CH/HW not working: help

4 Jun 2004
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United Kingdom
Hi everyone,

I have a problem with my CH System -- I should add that I have very limited experience with CH systems but would like to have some idea of the problem before I call someone out.

My system consists of a boiler that heats both the CH and HW, a three-port valve, Grundfis Selectric (50hz) pump, room thermostat, HW cylinder, HW thermostat and Honeywell ST1000 timer.....

Last night, at around 8pm the CH reached the desired temp after a couple of hours, then the temp fell and, despite the room thermostat calling for heat, nothing else happened: the boiler didn't fire up and the pilot light wasn't on, but the timer was on. The pump was making a very low sound and I thought maybe the problem had something to do with the pump.

However, this morning the CH & HW has not come on at all, and l've noticed that the timer has not progressed to the on time: the clock is not ticking, so to speak. Advancing the timer does do something: the pump makes a low noise, the thermostat calls for heat and the pump makes the same low sound (the pump has a three-speed dial that sometimes if I increased it would seem to get the CH system going when it sounded like it was struggling) but the boiler does not fire up.

Is this two seperate problems? Boiler and timer? I moved into the house six-months ago and the system hasn't been serviced yet, which I think it probably needed to be flushed as the house is about 10 years old.

Any help would be greatly appreciated.
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Timer sounds dud, manually advancing it should bring things on.
What's the boiler?
multi meter ... time .. open the large white box and check inside .. with every hting on there should be power at the orange wire ? is this so . ?
Thanks, Chris R, I will check the name of the boiler tonight. Never used a multi meter beforer, 2face, so I might have to call in the Dad for that one

I've been told that resetting the boiler and the tank might help
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Boiler is a Potterton Pr1maF, not sure which model no.

UPDATE: Have reset the boiler and now the heating works but the thermostat is still not working. Might be able to get a multimeter on it first thing tomorrow morning, so will report then if possible.
With the thermostat not working, got up extra early to turn the heating on. Boiler fired up but rads didn't heat. It's like the pump is struggling to get water to the boiler or to pump it round the system. Changing the speed setting sometimes gets the system working, like there is a blockage that by altering the force eventually shifts it. Could this be air in the system or sediment? Hot water was fine.
COuld be all sorts - first, find the lever on the end of the 3 port valve. Put all the power to the system off, You should be able to feel a springy resistance when you move the lever.
Now put ch only (not hw) on. The lever should go sloppy. If not, valve isn't opening and needs attention/replacement.
If you latch/hook the lever in the "man" position your rads will warm up with the hw.
Chris R, have done that. Felt the springy resistance but what do you mean by 'sloppy. I turned the heating back on and it slipped back, is that what you mean? Thanks for all your help so far.

Definitely sounds like there is a blockage in the pump or even air.

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