Equipment Sizing: Manuals J & S

Transcription

1 Equipment Sizing: Manuals J & S Massachusetts Energy Code Technical Support Program 1 Who Is Mass Save? Mass Save is an initiative sponsored by Massachusetts gas and electric utilities and energy efficiency service providers, including -The Berkshire Gas Company -Cape Light Compact -Columbia Gas of Massachusetts -Eversource Energy -Liberty Utilities -National Grid -Unitil The Sponsors of Mass Save work closely with the Massachusetts Department of Energy Resources to provide a wide range of services, incentives, trainings, and information promoting energy efficiency that help residents and businesses manage energy use and related costs. 2 1

2 Presented by: Performance Systems Development 3 Agenda Related Code Sections ACCA Design Process What are Manuals J & S Consequences of improper HVAC sizing Manual J Types of loads Software inputs Reviewing Manual J reports Manual S Design conditions Reviewing Manual S reports Software Tools Summary & Questions 5 2

3 Related Code Sections IECC 2015 Section R403.7 Heating and cooling equipment shall be: Sized in accordance with ACCA Manual S Based on building loads calculated in accordance with ACCA Manual J. 6 ACCA Design Process Who is ACCA? ACCA (Air Conditioning Contractors of America) is the association of HVAC (heating, ventilation, air conditioning, building performance) contractors. They write the standards for the design, maintenance, installation, testing, and performance of indoor environment systems. Provide contractor accreditation (ACCA Quality Assured Contractors) Software powered by ACCA 7 3

4 ACCA Design Process ACCA has developed an entire HVAC system design process Code references Manual J & S (IECC R403.7) Manual D (IRC M1601.1) 8 ACCA Resources Brochures for code officials and contractors 9 4

5 Why Manual J & S? Problems with rules of thumb Rules of thumb X tons/sq.ft., or X CFM per ton Will this work for a house Built in 1970? 2016? Code? ENERGY STAR? Zero Energy Ready? Passive House? 15% window-to-wall ratio? 25%? Facing west? Facing south? With air leakage 3.0 ACH50? 7.0 ACH50? With leaky ducts in an attic? Tight ducts 100% inside? 10 Why Manual J & S? Consequences of improper HVAC sizing Under-sizing (rare) leads to: Hot or cold occupants Oversizing leads to: Higher installed costs bigger equipment/ducts Lower equipment efficiency Poor humidity control/potential for mold growth Occupant discomfort Large temperature swings Temperature variation throughout house Premature equipment failure/service calls 11 5

6 MA Code Compliance Baseline Study Results Only 14% of the homes complied with Manual J heating requirements Only 4% of the homes complied with Manual J cooling requirements On average, system sizing is 2X the maximum Source: Massachusetts Single-Family Code Compliance Baseline Study: Volume 2 Final Report, NMR Group, Inc & Dorothy Conant, October 21, What is Manual J?, Types of loads in Manual J, Software inputs, Reviewing Manual J reports MANUAL J 13 6

7 Manual J and the IECC Code Section R403.7: Heating and Cooling system shall be sized In accordance with ACCA Manual S Based on building loads calculated in accordance with ACCA Manual J Or other approved heating and cooling calculation methodologies. IECC Chapter 6: ACCA Manual J Eighth Edition What is Manual J? Residential Load Calculations Outlines simple & accurate procedure to estimate heat loss and heat gain for residential structures Provides step-by-step instructions on how to perform these calculations Applicable to conventional buildings Passive solar homes, underground homes, spaces used as solariums, etc. are unconventional types of residential buildings Note: Passive solar homes Passive houses Not applicable for commercial, institutional or industrial buildings 15 7

8 Manual J Other Sections Basic principles Definitions Calculation tables Appendix Mobile Home load calculations Multi-zone systems Multi-family structures Energy consumption & operating cost (can be used to select heating and cooling equipment) Detailed infiltration estimates 16 Design Temperatures Indoor design temperature Target indoor air temperature for comfort and efficiency Outdoor design temperature Heating: The temperature above which the outside air is 99% of the time Cooling: The temperature below which the outside air stays 99% of the time Goal: Determine the BTUs (and blower CFM) required to maintain indoor design temperature under 99% of outdoor temperature conditions 17 8

9 Types of Loads Heating Design conditions IECC Section R302 interior design conditions Maximum indoor design temperature for heating: 72 F Outdoor design conditions are based on location: Outdoor Design Conditions for Heat Loss Calculations (Sample) Location Heating 99% Dry Bulb Boston 12 Framingham 6 Worcester 5 Dry bulb = ambient air temperature Wet bulb = saturation temperature due to evaporation 18 Types of Loads Cooling Design conditions IECC Section R302 interior design conditions Minimum indoor design temperature for cooling: 75 F Outdoor design conditions are based on location: Outdoor Design Conditions for Heat Gain Calculations (Sample) Location Dry bulb = ambient air temperature Wet bulb = saturation temperature due to evaporation Cooling 1% Dry Bulb Boston 87 Framingham 86 Worcester

