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HVAC LOAD CALCULATIONSANDTHE ENERGY RATERRESNET 2009Dennis J StroerCALCS-PLUSVenice FloridaCALCS-PLUS

OR, Just do the oldstand-by!X SQ FT PER TONCALCS-PLUS

BUBBA’S PROFESSIONAL HVAC LOAD CALCULATIONSIZING CHARTAIR CONDITIONING OR HEAT PUMPFROM DESIGN TO INSTALATIONTRIMCAREFULLY1.5 TO2-TONTRIMCAREFULLY2.5 TO3.5-TONTRIMCAREFULLY4 TO5-TONTRIM OUT VERY CAREFULLY ON DASHGED LINES, THEN FOLLOW INSTRUCTIONS BELOWStand on curb across from the home you are performing the calculation on. Look through thesizing holes locating the best match. For larger homes and or zoning use multiple Sizing Holes.CALCS-PLUS

HVAC Load Calculations.Why should an Energy Rater performHVAC Load Calculations?What is meant by a Room x Roomcalculation?Why use ACCA Manual J Version 8?MJ8 Sensitivities.How can an Energy Rater benefit?CALCS-PLUS

Energy Raters and Air FlowEnergy raters are already familiar with airflow.We use air flow as a tool to do energy ratings.CALCS-PLUS

Two types of Airflow.With respect to residential and commercialconstruction there are two kinds of airflow.Controlled and UncontrolledEnergy Raters use controlled airflow toestimate the amount of uncontrolled airflow.CALCS-PLUS

Uncontrolled AirflowPressure readings were taken across the closed entrancedoor of each apartment. The purpose is to see if therewere any extreme pressure differences. The FloridaBuilding Code says there cannot be no more than 2.5Pascals pressure difference across closed doors betweenspaces.CALCS-PLUS

Uncontrolled AirflowThe elevator lobbywas found to be a 27.3 Pascals withrespect to theapartments. Thismeans air in theelevator lobby istrying to go into theapartment.CALCS-PLUS

Uncontrolled AirflowLeaky buildingsLeaky Duct SystemsUnbalanced building pressures.CALCS-PLUS

Uncontrolled Airflow InfiltrationInfiltration influences how the building reacts in terms ofhealth, safety, durability, comfort, and energy efficiency. Can be estimated with a high degree of accuracy. Can be tested with a high degree of accuracy. Can be eliminated or controlled.CALCS-PLUS

Duct LeakageInfluences how the building reacts in terms of health,safety, durability, comfort, and energy efficiency. Can be estimated with a high degree of accuracy. Can be tested with a high degree of accuracy. Can be eliminated.CALCS-PLUS

As Energy Raters weunderstand uncontrolledairflow.So lets talk aboutcontrolled airflow.CALCS-PLUS

Controlled AirflowOpen and closing windowsTable fanAir conditioning systems.CALCS-PLUS

The Building is a SystemAir Conditioning is a Sub SystemAir Conditioning Conditions Air, duh!Air Conditioning Moves AirAir Conditioning Blows and SucksAir Conditioning Affects BuildingPressureAir Conditioning Makes the BuildingCome AliveCALCS-PLUS

Room AirflowRelating to Air Conditioning SystemsDetermined by the estimated HeatGain/Loss; Cooling or heating which everhas been chosen to dominate the systemdesign.HVAC Load calculations should beperformed on a Room x Room basis.Based on the Heat Loss/Gain through thebuilding envelope and internal gainsrelative to each room.CALCS-PLUS

Room x Room LoadsIf the HVAC system is the backbone of thehouse as a system. The HVAC loadcalculation is the backbone of the HVACsystemRequired to determine supply CFM foreach roomRequired to select Supply OutletsRequired to select Return InletsRequired to design a Duct SystemRequired to diagnose comfort problemsCALCS-PLUS

303.5.1.5 Manufacturer’s EquipmentPerformance Ratings (e.g., HSPF, SEER, AFUE)shall be corrected for local climate conditionsand mis-sizing of equipment. To determineequipment mis-sizing, the capacity of heatingand cooling vapor compression equipment shallbe calculated in accordance with ACCA Manual J,Eighth Edition, ASHRAE 2001 Handbook ofFundamentals, or an equivalent computationprocedure, using the following assumptions: .RecognizeThis?CALCS-PLUS

