Validation of a Hot Water Distribution Model Using Laboratory and Field Data

Research output: NRELSubcontract Report


Characterizing the performance of hot water distribution systems is a critical step in developing best practice guidelines for the design and installation of high performance hot water systems. Developing and validating simulation models is critical to this effort, as well as collecting accurate input data to drive the models. In this project, the ARBI team validated the newly developed TRNSYSType 604 pipe model against both detailed laboratory and field distribution system performance data. Validation efforts indicate that the model performs very well in handling different pipe materials, insulation cases, and varying hot water load conditions. Limitations of the model include the complexity of setting up the input file and long simulation run times. In addition to completingvalidation activities, this project looked at recent field hot water studies to better understand use patterns and potential behavioral changes as homeowners convert from conventional storage water heaters to gas tankless units. Based on these datasets, we conclude that the current Energy Factor test procedure overestimates typical use and underestimates the number of hot water draws. This hasimplications for both equipment and distribution system performance. Gas tankless water heaters were found to impact how people use hot water, but the data does not necessarily suggest an increase in usage. Further study in hot water usage and patterns is needed to better define these characteristics in different climates and home vintages.
Original languageAmerican English
Number of pages50
StatePublished - 2013

Bibliographical note

Work performed by Alliance for Residential Building Innovation (ARBI), Davis, California

NREL Publication Number

  • NREL/SR-5500-58756

Other Report Number

  • DOE/GO-102013-3945


  • arbi
  • behavior
  • Building America
  • hot water distribution systems
  • hot water usage patterns
  • model validation
  • pipe insulation benefits
  • residential
  • residential buildings


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