Water Heaters and Hot Water Distribution Systems

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This project conducted research to improve the efficiency of water heaters and hot water distribution systems in California. The three general areas were to develop:

  • standard change proposals for the 2008 Title-24 Building Energy Efficiency Standards;
  • a plan to successfully bring a super efficient gas water heating appliance to market;
  • a plan to assess the energy savings potential of improvements of Hot Water Distribution Systems (HWDS) in existing single-family residences.

This final report does not cover the research results of all the diverse tasks of this project in detail. Only the broadest, most general findings are discussed in this report. The full details of the individual tasks are covered in individual task reports attached to this final report.

Proposals were submitted to the Commission's standards office for changes in Title 24 to : modeling tankless water heaters to account for the impact of small hot water draws and heat exchanger "cool down"; the Distribution System Multiplier and eligibility requirements for various residential hot water distribution systems to accurately reflect their performance; the mandatory requirements for parallel piping hot water distribution systems to more explicitly define acceptable installation; and the analysis of energy efficiency measures that reduce consumption of hot water to include the cost of saved water.

Proposals for changes to the Uniform Plumbing Code (UPC) were submitted to the International Association of Plumbing and Mechanical Officials (IAPMO) to: distinguish between hot and cold water distribution systems, use the diversity factors for multiple bathrooms as the standard method of design, require all hot water piping be insulated, and require all buried water piping be installed in waterproof conduits.

The Super Efficient Gas Water Heating Appliance Initiative (SEGWHAI) was developed under a separate contract (500-05-010). This project provided support for SEGWHAI and modeled how efficient a replacement water heater could be without unconventional or condensing designs.

This project also included a literature review of previous HWDS studies, assessed available sensing and monitoring technologies, and added questions about hot water use to a water utility survey on household water use.

A total of fifteen reports describing the findings of the research undertaken for this project are attached.

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Prepared For: California Energy Commission, Public Interest Energy Research Program, CEC-500-2005-007


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