Britony 80 Combi - Chaffoteaux & Maury pump over running

mrdoo72

Hi

Recently my boiler had a pretty bad leak and I had it repaired (3 way valve replaced, I think!!!).

As the weather has started to get colder I dececided to run the CH just to check it. The boiler runs fine and seems to heat up most of the house rads but I have noticed that once the heat is up to the temperature set on the thermostat the boiler stops heating as normal but then continues to pump, over running. Where as before it would cut out until it was needed again. All it seems to doing is pumping and nothing else, when it should have stopped.

Also it appears that two of the radiators downstairs aren't heating up very well. I've attempted to bleed them of any excess air but this doesn't seem to be the problem. Could it be that they are sludged up and how would i check?

Cheers

ormus

are the inlet pipes red hot?
(before the rad valve).

mrdoo72

I turned the boiler on tonight and ran it for a while and the same thing happened. the pressure guage dropped down to about 0.6 bar whilst it was doing this and when the heating stopped the pumped continued to run and the pressure stayed at 0.6.

squeekswhenwalking

pressure is a bit low at .6 bar, need to top up to about 1 to 1.5 bar. Second with heating on turn off all rads that are working to see if any air gets pushed through to the ineffective ones.

mrdoo72

Ta I'll give that a go. The pressure only drops when the CH runs. is that normal!!!

keystone

mrdoo72 wrote: »

Ta I'll give that a go. The pressure only drops when the CH runs. is that normal!!!

There is no point just topping it up. Pressure should be 1 - 1½ bar when cold, 2ish when hot. If pressure drops when CH is on and running you have a problem. Does pressure rise first to around 3 bar before it starts to fall?

1. Check the pressure relief valve discharge pipe (15mm copper) outside. Is water coming out of it when heating on?

2. Check your expansion vessel. It has a schrader valve like your car tyre. Open valve. If nothing comes out it needs repressurising, if water comes out then the diaphragm is stiffed.

Cheers

ziggyman99

The pump over-run is caused by the water throttle (hot water flow sensor). Edit:I meant DHW flow sensor. Easily proved by removing the lead from the sensor and the pump stops. I've repaired a few of these. They are fairly uncommon boilers and alot of engineers shy away as they are a little different. I went to one that had been condemned because of this fault. 10 minute fix.

karl-123

http://www.diynot.com/forums/viewtopic.php?t=192612


:j same problem here tatty bye...............

no actual pump overun on that boiler
its controlled via ch/dhw thermistors

and pcb rather than a seperate stat on pipework...........

good luck karl............

gas4you

Quite a few boilers have the pressure drop when the pump starts up. Doesn't mean you have a problem, but do make sure you top it up to about 1.5bar cold with no pump running.