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Welcome to thePMG Educational ProgramSponsored by:
An Overview on ACCA’s ResidentialHVAC System Design ProcessJohn D. SedineEngineered Heating & Cooling, Inc.Cedar Springs, MI
Presentation Overview:ACCA Manual J, Manual S, Manual D1. Provide a fundamental understanding on the basics of what it takes todo an accurate residential mechanical system design:2. Provide verification points and caveats Code officials: For the purpose of issuing a permit Quality control personnel: Checking consistency/accuracy3. Highlight relevant ACCA resources and opportunitiesDisclaimer: This is NOT a design course!
Designer’s ObjectiveTo design a mechanical system that can add (heating) orremove (cooling) heat energy at a rate (BTUs per hour) thatwill allow the home’s indoor environment to achieve thedesign conditions.This will keep occupants comfortable and safe and providefor energy-efficient operation.
Part 1 – Load Calculation
ACCA/ANSI 2 ManualJ - 2016 Standard required in:– 2015 IRC §M1401.3, and– 2015 IECC §R403.7 Comprised of two sections– Normative: 9 pages of text and 200pages of tabular information that arethe enforceable requirements– Informative: 390 pages of in depthdiscussion, documentation, andexamples Latest ANSI approval in Feb 2016
Load Calcs: Heat Gain / Heat LossSummer Heat flows INTO thehome– Sensible heat – dryheat (dry bulb;thermometer)– Latent heat – wetheat (wet bulb;humidity)Heat Gain so we needcoolingWinter Heat flows OUT of thehome– Sensible heat onlyHeat Loss so we needheatingHeat flow is a rate; the units are Btu/h.(Analogous to mph).
Manual J Load Design ConditionsTwo design conditions hence, two sets of peakloads.Heat Gain (summer)Heat Loss (winter)Outdoor Design Temp(Geographic-specific)Indoor Design Temp1% db condition99% db condition75 F70 F
Loads That Must Be Accounted For(as applicable to the specific home) Fenestration (windows, glass doors, skylights) Opaque panels (wood/metal doors, above & below gradewalls, partition walls, ceilings, floors) InfiltrationVentilationInternal (number of people and appliances)System (ducts and blower)
Basic Load EquationLoad U x A x ΔTU the heat transfer performance index(how well a material transfers heat; it’s the reciprocal of R-value)A the Area of the surface (window, wall, ceiling, etc.)ΔT the temperature difference across the surfaceLoad units are Btu/h
Designer Software OptionsSimple load calculation – MJ8AE (Abridged Edition) Dwelling must be 100% compatible with AE Checklist Can be done by hand or using ACCA MJ8speedsheetFull load calculation – Full MJ8 Can be done by hand, but extremely time consuming Usually use third party software1ACCA vets third party software for compliance with MJ8 procedures, those that pass received “Powered byManual J” recognition (see: http://www.acca.org/standards/approved-software)1
Manual J, Form J1ae (Block Load)
Load CalculationMin. Verification Points Location (City, State) Outdoor design temperatures and grains(Why deviating from MJ8 Tables 1A or 1B?) Indoor design temperatures (75 F db cooling,70 F db heating unless superseded bycode/regulation) Orientation matches actual home or plan Occupants number of bedrooms 1 Conditioned floor area home or plan Eave overhang depth and internal shading home or plan / default Number of skylights home or plan Sensible latent heat gain total heat gain
What to Watch Out For Some practitioners will try to fudge the numbers toget bigger loads: Change the design temperatures (outdoor and/or indoor)Design to the worst case scenario (e.g., very loose house)Add more occupants than ‘number of bedrooms plus 1’Calculate duct loads even when ducts in conditioned spaceNot include window overhangs and shadingPuff up internal loadsUse a factor of safetyThe above practices are not supported by ACCA.Manual J instructs practitioners to be thorough andreflect the ACTUAL conditions.
