaceHeat PumpsPackaged, split, mini-splitVariable refrigerant flow (VRF)Source: reptw092h3g 9000btu PTAC wall air conditioner heat pump.htmSource: https://en.wikipedia.org/wiki/Air handlerBuilding Energy Codes Program10
Packaged Rooftop Cooling UnitPackaged Unit (DX cooling) Outside Air VentilationDX (DirectExpansion)CoolingCoilAirFiltersMin OA(Outside )MixedAirRoomThermostatBuilding Energy Codes ProgramSupplyFanSA(SupplyAir) orDA(DischargeAir)11
Refrigeration cycleCompressor uses electric power toincrease pressure of refrigerantCondenser “cools” refrigerant,refrigerant changes from gas toliquid. Removes thermal energyfrom systemExpansion device lowers pressureEvaporator (cooling coil) “heats”refrigerant and cools air, refrigerantchanges back to gas. Adds thermalenergy to systemPower: compressor, condenser fan,furnace blower, furnace in heatingmodeBuilding Energy Codes Program12
Variable Refrigerant Flow (VRF)Could be single zone (mini-split)Or multiple zone (VRF System)Just a complex heat pump, serving multiple zonesSource: ochanges/heatpump/Building Energy Codes Program13
Things to Check in the Energy CodeEquipment EfficiencyTables in C403.2.3Separate tables for each typeDifferent efficiency ratingsHigher is generally betterFurnace: AFUE v. EtCooling: SEER vs. EER vs. IEER vs. COPHeat pump heating: HSPF vs. COPIf multiple requirements: must meet allEquipment Efficiency ImportanceMost equipment must meet manufacturing requirementsExceptions:Regional requirementsOld inventoryVariable Refrigerant Flow (VRF) system efficiency is not covered in 2015IECC, but is in ASHRAE Standard 90.1-2013Building Energy Codes Program14
Basic Controlsthat SaveEnergyBuilding Energy Codes Program15
Top of the ChartsMost impactful basic HVAC control measures*Snow and ice melt heater controlTemperature setback schedulingFull 5 degree thermostat deadbandEconomizer controlsAdditional impactful complex HVAC control measures Photo courtesy of Ken Baker, K energyFull 5 degree thermostat deadbandLimits on simultaneous heating and cooling (VAV reheat)VAV ventilation optimizationSupply air temperature & fan static reset controlsOther impactful HVAC measures*Exterior ductwork insulation (C403.2.9)Fan power within limitsProper equipment sizingSnow and icemelt heaterswill use a largeamount ofenergy if notproperly andautomaticallycontrolled!*Rosenberg, M., Hart, R., Athalye, R., Zhang, J., Wang, W., and Liu, B. (2016). “An Approach to Assessing Potential Energy CostSavings from Increased Energy Code Compliance in Commercial Buildings.” PNNL for al/technical reports/PNNL-24979.pdfBuilding Energy Codes Program16
Temperature Setback SchedulingSimple control systemsProgrammable thermostatsSeven different daily schedules/weekManual overrideOccupant sensor is an alternativeDDC (direct digital control) systemsCentral scheduling of all unitsOptimum start activatedSource: n-to-building-automation-system-bas.htmlBuilding Energy Codes ProgramEnergy Myth:Setback does not save energybecause it takes so long towarm up in the morningNot true:Savings can be 5%-20% ofHVAC energy Use17
Full 5 Degree Temperature DeadbandA most significant controlfeature is temperaturedeadbandIf heating is set at 70 F, thencooling should be 75 FShould be the found conditionduring an inspectionWhy?Source: ammable-thermostat/Simple systems can fight eachother in open office areasVAV systems have excessivereheat if settings are too tightEnergy Star recommendedfactory default setpoints of:Heating 70 FCooling 78 FSource: www.AutomatedLogic.comBuilding Energy Codes Program18
Outside AirEconomizersBuilding Energy Codes Program19
HVAC – Economizers “Free Cooling”Quantity of OSA: Meet Minimum Ventilation RequirementEconomizer Function: Flush out building heat with cool outside airEconomizerVentilation AirBuilding Energy Codes Program20
