2021 Uniform Solar, Hydronics, and Geothermal Code

2021 Uniform Solar, Hydronics, and Geothermal Code


2021 Uniform Solar, Hydronics and Geothermal Code

The Uniform Solar, Hydronics and Geothermal Code is a model code developed by IAPMO to govern the installation and inspection of solar hydronic, and geothermal energy systems as a means of promoting the public's health, safety and welfare.  Published previously as the Uniform Solar Energy Code, the 2021 edition adds significant provisions concerning hydronic and geothermal systems. USHGC was developed using the American National Standards Institute (ANSI)-accredited open consensus process.

Key provisions of the 2021 USHGC and changes from the 2018 edition include:

  • New requirements for additives and chemicals installed in hydronic systems

  • New requirements for terminal units installed with hydronic systems

  • New maximum allowable oxygen permeation rate for PEX and PE-RT tubing in hydronic systems

  • Additional material standards for hydronic and solar thermal system piping, tubing and fittings

  • New requirements for both water source and air source heat pumps

  • New solar thermal system piping and tubing insulation requirements

  • Additional expansion tank requirements including methods for calculating maximum volume of forced and diaphragm type tanks

  • New requirements for design and installation of geothermal energy systems including open-loop, closed-loop and direct-exchange (DX) systems

  • New applicable material standards for geothermal plastic ground source loop piping and fittings

  • New requirements for pressure relief and shutoff valves installed in geothermal energy systems

  • New requirements for geothermal system installation requirements such as trenching, markings, setbacks, testing, just to name a few.

  • New listing requirements for solar PV equipment

  • Updated solar photovoltaic (PV) provisions to correlate with the latest NFPA 70-2020

  • New Appendix D – (IAPMO IS 34) Installation Standard for Residential Solar Photovoltaic and Energy Storage Systems






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