Thermostatic mixer showers with instant water heaters

by **clare hughes** » Thu Feb 25, 2010 5:39 pm

:?:
Can anyone help me here please - I have purchased an electric 12kw instantaneous water heater that is suitable for 2 outlets - a basin and a shower. I want to purchase a contemporary mixer shower to use with it, but have been told that I shouldn't use a thermostatic mixer shower with it.
Does anyone know the reason why?
And if I can't use a thermostatic mixer, is it ok to use a manual mixer shower? Cheers, Clare.

by **jnr plumber** » Mon Mar 01, 2010 3:50 pm

https://www.diydoctor.org.uk/projects/ch ... shower.htm

follow this link & click on mixer showers at the top.
hope this helps.

By utilising the instantaneous water heater which has two feeds (basin & shower) you risk the chance of scolding if for example the basin cold water was being used while somebody is using the mixer shower.
The drop in cold water will mean that the hot water will no longer be comfortable.

Even thermostatic showers may cut out if this scenario is in place.

by **clare hughes** » Mon Mar 01, 2010 4:25 pm

[quote="clare hughes"]:?:
Can anyone help me here please - I have purchased an electric 12kw instantaneous water heater that is suitable for 2 outlets - a basin and a shower. I want to purchase a contemporary mixer shower to use with it, but have been told that I shouldn't use a thermostatic mixer shower with it.
Does anyone know the reason why?
And if I can't use a thermostatic mixer, is it ok to use a manual mixer shower? Cheers, Clare.[/quote]

update 1/3/10
I was notified today that I had a reply, but I cant find it. When I click on my topic just my question appears.
Thanks to the kind person who replied, but could you please re-send your reply, and hopefully it will come through on a 2nd attempt. Thanks

by **jnr plumber** » Fri Mar 05, 2010 4:25 pm

https://www.diydoctor.org.uk/projects/ch ... shower.htm

follow this link & click on mixer showers at the top.
hope this helps.

By utilising the instantaneous water heater which has two feeds (basin & shower) you risk the chance of scolding if for example the basin cold water was being used while somebody is using the mixer shower.
The drop in cold water will mean that the hot water will no longer be comfortable.

Even thermostatic showers may cut out if this scenario is in place.

by **plumbbob** » Sat Mar 06, 2010 6:26 pm

All posts are moderated before appearing. This means there is a delay before they appear. You have to be patient.

I don't understand why you cannot use a thermostatic mixer shower with this type of heater. I am not saying you can, I would suggest you phone the manufacturer and ask what they recommend.

In fact, it is now a legal requirement for all bath and shower outlets in new building to have thermostatic blenders installed so the water cannot rise above 60 degrees so technically, any heater that cannot work with thermostatically controlled valves may not be legally used.

by **htg engineer** » Sat Mar 06, 2010 7:06 pm

Thermostatic showers are designed so that you cannot be scalded, so you would use a thermostatic mixer with the instantaneous water heater, set so that the maximum temp, is not too hot.

You would NOT use a standard mixer shower on this system.

You will probably need an expansion vessel on the water supply to take up expansion to prevent damage to pipes and water heater

htg