Part 2 - Equipment Selection
ANSI/ACCA 3 ManualS - 2014 Standard required in:– 2015 IRC §M1401.3, and– 2015 IECC §R403.7 Comprised of two sections:– Normative: 22 pages of enforceablerequirements– Informative: 270 pages of in-depthdiscussion, documentation, andexamples Latest ANSI approval in May 2014
Overview Equipment Selection Steps1. Start with sizing values MJ8 heating load: For furnaces and boilers MJ8 cooling load: For cooling-only and heat pumpunits2. Manual S provides sizing rules Sets upper and lower limits for equipment totalcapacity3. Designer must use OEM performance data Capacity values must be for operating conditions
Size Limits For Each Equipment Type
Heat Pump Sizing LimitsDesigner must heed thenotes for the tables.
AHRI RatingsA piece of equipment’s AHRI rating is evaluated for air at:80 F db / 67 F wb entering the indoor unit, and95 F db entering the outdoor unit.A standardized testing point for equipment capacity andefficiency, but inappropriate for use in equipment sizing andselection.No one wants an 80 F indoor environment in the summer!And not every location will have a 95 F outdoor designtemperature.
Equipment Sizing / SelectionMin. Verification PointsCooling EquipmentHeating Equipment Type Model Type Model Sensible Capacity Latent Capacity Total Capacity Total Output Capacity Auxiliary Heating Cap.Within loadsizing limits To be verified To be verifiedBlower Info CFM ESP CFM ESPEquipmentInformationCapacities satisfydesign conditions(at design conditions)
What to Watch Out For Some designers will: Seek (incorrectly) to use AHRI rated capacitiesinstead of OEM engineering performance data Not interpolating the OEM performance data forthe capacity at design conditions Misread / misapply OEM performance data tables(can be very confusing, and will come in different configurations) Round up to next size Push for equipment outside of the sizing limits
Part 3 – Duct System Design
ANSI/ACCA 1 ManualD - 2016 Standard required in:– 2015 IRC §M1601.1 and §M1602.2– 2015 IMC §603.2 Comprised of two sections– Normative: 43 pages of enforceablerequirements– Informative: 213 pages of in-depthdiscussion, documentation, andexamples Latest ANSI Approval in Oct 2016
Friction RateWorksheet
0.23 IWCTEL 120 FT80FtTEL 255 FT
.23 * 100FR --------------375FR 0.061IWC / 100 Ft
Friction Rate ChartOutside of the“wedge” maylead to velocityproblems
Finding Each Room Cfm𝑅𝑜𝑜𝑚 𝐶𝐹𝑀 Blower CFM 𝑀𝐽 𝑅𝑜𝑜𝑚 𝐿𝑜𝑎𝑑𝑀𝐽 𝑇𝑜𝑡𝑎𝑙 𝐿𝑜𝑎𝑑 (ℎ𝑡𝑔 𝑜𝑟 𝑐𝑙𝑔) One value for cooling and one value for heating The designer must use the larger of the two cfmvalues for sizing the duct runsReminder: Loads are in Btu/hr
Example Air handler delivers 1000 Cfm at 0.23IWC (net) Total heating load: 60,000 Btu/h Total cooling load: 48,000 Btu/h𝐵𝑙𝑜𝑤𝑒𝑟 𝐶𝐹𝑀 𝑥 𝑀𝐽 𝑅𝑜𝑜𝑚 𝐿𝑜𝑎𝑑𝑅𝑜𝑜𝑚 𝐶𝐹𝑀 𝑀𝐽 𝑇𝑜𝑡𝑎𝑙 𝐿𝑜𝑎𝑑 (ℎ𝑡𝑔 𝑜𝑟 𝑐𝑙𝑔)Room 1Room 2Room 3Blower Cfm 1000Total heating load 60,000 Btu/hTotal cooling load 48,000 Btu/hC - Btu/h H - Btu/hC - CfmH - sign Cfm100420500
FR & Cfm Duct Size &Velocity Using a duct slide rule, theCfm and calculated FR will:– Provide values for sizingthe ducts Round Rectangular– Provide an associatedvelocity in feet perminute (fpm)
Velocity Limit Compare the velocity (feet per minute, fpm) at thedesign cfm with the limits for turbulence /noise control If the velocity exceeds the limits, then use thecfm for the limit velocity – resulting in biggerdiameter ducts
