Combi CH not performing

beggleston · 2 Mar 2004

I have vaillant Combi boiler and ever since we have moved in it has never managed to heat the room with the thermostat in to above 16/17 degrees c, or the rest of the flat for that matter. That is to say that after a period of time (reaching about 80 degrees c on the boiler thermometer) the boiler gives a status of \\\"pump over-run\\\" and the boiler temporarily stops until the internal temperature of the boiler has reduced to a suitable level. It will then fire up again and hit 80 degrees C before shutting off again - the cycle continues. In essence i think it is reaching max temperature internally without really moving the heat to the radiators. I have checked the pump speed, bleed the system etc. but still no joy. It is a relatively new system - about 4 years old i think. Any suggestions? getting annoying now.

ChrisR · 2 Mar 2004

Dud pump , sludge, obstruction, airlock,....
Hows the tap HW?

beggleston · 2 Mar 2004

HW is absoutely fine and powers our shower perfectly.

If the HW is fine does that rule out a problem with the pump? is it more likely to be an issue with the pipework of the CH sytem in that case.

essexjan · 18 Apr 2004

beggleston said:

I have vaillant Combi boiler and ever since we have moved in it has never managed to heat the room with the thermostat in to above 16/17 degrees c, or the rest of the flat for that matter. That is to say that after a period of time (reaching about 80 degrees c on the boiler thermometer) the boiler gives a status of \\\"pump over-run\\\" and the boiler temporarily stops until the internal temperature of the boiler has reduced to a suitable level. It will then fire up again and hit 80 degrees C before shutting off again - the cycle continues.

Click to expand...

I'm having exactly the same trouble with my boiler. Any ideas? Hot water is fine.

denny777 · 18 Apr 2004

sounds very much like the pump,but please tell me how hot do the Rads get,If at all

DP · 18 Apr 2004

Very much doubt that the pump is jiggered.

essexjan · 19 Apr 2004

sounds very much like the pump,but please tell me how hot do the Rads get,If at all

The rads don't get hot because the boiler cuts out after no more than 30 seconds. The temperature guage in the boiler climbs to 70C very quickly and then the boiler cuts out, and the error code is S7, which is 'pump over run'. There's nothing in the manual to explain what this means.

It's not the pump malfunctioning because the hot water is working just fine, and on a combi boiler, there'd be no hot water if the pump was kaput.

denny777 · 19 Apr 2004

Has the pump got a removable screw at the front of it,is so remove it and run the boiler,you should be able (with the use of a screw driver to feel the impellor on the pump spining,if it is the pump must be ok,

breezer · 20 Apr 2004

essexjan said:
It's not the pump malfunctioning because the hot water is working just fine, and on a combi boiler, there'd be no hot water if the pump was kaput.

I hate to tell you this, but that is not right (not in our case) we had probs with heating (i did post on here, also result) hot water was fine, turned out the pump was Kuput (impellar all smashed up, i saw it)

BG man said that hot water comes out under pressure from supply, pump is there only for heating

fathertobe · 29 Mar 2006

Was there ever a clear resoultion to this problem? I think I have the same issue - except that my rads actually do get hot (before the CH shuts off)...

chrishutt · 30 Mar 2006

Father Tobe, you shouldn't dredge up old threads! You've already got a thread running on your "problem" - getting people to post here as well will just confuse the issue.

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Combi CH not performing

breezer

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