C/H Boiler - The solution??

[Richard Faulkner]

Hi,

Some weeks ago I asked about my Jaguar Combi which kept giving overheat fault messages.

Anyway - having had 2 CORGI engineers look at it, on both occasions it worked fine, so they couldn't diagnose the fault, although one said that the pump could be binding, thus causing an intermittent overheat as the hot water isn't pumped away.

So... each time I turn it on or up, I listen to the pump with a screwdriver.

The overheat occurs immediately if the pump doesnt run when the boiler fires up, and there is no immediate overheat if the pump is running when it fires up. It always eventually gives the overheat fault code, but I cant be sitting there with a screwdriver in my ear 24/7, so I dont know if the pump is stopping before the overheat.

It is therefore my guess that either

1) The pump is knackered and needs replacing or;

2) something is intermittently sending a signal to the pump not to run - which doesnt solve the problem

Is 2 possible? or is 1 highly likely?

[Ed Sirett]

I think both are possible, although running pumps tend to keep running AFAIK which would make for (2).

Perhaps you could change the pump (which is not a huge expense) and see if that fixes the problem.

[Richard Faulkner]

How much should a pump + fitting be?

The Grundfoss pumps I have seen seem to be around £125+VAT or so, so I would guess supply & fit would be around £200??

[IMM]

You have ascertained that the burner fires and the pump does not run at times causing the overheat problem. You could have a multi-meter, mains tester screwdriver or a temporary light attached to the wires of the pump. If the pump does not run and say the bulb lights up, then it is most probably the pump. If no signal to run the pump, then something deeper and the pump is fine. The burner should never fire without the pump running.

[Christian McArdle]

You can get a pump from Screwfix for 35 quid and it is very simple to fit, assuming the pump valves work. You can test if the valves are working by attempting to turn them off.

However, if the pump is internal to the boiler, which is quite likely in a combi, you may find it is a custom built item available for 2000 quid only from the manufacturer.

Christian.

[IMM]

The pump heads are generally common items. You could buy a £25 pump and take off the pump head and replace with that.

[Christian McArdle]

That wouldn't have worked with my pump. It sounded like a washing machine full of marbles!

Christian.

[Andrew Gabriel]

A friend had a problem with his heating not managing to warm up the radiators although everything sounded like it was running OK. In despiration he replaced the pump, and much to his surprise this fixed the heating. Upon inspecting the old pump, it had no impeller blades left, all of them having broken off. He never did find where they went, but heating's been fine ever since...

[IMM]

Always best to install a strainer on the boilers return protecting the pump and boiler.

[N. Thornton]

Pump IIRC about £30 from wickes.

Regards, NT

[The Natural Philosopher]

They are currently blocking IMMs 'mocrobore' sludge pipes....:-)

[Christian McArdle]

You've just given me a horrible image in my head of IMM's sludge pipes. ;-)

Christian.

[IMM]

You have been in the pub all afternoon haven't you?

[The Natural Philosopher]

No, I went to the bank and the supermarket.

[IMM]

And drew out money and darted into the boozer.

[The Natural Philosopher]

Why on earth should I? I've got better drink here. Not that I have had any of it for a couple of days.

[IMM]

Sad bastard eh! Sit at home at the meths rather than socialise with proper people.

[The Natural Philosopher]

I don't need to drink to socialise, you sad peasant.

[IMM]

A demonstrable attitude of snotty uniness. Tony Blair should send 500 bulldozers right through those two pieces of slum.

[The Natural Philosopher]

Ah. Another pice of brilliant deductive reaosning

(i) IMM didn't go there (ii) peopel that go there are better than IMM (iii) they must therefore be slums (iv) if its implementation of greed, envy, jeaolousy and cowardice politics you want, Nu Laber will always see you right.