On 09/11/2016 18:32, Biggles wrote:
On 09/11/2016 11:34, John Rumm wrote:
On 09/11/2016 01:30, Biggles wrote:
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.

Had he run the heating ok before the rad move?

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

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.

So have you checked that the call for heat from the stat is actually
getting to the boiler?
Not exactly but as the pump comes on it suggests the call for heat is
getting there.

Does the boiler attempt to light (i.e. you hear the fan spin up, perhaps
clicks from the igniter?)
My son says not, it doesn't appear to do anything, just starts the pump.

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.

Does it still produce hot water on demand ok?
No, doesn't produce hot water or heating.

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!

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

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

I think we need a bit more diagnostic info first.
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.

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

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.


--
Cheers,

John.

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