Distribution Effectiveness and Impacts on Equipment Sizing for Residential Thermal Distribution Systems

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Journal Article



This report builds on and extends our previous efforts described in "Leakage Diagnostics, Sealant Longevity, Sizing and Technology Transfer in Residential Thermal Distribution Systems - CIEE Residential Thermal Distribution Systems Phase VI Final Report, December 1998". This report concentrates on a new area of work: the interaction between distribution system effectiveness and equipment sizing. This issue focuses on the ability of downsized equipment with a good distribution system to deliver the same cooling to conditioned space as a typical Heating, Ventilating and Air Conditioning (HVAC) system. The cooling of the conditioned space is evaluated by looking at the concept introduced in the previous phase of this study: "Tons At the Register" together with comfort issues, such as how quickly a house is cooled ("pulldown time"), and the distribution of cooling throughout the house.

The key outcomes of this study are:

  • This investigation yielded a new duct leakage test called DeltaQ.
  • The existing ASTM Standard (E1554) for measuring duct leakage has been rewritten and submitted to the ASTM standards review process.
  • A draft ASTM standard for longevity testing of duct sealants was developed. A draft was submitted to ASTM subcommittee E06.41 for balloting and comment. The comments on the draft resulted in changes to the test method and apparatus. A new test apparatus was constructed with funding from the Department of Energy (DOE).
  • Simulations of summer temperature pulldown time have shown that duct system improvements can be combined with equipment downsizing to save first cost, energy consumption, and peak power and still provide equivalent or superior comfort.
  • Air conditioner name plate capacity ratings alone are a poor indicator of how much cooling will actually be delivered to the conditioned space. Duct system efficiency can have as large an impact on performance as variations in Seasonal Energy Efficiency Ratio (SEER).
  • Installation of high SEER units can reduce energy consumption with no apparent drawbacks
  • Duct efficiency calculations are included in the Low-Rise Residential Alternative Calculation Method Approval Manual for 1998 Energy Efficiency Standards for Low-Rise Residential Buildings" (CEC (1999)).
  • Procedures for HVAC System Design and Installation (for Home Energy Raters) have been updated.
  • Field testing has shown that standard flowhoods can be poor for measuring residential register flows. Results from this study were used by the California Energy Commission (CEC) in the formation of the current Energy Efficiency Standards for Low-Rise Residential Buildings (CEC, (1998)), often referred to as Title 24.

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