shower from combi boiler

I live in the UK and I have a Medway Main water heater supplying all the taps in the house and a shower. The shower has a Thermix Mk2 shower valve and a Deneve water governer in the cold pipe between the water heater and the shower. After the shower has been running for about a minute the flames in the water heater will die down and then this is followed by a noise and vibration from the Thermix valve that sounds and feels as if a piston is moving violently inside it every few seconds and this eventually becomes a loud whine.
I would get a new mixer valve except that the problem may not be in the valve. Can anyone offer suggestions please. I cant find out who manufactured the Thermix so as to ask them.
Thanks Ron Etherington
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I don't live in the UK. But you mention a mixing valve and your water heater flame. The two should have nothing to do with one another. The flames are controlled by the thermostat on the water heater. The water temperature is regulated through a mixing valve.
The whining sound you mentioned sounds like you may have garbage in the mixing valve. The type I use can be take apart and cleaned. That's the cheapest fix if this particular brand allows you to take it apart. If it is installed with unions, even if you replace the whole valve, it's still a fairly cheap fix. If you were in the states I would advise you to be sure to use a "whole house" mixer and not accidentally install a "single use" mixer. I assume the same would apply in the UK.
good luck with it.
On Mon, 23 Feb 2004 07:27:29 GMT, snipped-for-privacy@ntlworld.com wrote:

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Normally, in the UK, a shower mixer is just for the shower. It is basically a thermostatic mixing valve with flow and temperature controls and an outlet for the shower hose.
Christian.
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On Mon, 23 Feb 2004 07:27:29 GMT, snipped-for-privacy@ntlworld.com wrote:

Thanks to Blackbeard and Chris for swift help. Unfortunately the mixer valve doesnt appear to allow for opening and cleaning and as said I cant find the maker (Thermix?).
Ron
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Many shower mixers, particularly not the flush type have water connections at the same standard spacing as a bath mixer tap. It is often just a simple straight swap for a new mixer.
i.e.
http://www.screwfix.com/app/sfd/cat/pro.jsp?ts 597&id!764
Obviously, you do need to check that the connections are standard, though.
Christian.
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