Packaged Rooftop Cooling UnitPackaged Unit (DX cooling) Outside Air VentilationDX (DirectExpansion)CoolingCoilAirFiltersMin OA(Outside )MixedAirRoomThermostatBuilding Energy Codes ProgramSupplyFanSA(SupplyAir) orDA(DischargeAir)21
Basic OSA Economizer Idea22Building Energy Codes Program22
Economizer ComponentsDampers (not shown)Damper MotorsMAT/DAT sensorsSolid State ControllerOAT/RAT sensorsDry bulbEnthalpyCode econo requirementsOSA ductwork large enoughRelief damper providedIntegratedOperates with compressorCoordinated with cooling(Honeywell shown, often basis of OEM brands, out there for 30 years)Building Energy Codes Program23
OSA Economizer Savings1600 Executive Pkwy.15 min data0:15 1:00 1:45 2:30 3:15 4:00 4:45 5:30 6:15 7:00 7:45 8:30 9:15 17:3018:1519:0019:4520:3021:1522:00Region of Savings12022:4523:30601005080406030kWhTemperature / % damper 04050607080910111213Building Energy Codes Program14151617181920212224
Economizer Savings – It’s in the Settings!High limit needed to turn off economizer when not beneficial!Fixed dry bulb cuts off above 75 F, 70 F, or 65 F—depending on CZDifferential dry bulb cuts off when OSA RADifferential DB no longer allowed in Climate Zones 1A, 2A, 3A, 4AFixed or differential enthalpy high limit adjusts for humidity of OSAEnthalpy requires a paired dry bulb high limit in event of sensor inaccuracyEconomizer savingsTheoretically 60%Low high limitsettings: 10%-20%“Premium economizer” Code economizerSettings correctRelief airIntegratedCheckout & FDDBuilding Energy Codes Program25
Economizer: Things to Check in the Energy CodeDamper and ductworkFull sized OSA damperRelief damper; powered orbarometricHigh limit or changeoversetting (C403.3.3.3)Proper setpoint a mystery tomost field techniciansSettings typically too low;reducing or eliminatingsavings (55 F vs. 75 F)High Limit Set pertable C403.3.1.1.3(2)for climate zoneSource: y.aspx?cat HonECC Catalog&category W7459&catpath 1.1.2.1.14Source: http://www.zipeconomizer.com/New 2015 IECC Fault Detection &Diagnostic (FDD) Requirements:(C403.2.4.7) Sensors; faults & setup.The controller above does not meetthe new m/products/Jade-Economizer26Building Energy Codes Program
Top of the ChartsMost impactful basic HVAC control measures*Snow and ice melt heater controlTemperature setback schedulingFull 5 degree thermostat deadbandEconomizer controlsAdditional impactful complex HVAC control measureshttp://www.rockwoolasia.com/products and solutions/Full 5 degree thermostat deadbandu/2011.construction/9794/HVAC/Internal duct linerLimits on simultaneous heating and cooling (VAV reheat)VAV ventilation optimizationDuctwork in attics oroutside the buildingSupply air temperature & fan static reset controls(exposed on the roof)Other impactful HVAC measures*requires moreExterior ductwork insulation (C403.2.9)insulation:Fan power within limitsR-8 in CZ 1-4R-12 in CZ 5-8Proper equipment sizing*Rosenberg, M., Hart, R., Athalye, R., Zhang, J., Wang, W., and Liu, B. (2016). “An Approach to Assessing Potential Energy CostSavings from Increased Energy Code Compliance in Commercial Buildings.” PNNL for al/technical reports/PNNL-24979.pdfBuilding Energy Codes Program27
Fan EnergyLimitsBuilding Energy Codes Program28
Losses occur for eachconversion of energyWire orEfficiency:80% Losses of20%Fan BeltLosses6%Air FlowOverall Fan System EfficiencyMultiple Conversions Multiple LossesFanEfficiency:70% Losses of30%Meter kWMotor Input kWMotor Shaft kWFan Shaft kWAir kW WorkLossesOverall system efficiency [5.0 kW work] / [9.65 kW in] 52%The energy code manages overalllarge fan efficiency by limitingnameplate motor hp or fan bhpper cfm of airflow supplied.Building Energy Codes Program29
