DIY Doctor

Thermstatic radiator valves malfunction

Postby fred1953 » Sun Nov 23, 2008 10:24 am

Recently had a new Vaillant boiler fitted but when first turned on the al thermostic valves allow hot water to pass through although closed down. The radiators nearer the boiler seem to be most affected. When the system has been running a while the problem goes away.
Not sure if this anything to do with the problem but water is being pushed out the overflow requiring the boiler to be topped up every 3 or 4 weeks.
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Simply Build It

Postby plumbbob » Sun Nov 23, 2008 11:58 pm

Not all thermostatic valves shut off entirely. Unless they have an "off" position they may allow a small flow in cold weather.

What pressure (assuming this is a sealed system) is it being run at?

One radiator (in the bathroom or where the room thermostat is) must be fitted with normal valves which must be left open. Flow should not cause venting by the pressure relief valve, just excessive pressure.
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