Faulty thermostatic shower mixer

calmac · 16 Feb 2011

A local firm installed my shower mixer, it did not work long

The hot water comes off an oil fired Rayburn and there is plenty pressure.The plumber says that the water was too hot and has ruined the therostatic valve, I think that other people are bound to have similar hot water off a ombi boiler for example.
The water is cold all the time now, and when i turn the temperature up a bit it cuts the water off completely.
Grateful for any solutions
Cheers,
calmac

seco services · 16 Feb 2011

can you feel the hot pipe inlet to the mixer is it hot ?

Alastairm · 17 Feb 2011

Hi
I had a similar problem when I had installed a new shower with thermostatic mixer and a shower pump to improve the water pressure. I had a gravity DHW/ pumped CH at the time with a header tank in loft; hot water pressure was not that great hence the need for a pump. The thermostat on the tank was not regulating the temperature so the boiler was continuously heating the water when it was on. The shower would work fine for about 2 minutes and then would go cold. Turning mixer for more hot water only reduced the water flow ie no hot water comming through. Both hot and cold water were run through the pump to ensure water pressures were balanced. The pump was not cavitating, no trapped air, there was plenty of hot water in the cylinder (as bathroom sink tap still ran hot water) and came to the same conclusion that the hot water was too hot and overheating the termostat.
Solution - I replaced the thermostatic mixer with a manual one and it worked fine (once the right temp had been adjusted).
For other reasons, I recently updated the DHW tank to a pressurised one with the water temp appropriately controlled (tank thermostat at around 60 deg C, motorised valve and pump). Out of curiosity, I reinstalled the original thermostatic mixer (mains pressure hot and cold water) and it works perfect!
Cheers
Alastair

calmac · 18 Feb 2011

seco services said:
can you feel the hot pipe inlet to the mixer is it hot ?

Yes, the inlet to the mixer is hot.[/quote]

calmac · 18 Feb 2011

Alastairm said:
Hi
I had a similar problem when I had installed a new shower with thermostatic mixer and a shower pump to improve the water pressure. I had a gravity DHW/ pumped CH at the time with a header tank in loft; hot water pressure was not that great hence the need for a pump. The thermostat on the tank was not regulating the temperature so the boiler was continuously heating the water when it was on. The shower would work fine for about 2 minutes and then would go cold. Turning mixer for more hot water only reduced the water flow ie no hot water comming through. Both hot and cold water were run through the pump to ensure water pressures were balanced. The pump was not cavitating, no trapped air, there was plenty of hot water in the cylinder (as bathroom sink tap still ran hot water) and came to the same conclusion that the hot water was too hot and overheating the termostat.
Solution - I replaced the thermostatic mixer with a manual one and it worked fine (once the right temp had been adjusted).
For other reasons, I recently updated the DHW tank to a pressurised one with the water temp appropriately controlled (tank thermostat at around 60 deg C, motorised valve and pump). Out of curiosity, I reinstalled the original thermostatic mixer (mains pressure hot and cold water) and it works perfect!
Cheers
Alastair

I see where you are coming from, looks like a manual mixer will be the solution.Thanks

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Faulty thermostatic shower mixer

calmac

seco services

Alastairm

calmac

calmac

DIYnot Local

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