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Postby phil19 » Mon Mar 31, 2008 8:11 pm

Help, the hot water works ok but the central heating only comes on with the water tank thermostat set to 70 c plus.
The pump works - any ideas?

The radiators have their own thermostats and they have to be set to the highest setting to enable the radiators to get warm. On occasion the rads stay warm for a small amount of time - about 2 to 3 mintues then they go off.

It seems that balancing the heating thermostat and the rads get the heating to come on.

The valves 1 for hot water - was replaced 2 weeks ago, 1 for heating seem t o work because the pipes above and below get and stay warm.

it is a honeywell 8842.

can anyone suggest what could cause this?
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Postby ericmark » Tue Apr 01, 2008 7:48 am

You tell us very little. But with many central heating systems the room thermostat works the motorised valve which in turn works the boiler. Many motorised valves have a manual operating leaver. Always worth moving this and see if the heating then works. If so you may be able to latch it on. This would only be a temp fix if it works as you will get water with heating and heating with water but will keep it going until you can get someone out. There are many systems most follow one of the Honeywell plans really do need more to go further.

Postby sparx » Tue Apr 01, 2008 10:23 pm

Hi, it seems you may have a problem with the location of the room thermostat, wherever it is fitted it must obviously be away from any rads & the rads in that area must not have thermostatic valves fitted.
If you have 2 valves then effectively you have 2 independant control circuits,ie the programmer/dual time clock which calls for C.Htg. &/or H.Water at set times
Each thermostat controls its respective motorised valve when 'called' by the prog/timer, if 'stat senses a need for heat it opens its valve which makes an internal switch to send a signal to start pump & boiler.
Basic checks: with C.Heating only on at timer does pump/boiler operate?
With H.Water only on at timer does pump/boiler operate? ( both with 'stats turned up above normal).
If one system works ok but other doesn't then it can only be either duff thermostat, duff valve, or wiring fault, however you could spend a lot of time without correct test equipment and it should not cost much for a good heating engineer/electrician to carry out these checks for you,
regards SPARX
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