WATER SYSTEM SAFETY
DELABIE THERMOSTATIC TECHNOLOGY SHW
SCW
Temperature control No non-return valves Mixed water
Mixed opening control Mixing chamber
SMW By closing the control
The thermostatic cell therefore closes the SCW. There is no risk of cross-flow between the SHW and SCW.
enter the mixing chamber so that the pre-set maximum temperature is not exceeded – typically between 38 °C and 44 °C depending on the application. Maintenance staff can also override the temperature limiter to undertake thermal shocks, but the user is unable to override the limiter, avoiding accidental scalding in day-to-day use. But there is still a risk of scalding for those vulnerable cohorts identified earlier. So, what is the solution?
‘Next generation’ TMVs Interestingly, the solution lies with the very same failsafe technology that enables TMVs to provide anti-scalding safety. For conventional TMVs the closing mechanism is located upstream of the mixing chamber. When the mixer is turned on, hot and cold water flow into the mixing chamber, where the thermostatic cell regulates pressure and temperature imbalances in the incoming water prior to delivery. The reason that cross-flow occurs is that the mixing chamber is subject to static pressure. If there is a sudden imbalance in pressure – for example due to simultaneous toilet flushes (as above), the imbalance will cause the mixed water to seek the path of least resistance, or lowest pressure. To guard against this, NRVs are installed on the inlets to prevent the pressure imbalance forcing hot water into the cold water supply pipes. At least a decade prior to the French ban on NRVs, Delabie’s engineers developed sequential thermostatic technology, which ensures that the water flow is controlled upstream of the mixing chamber. This ensures that the mixing chamber is not subject to static pressure, so there can be no cross-flow due to pressure imbalances, eliminating the need for NRVs. The mixer opens with only cold water, and the hot water only begins to flow when the lever is in the vertical position and the thermostatic cell starts to blend the hot and cold, taking into account pressure and temperature variations in the system. The anti- scalding failsafe technology reacts immediately if there is a cold water supply failure, shutting off the hot water supply. Likewise, if the hot water supply fails, the cold shuts off too, meeting the TMV3 requirements for failsafe.
, the SHW is closed.
CONVENTIONAL THERMOSTATIC TECHNOLOGY SHW SCW
Temperature control Non-return valves Mixed water
Mixed opening control Mixing chamber
SMW
Sooner or later, the non-return valves are obstructed by impurities, causing cross-flow between the SHW and the SCW, responsible for bacterial development.
Delabie’s wall-mounted sequential TMTs also feature
an often-overlooked component that has revolutionised hygiene in healthcare settings. Designed to isolate the water supply in front of the IPS panel, the Stop/Check connector allows the mixer to be removed for cleaning, descaling, and maintenance, without the inconvenience of removing the panels. Furthermore, the ability to isolate the water supply means that a failsafe check takes place in seconds.
If we return to our earlier example, a conventional mixer requires 30 minutes per year to check the failsafe and NRVs. The Delabie sequential TMV has no NRVs, and the failsafe check takes 10 seconds per mixer, a total of 20 seconds per year. These Stop/Check connectors are available on Delabie’s wall-mounted sequential thermostatic mixers and showers, offering improved user safety for patients and healthcare professionals wherever there is a scalding and infection risk, all while reducing the burden for over-stretched maintenance teams.
Conclusion Once poster boys for anti-scalding safety, TMV mixers have fallen from grace. Increased infection risks and onerous maintenance regimes have seen Estates teams replace TMVs where the risk of scalding can be mitigated through mechanical means. However, next-generation thermostatic sequential technology offers a new solution when faced with the perennial challenge of balancing anti-scalding risks with Legionella infection risks. User safety is still guaranteed thanks to the familiar anti-scalding failsafe, but without arduous servicing and maintenance routines. Perhaps it’s time to let the next generation of thermostatic mixing valves show their mettle?
References 1 Health & Safety Executive: Legionnaire’s disease Technical guidance HSG274 Part 2, Published March 2024. https://
tinyurl.com/4y5yuzc5
2 Association française de normalisation (AFNOR), NF Médical (DT077), I June 2017.
Conventional TMT versus Delabie’s sequential thermostatic technology.
Carole Armstrong
Carole Armstrong is the Senior Marketing manager for Delabie UK. A graduate of both Cardiff University and Manchester College, she joined the company 15 years ago. Fluent in French, and responsible for numerous high- impact communication campaigns, she is responsible for media relations and events, delivering online and print content for the UK market. Delabie says it is ‘the European market-leader for tapware and sanitary accessories, providing innovative, hygienic, and sustainable solutions for the non-domestic market’.
October 2024 Health Estate Journal 81
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