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krisj · Joined: 01 Mar 2003 Posts: 1 Location: nottingham

I have a conventional central heating system and when my central heating comes on and off the pump comes on and off fine, however with the hot water the pump comes on and even though the boiler goes out the pump stays on until the time clock goes off or until you turn the temperature down on the thermostat that is attached to the tank.

Can anyone tell me if this is normal, and if not what will be causing the problem.

Thanks

Chris

ChrisR · Posted: Sat Mar 01, 2003 7:53 pm Post subject:

No, it's wrong. (Some boiler will keep the pump running for a while after they turn off to dissipate the boiler's heat, but that isn't what you describe.)
I'm pretty sure it's a wiring error, possibly within a faulty motorised valve, which have small switches operated by moving bits of bent metal! Trying a new valve (head) would prove the point quickly.
If left as it is, the hot water cylinder will be cooled by the boiler (when it's cold) in the summer.

AGILE · Posted: Tue Mar 04, 2003 10:43 am Post subject: Re: pump question

This sounds like a simple thermostat setting problem.

If the boiler and pump are to be switched off when the hot water is up to temperature then the boiler output must be set to a higer temperature.

Typically the HW cylinder should be set to about 55 degrees which is a little too hot to keep your hand on. The boiler should be set to at least 65 degrees if it is to have a chance of letting the hot water reach its set temperature.

Radiators should usually be operated at between 60 ad 80 degrees, the lower the better if they can give enough heat output. 60 is just a bit too hot to keep your hand on and 80 is far too hot to keep your hand on.

In all probability its your hot water cylinder thermostat which needs to be turned down. Let us know the outcome.

Tony Glazier

ChrisR · Posted: Wed Mar 05, 2003 6:03 am Post subject:

Oops yes sorry I'd misread. Embarassed

The boiler will cycle on and off, with the pump running, until the water temperature gets to the set level. So what you're describing is correct behaviour. Boiler temp is just too low for the HW cylinder temp.