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TAG rejects mandated HVAC capacity check; proponents urged to refine proposal
Summary
A proposal requiring a field capacity check on ducted HVAC systems (O9) was disapproved by the TAG following discussion about test methods, climate applicability, sampling and the practicalities of applying a 10% tolerance.
Jonathan introduced proposal O9, a requirement to perform a capacity check on centrally ducted heating systems at installation time (a test referenced to the ANSI/RESNET/ICC commissioning standard task for measuring delivered capacity). The proposed test calculates delivered heat as CFM x 1.08 x measured —9Delta-T—9 (supply minus return) to verify the installed heat output is within 10% of the Manual J design.
Members raised multiple technical questions: how to test ductless systems (mini-splits), whether the test measured unit-only output or system-delivered heat (duct losses), and whether a single-device test could be applied consistently across different climates and seasons. Speaker Larry Andrews and others said measured output varies strongly with outdoor temperature and refrigerant behavior, and some cautioned that test conditions in summer may not reflect winter heating performance.
After extended discussion, the TAG moved to disapprove the proposal. The motion to disapprove carried (motion outcome recorded as carried in the transcript; recorded vote: 8 yes, 1 no, 8 abstentions). Several members suggested the idea could be reintroduced after a work group developed clearer test procedures, sampling protocols for multifamily projects, and clarified applicability (ducted systems only, test timing, and allowed instrumentation).