Fan Power LimitHVAC systems with total fan motor nameplate hp 5hpEither meet nameplate horsepower or fan bhp (C403.2.12.1)Based on supply cfm with pressure adjustmentsBuilding Energy Codes Program30
COMcheck: Mechanical - Fan SystemsDetermines Fan Power Limitations compliance for each fan systemMotor nameplate HP and brake HPBrake HP includes pressure drop credits as applicableInclude all supply, return and exhaust fans in each systemMay have to allocate partial exhaust to each systemDo not need to enter duplicate systems repetitivelyBuilding Energy Codes Program31
Variable Speed DrivesReducing fan or pump speed savesenergy at partial flowFans in hydronic and multiple zonesystems must be variable flow (C403.4.1)Dx 65 MBH or more: 2-speedCHW ¼ HP: VSDSo most chilled water (CHW) fans musthave variable speed drivesFor example, 80% flow results in a 50%power reductionA variable speed drive should be evidentat the site or on the specificationsSource: https://en.wikipedia.org/wiki/Variable-frequency driveBuilding Energy Codes Program32
ComplexSystems:CentralPlantSource: cement-a-certain-godlike-remoteness.htmlBuilding Energy Codes Program33
Complex Building Energy Use - HVACCategories of HVAC systems:Central PlantBoilers, chillers, cooling towersA few pieces of large equipmentDistribution SystemsPumpsPipe and control valvesDuctwork, diffusers and registersSecondary & Zonal HVAC SystemsAir handlers, with coils & economizersFan coils, VAV boxesChillerSelected based on:Space temperature and humidity requirementsFirst cost, operating cost, and maintenance costSpatial constraintsRedundancyBuilding Energy Codes Program34
Heating and CoolingHeatingTypical fuels are electricity and natural gasEfficiency matters:Electricity is 100% efficientE.g., 1,000 W hair dryer heats the room by 1,000 WBut what’s the source efficiency? Coal-fired power plants are typically only 35%efficientA heat pump is much more efficient than resistance heat; typically :@ 47F: 330% or COP 3.3 / 17F: 225% or COP 2.25 / HSPF 6.8Natural gas typically is 80% efficientE.g., 100,000 Btu/h gas input to a furnace may yield 80,000 Btu/h of heatingA condensing boiler or furnace has higher efficiency; exceeding 90%CoolingCentral chillerWater cooled or air cooledWater cooled requires cooling tower or heat rejectionBuilding Energy Codes Program35
Central Plant: BoilersHot water or steam boilers are typicalHot water more common for smaller buildingsUsually natural gas, but sometimes electric or oilWater inlet and outletFlue gasGas pipe (yellow)Building Energy Codes Program36
Central Plant: ChillersChillers use electricity to removeheat from the chilled water loop(and thus the building)e.g., cool the chilledwater from 54ºF to 44ºFhttp://carriercca.com/product detail.cfm?ln en&product id 53&cat id 48&parent id sBuilding Energy Codes Program37
Central plant: Cooling towerRejects heat from the chiller (transfers it outdoors).e.g., cool the condenser water (water from thechiller) from 85ºF to 75ºF.Water-cooled chiller is more efficient than air-cooledchiller due to evaporative coolingBuilding Energy Codes Program38
Things to Check in the Energy CodeEquipment Efficiency2015 IECC Tables in C403.2.3Boiler efficiencyChiller efficiencyPath A or Path BMeet both Full Load & IPLVHeat rejection (tower) efficiencyAir-cooled ChillerSource: llers.htmlBuilding Energy Codes Program39
ComplexSystems:SecondaryHVACSystemsBuilding Energy Codes Program40
