ET22SWE0047 - Master Mixing Valve Field Study
The California Plumbing and Energy Codes do not mandate master mixing valves (MMV) for temperature control of domestic hot water (DHW) recirculation systems. Prior lab or field studies has not investigated the energy savings potential of MMV in recirculation systems. While some applications such as large multifamily buildings, elder care facilities and other applications may require the use of mixing valves for health and safety reasons, there are many applications where DHW recirculation systems have been installed without the use of MMV. The study will install high performance MMV, known as electronic or digital master mixing valves (DMMV) that are designed for use with operation of recirculation loops and handle the dynamic nature of variable flow water draws downstream at the point-of-use. They also may have additional monitoring, remote adjustment and other components and controls built in depending on the manufacturer and model. They are much more advanced than the conventional wax type thermostatic mechanical master mixing valve (MMMV) and various other thermostatic/mechanical types available on the market, many of which were not designed or rated for operation of variable water draw distribution systems with recirculation return loop. This project is a field study of DMMV installation in commercial gas-fired and electric HP-based DHW systems that do not have existing MMV. The five sites will include restaurants, supermarkets, cafeterias, office buildings, multifamily buildings, fitness/recreational centers, and laundry.
California Plumbing and Energy Codes do not mandate master mixing valves (MMV) for domestic hot water (DHW) recirculation systems, though they are commonly used in multifamily and elder care facilities. Research has shown that adding digital master mixing valves (DMMV) can reduce water heating energy use by 6.5% to 18% for multifamily buildings with heat pump systems.
This study evaluated the energy impacts of DMMV in five sites, including a restaurant, multifamily building, senior facility, clinic, and hotel, comparing performance with and without MMV. The research found an average energy savings of 4.5%, with results varying from 11.4% to -4.9%. While gas-fired systems showed savings, heat pump water heaters (HPWH) did not perform as expected due to set point sensitivity.
DMMV offers energy savings potential, but successful integration requires proper contractor training and quality control during installation. Non-energy benefits, like pathogen control and reduced runouts, further support DMMV use.