ACCA Manual JV8TheStandardin theIndustryCALCS-PLUS

Why Use MJ8The heating and cooling load estimates affectevery aspect of the system design procedure From system selection To equipment selection procedures To placement and selection of air distributionhardware To duct routing and airway sizing or pipelayout and sizingBecause of this the load calculation must be asaccurate as possibleCALCS-PLUS

Value of Manual JEliminate Under-sizing of Heating &Cooling EquipmentEliminate Over-sizing of Heating &Cooling EquipmentHumidity Control During the CoolingSeasonEliminate Comfort ProblemsCALCS-PLUS

Relating to CoolingUnder Sizing EquipmentThe obvious problem with undersizedequipment is that it will not maintain thedesired temperature. However, slightlyundersized cooling equipment (by a marginof 10% or less) may actually provide morecomfort at a lower cost.CALCS-PLUS

Oversized Equipment Causesshort-cyclesmarginalized temperature controlpockets of stagnate airdegrades humidity control during thecooling seasonrequires larger duct runsCALCS-PLUS

Oversized Equipment Causesincreases the installed costincreases the operating costincreases the demand on our utilitiesadds unnecessary stress on equipmentCALCS-PLUS

Humidity ControlThe Next SubdivisionMust be a Florida ThingCALCS-PLUS

Humidity Control During TheCooling SeasonSensible and latent cooling loads areimposed on buildings located in hothumid climates.When the summer design conditionoccurs, properly sized equipment willoperate continuously or almostcontinuously, both loads will beneutralized, and the occupants will becomfortable.CALCS-PLUS

BUT,Design Conditions Only Occur For AFew Dozen Hours Per Season.2/23/2009CALCS-PLUSPage 26

Design ConditionsCALCS-PLUS

Outdoor design conditions used to estimate heatingand cooling loads do not represent the most severeweather conditions experienced at a particularlocation.However, they do represent extremes that, onaverage, will not be exceeded for more than a fewdozen hours per season.This means that when heating and cooling loads arebased on Table 1, recommended design conditions,comfort and performance are optimized for thousandof hours per season.BAIHP28

Load estimating and equipment sizing concepts must beexplained to the builders and home owners because theydo not understand that installation and operating costincrease and long term comfort decreases when loadestimates are based on record-setting weather conditions(MJ8, A3-2)2/23/2009CALCS-PLUSPage 29

Using Table 1 from ACCA Manual J for West Palm Beach thesummer outdoor dry bulb temperature is 90º2/23/2009CALCS-PLUSPage 30

At peak load conditions, the HVAC loadcalculations shows the net gain on thebuilding is 32,000 BTUH total.2/23/2009CALCS-PLUSPage 31

50% of the time our temperatures range is in the moderate temperaturezone. The net gain could drop to 23,000 BTU/H on a 90 day if the sun isbehind the clouds.2/23/2009CALCS-PLUSPage 32

Sensible load variation shows a difference of 9000 BTUHwhile our latent load remains the same!7,500 BTUHNO CHANGE IN LATENT LOAD2/23/2009CALCS-PLUSPage 33

Lets say the temperature dropped to 85 when the sunwent behind the clouds.Sensible load drops to 16,500 BTU/H, a difference of 15,500BTUH.16,500 BTUH7,500 BTUH7,200 BTUHWhile our latent difference is barley 300 BTUH2/23/2009CALCS-PLUSPage 34

If your load calculation came out to 39,500 NET BTUH,what size system would you install?32,000 BTU/HSensible7,500 BTU/HLatent39,500 BTU/H NET BTUH , 81% SHR2/23/2009CALCS-PLUSPage 35

MJ8 SensitivitiesDesign conditionsBuilding tightnessFenestrationAir System Design & InstallationCALCS-PLUS

GuidelinesUse outdoor design conditionsrecommended by Table 1 Manual J.Use the default indoor design conditionsrecommended by Manual J.Take full credit for all internal shadingdevices and external overhangs.Use internal shading devices that arecompatible with the type of room.CALCS-PLUS

GuidelinesDo not use internal shade if the room isspecifically used for day lighting.Use the tested performance coefficients whenknown.Take full credit for all insulation & sealingefforts.Take full credit for insulated & sealed ductruns located in unconditioned space.CALCS-PLUS

