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HVAC LOAD CALCULATIONSANDTHE ENERGY RATERRESNET 2008Dennis J StroerCALCS-PLUSVenice FloridaCALCS-PLUS
Billy-Bob’s ProfessionalHVAC Load CalculationSizing ChartTrim with care on black lines follow instructions belowCutoutCutout1.5 to 2 Ton2.5 to 3.5 TonStand on curb and look through sizing holesWhatever hole the house fits in is the size unit to useNOTE: For larger homes and/or for zoning use two or more holes.CALCS-PLUSCutout4 to 5 Ton
OR, Just do the oldstand-by!X SQ FT PER TONCALCS-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. Weuse 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 entrance doorof each apartment. The purpose is to see if there were anyextreme pressure differences. The Florida Building Code saysthere cannot be no more than 2.5 Pascals pressure differenceacross closed doors between spaces.CALCS-PLUS
Uncontrolled AirflowThe elevator lobby wasfound to be a -27.3Pascals with respect tothe apartments. Thismeans air in theelevator lobby is tryingto 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 about controlled airflow.CALCS-PLUS
Controlled AirflowOpen and closing windowsTable fanAir conditioning systems.CALCS-PLUS
Room AirflowDetermined by the estimated Heat Gain/Loss;Cooling or heating which ever has beenchosen to dominate the system design.HVAC Load calculations performed on aRoom x Room basis.Based on the Heat Loss/Gain through thebuilding envelope relative to each room.CALCS-PLUS
Room x Room LoadsIf the HVAC system is the backbone of thehouse as a system. The HVAC load calculationis the backbone of the HVAC systemRequired to determine supply CFM for eachroomRequired 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 affect everyaspect 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 pipe layoutand 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
Under 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 summerdesign condition occurs, properly sizedequipment will operate continuously oralmost continuously, both loads will beneutralized, and the occupants will becomfortable.CALCS-PLUS
BUT,Design Conditions Only Occur ForA Few Dozen Hours Per Season.CALCS-PLUS
Design ConditionsCALCS-PLUS
Load vs Outdoor TemperatureCALCS-PLUS
Using table 1 from ACCA Manual J forWest Palm Beach the summer outdoordry bulb temperature is 90ºCALCS-PLUS
At Peak Load Conditions, Sunny Day, the loadon a given building is 32,000 BTU/HCALCS-PLUS
50% of the time or more temperatures are moderate;look how the sensible load drops on a 90 cloudy day!9,000 BTU/HDifferenceHowever, theLatent Loaddoesn’t dropat all.CALCS-PLUS
On a 80 Sunny Day the load drops by11,000 BTU/HThe LatentLoad onlydrops by500 BTU/H21,000 BTU/HCould this be an Issue?CALCS-PLUS
Sensible load variation shows a differenceof 9000 BTUH while our latent difference isbarley 500 BTUHCALCS-PLUS
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
GuidelinesTake full credit for load factors anddiversity when estimating internal loads.Take full credit for diversity whenestimating the cooling load on centralequipment.CALCS-PLUS
ACCA Manual J CALCS-PLUSV8
A Computer Only ProcedureFrom “Addendum B” from ACCA Manual J CALCS-PLUS
Forms &WorksheetsCALCS-PLUS
Floor Plan Required.CALCS-PLUS
Room x Room EntryCALCS-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
GeneralInformationCALCS-PLUS
The Design TabThe Data that isautomaticallyfilled in comesfrom Table 1A inACCA Manual J 8thedition.Outdoor DesignConditions For theUnited States andCanada.CALCS-PLUS
Table 1ARHVAC weather data base comes directly fromACCA Manual J version 8 Table 1A & 1B(microclimates).CALCS-PLUS
Default Room DataSet up default data so you don’t have to do repetitive inputs.CALCS-PLUS
From the Floor PlanCALCS-PLUS
Room Entry Data13.5CALCS-PLUS
System InformationDesign ConditionsInfiltrationVentilationAirflowCALCS-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)
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
A Plug for MJ8The possibility for experiencing comfortproblems at part load conditions can beminimized by observing the guidelinesset forth in Manual J.The Manual J calculation should take fulladvantage of legitimate opportunities tominimize the size of the estimatedloads.CALCS-PLUS
Thank YouQuestions?CALCS-PLUS
HVAC LOAD CALCULATIONS AND THE ENERGY RATER Dennis J Stroer CALCS-PLUS Venice Florida RESNET 2008. CALCS-PLUS Billy-Bob's Professional HVAC Load Calculation . chosen to dominate the system design. HVAC Load calculations performed on a Room x Room basis. Based on the Heat Loss/Gain through the building envelope relative to each room. CALCS-PLUS