Complex Secondary HVAC systemsSimilar to residential and small commercial HVAC systems, but biggerWork to maintain comfort conditions in the spaceComplex systems may be more expensive, but are usually moreefficient than smaller / simpler systems (depends)Usually get heating and cooling energy from a central plant throughchilled water and heating water pumped throughout the buildingSome “packaged VAV systems” are unitary, but serve multiple zonesHeat recoverysection makes itmore efficient.Transfers energyfrom outgoing toincoming air‘Air handler’ hasfan and coolingcoil, just like insimpler systemsBuilding Energy Codes Program41
Secondary HVAC System Air handlersThe H, the V, the AC in one pieceof equipment.Uses air dampers, and chilled andheating water from the chiller andthe boiler to heat and cool the air.Also filters the air and draws inoutside air.Building Energy Codes Program42
Distribution: Heating Coils, Radiant HeatersHydronic distribution: Water or steam is heated by the boilers, thendelivered to secondary heating units throughout the buildingVarious types of heat exchangers:Heating coils in airstreamsAir handlers, fan coils (hotels)Radiant heatBaseboard heatersRadiant floor heatingMore about hydronic controls laterChilled water distribution is similar;CHW from chiller goes to cooling coilsthrough pipesDuctwork is used to distribute heatedor cooled air and return or exhaust airBuilding Energy Codes ProgramHot/cold water flowsthrough tubes, airflows across tubes.Heat transfer!43
VAV Multiple Zone System ConceptOne variable air volume (VAV) central air system serves several zonesThe air handling unit (AHU) maintains the desiredPrimary supply air temperature (SAT)Duct static pressure (SP) using a variable speed driveThe setpoints for both SAT & SP can be resetHas preheat capability and may subcool air to reduce humidityCoordinates the OSA economizer with the cooling coil to provide coolingEach zone has aVAV box or terminalunit that:Modulates air flowbased on coolingloadMaintains minimumairflow forventilation needsReheats air to meetheating tunities-top-fiveBuilding Energy Codes Program44
Multiple zone system example:VAV terminal unit (VAV Box)Air inlet (from air handler)Heating coilAir damperactuatorHeatingcoil controlvalveAir outlet, to zonesBuilding Energy Codes Program45
Tying it all TogetherBoilerCoolingTowerChillerA typical large building commercialHVAC system:Central plant:BoilerCooling TowerChillerAirhandlerVAV terminal unitDistributionPumpsPipesControl valvesSecondary SystemAir handlerVAV terminal unitsBuilding Energy Codes Program46
High EnergyImpactComplexControlsBuilding Energy Codes Program47
Warning! Controls can be complicated!Source: Bob Davis at Ecotope48Building Energy Codes Program
Top of the ChartsMost impactful basic HVAC control measures*Snow and ice melt heater controlTemperature setback schedulingFull 5 degree thermostat deadbandEconomizer controlsAdditional impactful complex HVAC control measuresFull 5 degree thermostat deadbandLimits on simultaneous heating and cooling (VAV reheat)VAV ventilation optimization (C403.4.4.6)Supply air temperature & fan static reset controlsOther impactful HVAC measures*Exterior ductwork insulation (C403.2.9)Fan power within limitsProper equipment sizing*Rosenberg, M., Hart, R., Athalye, R., Zhang, J., Wang, W., and Liu, B. (2016). “An Approach t
Mechanical ventilation . Fans pull outside air into building for ventilation Ventilation includes both outside air and recirculated air Requirements are available for minimum outside air, based on occupancy, floor area and number of occupants (See the International Mechanical Code (IMC) Chapter 4 or ASHRAE Standard 62.1) Natural ventilation
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3.4 HVAC 84 3.4.1 HVAC Equipment 84 3.4.2 Cooling Equipment 85 3.4.3 Recent HVAC Cooling Purchases 96 3.4.4 Heating Equipment 99 3.4.5 Heating System Fuels 106 3.4.6 Heating System Efficiency 109 3.4.7 Recent HVAC Heating Purchases 113 3.4.8 HVAC
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