ACCA Manual J CALCS-PLUSV8

A Computer Only ProcedureFrom “Addendum B” from ACCA Manual J CALCS-PLUS

From Part of Section 1-16ACCA Manual J 8th Edition Computerized method calculates load bymonth of year and time of day associatedwith each room load and with theequipment sizing load. Computer can generate solutions for 288scenarios (12 month year and 24 hour day) CALCS-PLUS

Forms &WorksheetsCALCS-PLUS

Only three software programs arerecognized by ACCA as meeting thestandards of Manual J residentialload calculations.CALCS-PLUSElite SoftwareRHVACWrightSoftRight-JNitekHVAC Wizard

CALCS-PLUS

Floor Plan Required.CALCS-PLUS

Room x Room EntryCALCS-PLUS

Room Entry Data13.5CALCS-PLUS

Table 1ARHVAC weather data base comes directly fromACCA Manual J version 8 Table 1A & 1B(microclimates).CALCS-PLUS

Outdoor Design ConditionsThe Data that isautomaticallyfilled in comesfrom Table 1A inACCA Manual J 8thedition.Outdoor DesignConditions For theUnited States andCanada.CALCS-PLUS

System InformationIndoor DesignConditionsInfiltrationVentilationCALCS-PLUS

MJ8 & Infiltration ForWinterCALCS-PLUS

MJ8 & Infiltration ForSummer Loose ConstructionCALCS-PLUS

MJ8 & Infiltration5,739 BTUH gainfrom a looselybuilt building bytoday's standardsCALCS-PLUS

MJ8 & Infiltration ForSummer Tight ConstructionCALCS-PLUS

MJ8 & Infiltration939 BTUH gainfrom a looselybuilt building bytoday's standardsCALCS-PLUS

InfiltrationSensitivityTIGHTLOOSELoose ConstructionTight ConstructionCALCS-PLUS

MJ8 & Duct LeakageCALCS-PLUS

MJ8 & Duct DesignDesign room CFM (airflow)CALCS-PLUS

Duct LoadsDucts located in the unconditionedspace also have a heat gain thatadds to the cooling load of thebuilding.CALCS-PLUS

Calculate Duct LoadsThe Sensible Loss, SensibleGain, and the Latent Gain arecalculated for the ductsystem.CALCS-PLUS

What If?Extremely sealed (sealshall be verified by leakage test)CALCS-PLUSAverage sealed system(MJ8 default)

REPORTSCALCS-PLUS

Envelope MaterialsPage 63CALCS-PLUS2/23/2009

Internal and Other GainsCheck FiguresNet ResultsPage 64CALCS-PLUS2/23/2009

Room LoadsCALCS-PLUS

BuildingRotationReportCALCS-PLUS

AED forWorse CaseOrientationFront Facing WestCALCS-PLUS

BuildingRotation ReportThe Building RotationReport calculates requiredcooling load for each ofeight directions along withthe required room CFM foreach room.This is very useful if thehome does not have AEDand it will be located in asubdivision and orientationis not known yet (worstcase direction).CALCS-PLUS

Our home has AED so the load does notchange much from when rotated.If the home does not have AED!CALCS-PLUS

Equipment SelectionMatching the MJ8 Results toManufacturer’s Performance Data2/23/2009CALCS-PLUSPage 70

1.92 Tons(Based OnSensible Latent2.12 Tons (Basedon 75% SensibleCapacity)?2/23/2009CALCS-PLUSPage 71

Manufacturers performancecooling data (like the one at theright) will give systemperformance at conditions otherthan ARIFor the area of the country thishome is going to be located wewill be interested in how thesystem will perform at or nearMJ8 design conditions of 91ºFoutdoor and 75ºF @ 50% RH.2/23/2009CALCS-PLUSPage 72

2/23/2009CALCS-PLUSPage 73

MJ8 & the Energy RaterThe information you gather to do aenergy rating is the same as requiredfor an HVAC Load Calculation.Do it to set yourself apart from yourcompetition.Do it to become a better Energy Rater.Do it to provide another avenue forincome.CALCS-PLUS

Larger Customer BaseAC Contractors know or at least had tohave learned load calculations if theycarry a licenses or certification.AC contractors are busy running acompany and don’t have time to doroom x room calculations.If they were provided room x roomcalculations they would use them as adesign tool.CALCS-PLUS

Diagnostic ToolStart every diagnostic investigationwith a room x room HVAC loadcalculation.You will understand the construction ofthe building much better.You will have a better understanding ofthe results of all the data gathered.CALCS-PLUS