Manual DMin. Verification PointsACCA recommended minimum: ESP from blower table at Design Airflow (CFM) Total Component Pressure Losses (CPL) Available static pressure (ASP ESP – CPL) Lengths: longest supply duct, longest return duct, TEL Determined Friction Rate Used Manual J room loads to determine Heating/CoolingCFMs Ensure maximum airflow velocity limits are not exceeded
What to Watch Out For Designers that ALWAYS use a FR of 0.10– It needs to be calculated every time for the specific ductsystem details Check the math– ASP ESP – CPL– FR (ASP x 100) / TEL– Spot check a few register CFMs Not using balancing hand dampers inthe runout branchesNot altering the design for a house planthat is rotated to the opposite street side
Part 4: ACCA-Available Resourceswww.acca.org/codes
Free FormACCA Design Review FormEverything you needto check on one form. Load calculation Equipmentselection Duct system designFree to download atwww.acca.org/codes
Free StandardsFree PDF Downloads on HVAC Quality Installation (ACCA 5 QI) QI Verification (ACCA 9 QIvp) Quality Maintenance (ACCA 4 QM) Quality Restoration (ACCA 6 QR) Whole House Evaluation (ACCA 12 QH) and moreFree to download at www.acca.org/quality
Free Training for Code Officials(and Others!)Three-part video training on Manuals J / D / S Approximately 45 minutes for each segmentA bit more detailed than this presentationFree! www.ACCA.org/codesCEUs available from ICC ACCA is an ICC Preferred Education ProviderSee: .2 CEU; Cost for the J / D / S test 60CEUs haveassociatedcosts.
ACCA Technical Reference Note“Computing Manual J Infiltration Load BasedUpon a Target Envelop Leakage Requirement”Shows how to convert a maximum codeallowable leakage limit (say, 3 or 5 ACH 50 per the ICC IECC)to:1. Manual J infiltration CFM value, and thento2. infiltration load contributions (Btuh) of: sensible heating, sensible cooling, and latent cooling.
Free ACCA Membershipfor ICC Code OfficesTo obtain ACCA member benefits for free,contact:Karla Price HiggsVice President, Member ServicesInternational Code CouncilKHiggs@iccsafe.org
Educational OfferingsQI Design [Load Calcs, Equipment Selection, Duct Design, etc.]Offered via: In-person training(3-day class) Online training(18 hours of videos, plusassessments) Offline DVDs5-year certificates provided forsuccessful passage of final examThese each haveassociatedcosts.
Educational: Technician Training& CertificationOn-line learning– Technician Field Practices for QualityInstallation– Home Evaluation and PerformanceImprovement– Friction Rate Primer and Duct DesignFundamentals– Duct Diagnostics & Repair– Etc.Convenient affordable ondemand training focused on qualityHVACR installation, maintenance,home performance, and more.These each haveassociatedcosts.
HVAC Primer, residentialBob’s HouseA case study forunderstanding the residentialHVAC design process asdescribed in the ACCAresidential design manuals.May bepurchased atwww.acca.org/store/
HVAC Primer, commercialMaria’s RestaurantA case study forunderstanding thecommercial HVAC designprocess as described in theACCA commercial designmanuals.May bepurchased atwww.acca.org/store/
Contact Information:John D. Sedine, PresidentEngineered Htg & Clg1321 17 Mile Rd NECedar Springs, MI 49319johns@engineeredhvac.com616.439.3311ACCA Contact:Glenn C. Hourahan, P.E.Sr. Vice PresidentACCA2800 S. Shirlington Road; Suite 300Arlington, VA 22206glenn.hourahan@acca.org
www.iccsafe.org/conference#ICCAC18
www.learn.iccsafe.orgLearning Center: X33821
1. Manual J infiltration CFM value, and then to 2. infiltration load contributions (Btuh) of: sensible heating, sensible cooling, and latent cooling. ACCA Technical Reference Note “Computing Manual J Infiltrat
