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Clarifying Eligibility for Residential Central System Heat Pump UES Measures: Single- and Two-speed outdoor units only. Regional Technical Forum April 17, 2012. Background.
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Clarifying Eligibility for Residential Central System Heat Pump UES Measures: Single- and Two-speed outdoor units only Regional Technical Forum April 17, 2012
Background • A new type of central heat pump system is now available with variable speed compressors; the question has been raised whether the RTF heat pump UES measures applies to these units. • Central System Heat Pumps with Variable Speed Compressors • Able to modulate capacity to more closely match heat load of house (similar to DHP, but with ducts) • Longer run times • Higher HSPF ratings
Applicability of Variable Speed Units to RTF Heat Pump UES Measures • Primary Issue: Duct System Interaction Unknown • Running the duct system for longer periods of time could have a significant energy penalty. (Note: HSPF ratings do not take this into account) • Also: PTCS Commissioning UES Specifications Undefined • Airflow testing requirements might not apply to systems with a variable-speed compressor. • Charge-checking is more complicated and it is unclear if QA agents would be able to do follow-up testing on these systems. • The data and analyses used for the UES measure apply to systems using single-speed (and to some extent, two-speed) compressors. • The 2005 Heat Pump Study did not include systems with variable-speed compressors • The SEEM runs use system performance curves and operating characteristics (on/off) of systems using single-speed compressors
Proposed Solution • Clarify eligibility requirements for existing heat pump measures • Additional eligibility statement in “Application” field: • Applies to systems with single-speed or two-speed compressors. • Applicable UES Measures (Residential - Heating/Cooling ) • Air Source Heat Pump Conversions MH & SF • Heat Pump Upgrades MH & SF • PTCS Commissioning, Controls, & Sizing MH & SF • As more data become available on the overall system efficiencies (including the duct system impacts), the RTF can look into UES measures for variable speed central system heat pumps. • Decision?