04 October 2022
Depending on the set water temperature, the element within the thermostatic mixing valve expands or contracts and changes the proportion of hot and cold water mixed in the valve.
If the cold water supply shuts off, the valve swiftly closes the hot water supply to prevent users from scalding themselves.
TMV2 valves operate the same way as TMV3 valves with a maximum temperature stop and temperature regulator that copes with high water supply conditions. However, the difference is this thermostatic mixing valve must conform to British Standards as specified in BS EN 1111 and BS EN 1287.
The NSF TMV2 approval Scheme provides an easy approval guide that refers to testing, pre-approval requirements, recommended maximum mixed water outlet temperatures, operating conditions, full and factored approval, and details about the information and maintenance documentation.
TMV2 mixing valves are used in domestic settings, small business premises, and commercial or public buildings. The maximum static water pressure can withstand up to 10 bar in line with BS EN 1111 and BS EN 1287 requirements. The high flow pressure for hot and cold applies to BS EN 1111 and must be between 0.5 and 5.0 bar, whereas the low flow pressure for hot and cold applies to BS EN 1287 and must be between 0.1 and 1.0 bar.
A TMV3 mixing valve is certified to comply with NHS requirements issued by the Department of Health in the Health Technical Memorandum 04-01: Supplement – Performance specification D 08: thermostatic mixing valves (healthcare premises), 2017 edition. A third party tests and approves TMV3 valves to ensure they conform to the construction, sampling, leaktightness, durability, designation, installation and operating instructions, commissioning and in-service tests requirements, marking, and performance.
TMV3 valves are a legal requirement for UK healthcare premises but are also suitable for washrooms in commercial developments such as office buildings and public environments.
These mixing valves have enhanced thermal performance features and a temperature stop that allow a quick response time to loss of water pressure or changes in water temperature. TMV3 valves can also cope with extreme supply conditions and work at a maximum static water pressure range of up to 10 bar. High flow pressure for hot and cold ranges from 1 – 5 bar, and low flow pressure ranges from 0.2 to 1 bar.
There is a misunderstanding that accessible washrooms in commercial buildings must incorporate TMV3 valves for taps and showers because there is a relationship between healthcare and accessibility. This is not true.
There is no connection between accessible washrooms in commercial buildings and healthcare environments, and the UK Department of Health does not require TMV3 valves to be installed in commercial accessible washrooms.
When designing accessible washrooms, Document Part M of the Building Regulations stipulates that these washrooms must comply with BS 8300 standards – BS 8300 standards refer to BS EN 1111 and BS EN 1287. Thus, TMV2 valves conform to the relevant building regulations within the washroom environment and are acceptable for installation in commercial accessible washrooms.
