Problem with Thermostatic Radiator Valve

I have just replaced a TRV with a new one because the old one was not working. It would allow the room and radiator to heat up, but then it would go cold and not come back on until I turned the thermostat up a bit more. The radiator would warm up but then it would go cold again and not come back on. The problem is that the new one is doing the same thing! The valve is mounted vertically and is quite near (2" away from) a surface mounted double socket. Could this have an effect on it's operation?
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They're entirely mechanical in operation. But even if they weren't, it would be a poor design that suffered from some form of induction at that distance from mains wiring.
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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Is there a room stat?

then this is what is determining when the rad is on or off.

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Errrrr that's what a TRV is supposed to do. It allows hot water to flow until it reches the set temperature, then it closes and the radiator goes cold until the *room* temperature falls below the set temperature, the TRV opens and the radiator gets warm again.
Was the room uncomfortably cold?
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On 21/12/2003 "PaulM" a wrote :

Just curious.....
I assume these TRV's are the thermostatically controlled valves which can be fitted on each radiator? I have thought to fit these in the past, but been put off by the thought of having to drain down the heating system to fit them. Is there a type which can be fitted in place of the existing valve control knob, without need to drain or disturb the system?
Regarding the above problem, suggest it might be something to do with a lack of proper air circulation around TRV.
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Harry (M1BYT) (Lap)
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No - the valve they use is of a different type to the gate or lockshield valves fitted. It's a sort of spring loaded type.
Draining down and re-filling shouldn't be too difficult, and it's a good opportunity to replace the inhibitor which should be done every few years.

The heat of the rad should force air circulation. If that stops because it's gone cold, the valve would open anyway. Might be worth putting the sensor head horizontal - I've just done this with my new ones. Can't really say if they're any better - I'd no real complaints before.
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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you can do it without draining down the whole system, using plugs on the outlet and vent pipe of the feed&expansion tank in the roof. Drayton make a set which look like giants' earplugs (for a ripoff price) or you can buy expansion plugs and speedfit end caps to do much the same. If you're just doing one or 2 rads it's less hassle than draining down the system, but if you're doing the whole lot it's probably no more or less hassle to drain down the system. In either case it's probably a good idea to remove and flush clean the rad(s) you're doing (see thread 'Cleaning out central heating system' now showing at a d-i-y newsgroup near you).
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On 21/12/2003 "John Stumbles" opined:-

Thanks for the explanation to both, on the method of fitting these devices.
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Harry (M1BYT) (Lap)
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Are you sure that the valve is fitted the correct way round - some only work on the inflow side of the radiator - fitting on the outflow side might create some problems with it opening.

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