Undemanded HW & CH

3 Jun 2004
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United Kingdom
Can someone help!!
My CH consists of a Baxi Bermuda 401 CH unit with back boiler, a Landis & Gyr RWB2.9 programmer and a Grundfos pump. The CH temperature is regulated by controllers on the radiators, I do not have a thermostat. My problem is that even with the CH and HW programmer switched off, the boiler can be heard to 'kick in' and the pump runs resulting in the pipes to the HW tank being very hot.
Any ideas?
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It sounds like you have an incorrectly wired system, you should fit a room stat and a tank stat to control the boiler. That will save you money on fuel in the end.
By the discription of your system you probably have motorised valve(s) as well. Problem is the microswitch in one of the valves is sticking and giving power back to pump and boiler when no demand from programmer. And if there is one fitted to HW side (some systems only had one on heating) this is passing and allowing pipes right up to tank to get hot.
Thanks for your ideas.
I do have two Honeywell valves in the system, is there any way I can check they are operating correctly? and do you know what the grey adjuster type thumbwheel on the side of the Grundfos pump is for?
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The grey wheel is a pump speed selector and is usually on 2or3. To check valves turn power off an follow flex from valves which contain L.N.E wires plus either an orange and grey or a black and white.Into the wiring centre. Leave the L.N.E alone and one valve at a time disconnect the other two what ever colour they are(making a note where they came from).Turn power back on and test to see which one being disconnected stops boiler coming on .this will tell you which is the faulty valve.
Give the HW motorised valve a whack with a screwdriver handle. You might hear it spring shut! With everything off both valves should should need identical pressure on the lever to move the valve to the MAN position. No pressure means it's stuck open.

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