10 Types of Loads (Heating season) Heat loss from a structure: Windows & doors Above-grade walls Below-grade walls Ceilings and roofs Floors & slabs Air leakage Ventilation Ducts and duct leakage 20 Types of Loads (Cooling season) Heat gain to a structure: Windows & doors Above-grade walls Below-grade walls Ceilings and roofs Floors & slabs Air leakage Ventilation Ducts and duct leakage People Appliances & lighting 21 10

11 Manual J Software 22 Manual J Input Verification ACCA Checklist 23 11

12 Manual J Input Verification ACCA Checklist Design temperatures Verify outdoor design temperatures match location E.g. Boston: Heating = 12 F Cooling = 87 F Verify indoor design temperatures match code Heating = 72 F Cooling = 75 F 24 Manual J Input Verification ACCA Checklist Windows, glass doors, and skylights Do U-factors and SHGCs match the plans? Are window areas roughly equal to plans? Are exposure directions (N, S, E, W) correct? 25 12

13 Manual J Input Verification ACCA Checklist Building envelope assemblies Do the R-values match the plans? Do the total areas match the plans? 26 Manual J Input Verification ACCA Checklist Infiltration and ventilation Envelope tightness Is the infiltration rate 3.0 ACH50 or tight? Above-grade volume Is the volume roughly equal to floor area times ceiling height? Include whole-house ventilation (not spot ventilation) rates 27 13

14 Manual J Input Verification ACCA Checklist Ducts Location Insulation R-value code maximum duct leakage rate or extremely sealed This Photo by Unknown Author is licensed under CC BY-SA 28 Manual J Input Verification ACCA Checklist Internal gains Occupants = No. bedrooms

15 Manual J Results 30 MANUAL S 31 15

16 What is Manual S? IECC R403.7: Heating and Cooling system shall be sized in accordance with ACCA Manual S IECC Chapter 6: ACCA Manual S Version What is Manual S? Based on Manual J load calculations Provides instructions on how to interpret performance data given by manufacturers Gives instructions on how to select equipment Sets limits on equipment sizing Not applicable for commercial, institutional or industrial buildings 33 16

17 Manual S Equipment sizing Equipment Heating equipment Cooling equipment Central AC Heat pump Sizing Limit 140 % of calculated heat loss (or next nominal size) 115% of calculated heat gain (or next nominal size) 125% of calculated heat gain (or next nominal size) Design air flow Equipment rated air flow (cfm) on medium speed +/- 15% of design air flow 34 Equipment Sizing Heating example 1. Manual J calculated heat loss = 50,918 Btu/h 2. Oversize limit is 140% of 50,918 or Maximum output = 1.4 x 50,918 = 71,285 Btu/h 3. Proposed furnace output = 52,000 Btu/h 4. Proposed furnace output < Maximum output 35 17

18 Equipment Sizing Cooling example 1. Manual J calculated heat gain = 27,543 Btu/h 2. Oversize limit is 115% of 27,543 or 1.15 x 27,543 = 31,674 Btu/h 3. Proposed AC output = 30,000 Btu/h 4. Proposed AC output < Maximum AC output 36 Equipment Sizing Blower flow 1. Design air flow from Manual J = 1,116 cfm 2. Acceptable air flow range = +/- 15% of 1,116 cfm 0.15 x 1,116 = 167 cfm 3. Acceptable range = 949 to 1,283 cfm 4. Selected blower cfm on medium speed = 1,000 cfm 5. Selected blower cfm is within this range 37 18

19 Documentation ACCA Plan Review Form 38 Summary No rules of thumb! Use software Powered by ACCA Ensure accuracy of Manual J inputs Design temperatures Component areas R-values and U-factors Orientation Infiltration Whole-house ventilation Ducts Internal loads Manual S oversizing limits 140% for heating 115% for cooling (125% for heat pumps) 39 19

20 Residential Plan Review Checklist 41 Energy Code Support Questions about the energy code? Energy Code Support Hotline: Energy Code Support

21 Energy Code Field Guides Field Guides for Code Officials and Builders/Trades at: SuccessWithEnergyCode.com 43 Residential New Construction Incentives for energy efficient building and renovating Low-Rise New Construction Performance Path based upon Electric and Fuel savings, plus a % adder as compared to MA baseline incentives up to $10,000 High-Rise New Construction and all Master Metered Natural Gas Incentives based upon modeling by Program Manager Incentives also offered for existing buildings. Visit for the details

22 Residential New Construction Incentives Blended Savings Approach (BSA) Details at: 45 Thanks! Massachusetts Energy Code Technical Support Program 46 22