Biasi 24S Boiler Problem

[Biggles]

Biasi 24S Combi Boiler

My son has just moved into his house which has a Biasi 24S boiler, 2002 vintage.

For the first few days he only had the hot water switched on and it seemed to work fine - plenty of really hot water.

Since then he has removed one of the radiators for decoration, then repressurised the system (to 1.2 bar cold). Now with the heating switched on, the boiler frequently fails to come on. When this happens, pressing the boiler reset button resolves the problem temporarily. He has to reset the boiler about once or twice a day.

The red lockout lamp does not come on and he says he can hear the pump running when the boiler fails to come on.

We've had a look at the fault finding section of the service manual but nothing really matches this set of symptoms - all of the fault conditions which are resolved by resetting the boiler cause the red fault light to come on. I guess it's just possible that the red fault light is broken!

What is the most common/likely cause of this symptom?

Thanks Biggles

[John Rumm]

Had he run the heating ok before the rad move?

So have you checked that the call for heat from the stat is actually getting to the boiler?

Does the boiler attempt to light (i.e. you hear the fan spin up, perhaps clicks from the igniter?)

Does it still produce hot water on demand ok?

Broken lights don't usually work so good ;-)

I think we need a bit more diagnostic info first.

[Biggles]

No but the hot water ran OK, now it doesn't, or rather the pump comes on but the boiler doesn't fire up.

Not exactly but as the pump comes on it suggests the call for heat is getting there.

My son says not, it doesn't appear to do anything, just starts the pump.

No, doesn't produce hot water or heating.

Fair comment, I'm 150 miles away and although he is a qualified Mechanical Engineer he has no experience of domestic heating systems.

It seems somewhat of a coincidence that the hot water has become faulty about the same time as he removed the radiator, but it may be unrelated.

I'm wondering whether a full service might sort it out - dirty sensors etc? Puzzled as to why resetting the boiler makes the system work OK for a while though.

[John Rumm]

The boiler will go through an ignition sequence with a number of proving steps. Running the pump will be one. But others like detecting adequate airflow from the fan, adequate primary system pressure etc will also need to be proved before it gets as far as attempting ignition. Even when it it will need to prove the flame, and then check the overheat stats etc.

The obvious one to check is there is enough primary system pressure...

[Andrew]

Full service on a 14 year old Biasi (probably bought in B&Q with unknown installation history) will probably result in much sucking of teeth and mumbling about a replacement.