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Project Info COMPLETE Project Title Central Valley Research Homes: Phase 2_Radiant_ET_Report_Winter2018_Supplement Project Number ET13PGE1068 Investor Owned Utilities PG&E End-use HVAC Sector Residential Project Year(s) 2013 - 2018

For four years (2015 to 2018), one of the Central Valley Research Homes (CVRH) in Stockton, CA has been used to evaluate radiant ceiling panel systems in a residential application. The radiant ceiling panel systems tested consists of two brands of panels. In addition, four air-to-water heat pumps (AWHPs) and four radiant panel distribution configurations have been evaluated. A high-performance ducted heat pump system (referred to as the “Reference HP”) was also evaluated as a performance benchmark for the radiant systems.

Key objectives of the first phase of testing were to evaluate comfort performance, energy use, panel thermal performance, and develop “best practices” for AWHPs coupled with radiant ceiling panels ( The primary goals for phase 2 testing were to evaluate additional AWHPs and configurations, documenting the comfort performance and energy usage of each relative to previously evaluated systems (

This report is supplemental to the heating season findings of the Phase 2 report, evaluating two additional variable capacity AWHPs (VC-AWHPs) and comparing performance to previous heating seasons.

Key Findings

  1. Comfort comparisons between radiant and conventional systems:The buffer tank was removed, assuming the variable speed AWHPs could modulate capacity low enough to avoid short cycling during low load conditions. Due to controls limitations with the first VC-AWHP tested, this resulted in significant overheating of the upstairs rooms. These issues were somewhat resolved with the second tested AWHP, resulting in improved comfort over the Reference HP.
  2. Overall system performance comparisons between the radiant system and the Reference HP: Full load heating COP without a buffer tank was 24% higher than with a buffer tank. Measured full load COP of the VC-AWHPs was within 15% of rating.
  3. Energy comparison between radiant and Reference system configurations: Despite controls issues that caused overheating of the indoor space, the energy use of the first VC-AWHP without a buffer tank was nearly equivalent to the Reference HP.
Project Report Document
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