Baxi 105e Flame Failure Only with Central Heating

[Ninja_1980]

Yesterday I fitted a new PCB on a Baxi 105e with a “fault on fan or flue” error. It was showing the tell tale signs of a PCB fault (i.e. fan only spinning for a fraction of a turn before cutting out). Once fitted, the hot water demand on the boiler works fine with the boiler firing up as it should and the water being nice a hot.

When the central heating is called (via an external thermostat) the boiler goes into a sequence of firing up, then cutting out and eventually a flame failure fault appears. Also, the built in timer to the boiler is making a noise (very fast ticking – note this no longer controls the boiler) and I can heard a running water sound.

Any ideas??

 

[gassafeengineer]

new boiler. i work for a large company and we cry when we come across a 105 or a 105e

 

[lee32]

is the running water sound the pump running

 

[Ninja_1980]

The water sounds a little more like a trickle. However, the pump does run.

Someone else suggested it could be the min setting on the gas valve???

 

[hedsa]

gassafeengineer are you having a laugh one of the easiest boilers to repair. opp its sounds like your burners pressures need checking /resetting need a gas safe engineer to do this .

 

[Ninja_1980]

OK, will get an engineer out ASAP as we're coming up to winter. Just a quick question....

If the min gas pressure is set incorrectly then why does the boiler work fine when there is a DHW demand???

Thanks

 

[rojaca]

CH initial fires on min burner pressure approx 2mbar. Just check that Flame rectification electrode (rhs) spark gap is 4mm with the tip directly above burner port.

 

[rojaca]

with regard to ninja's question. DHW starts on full gas rate and modulates down. Try popping one of leads off gas valve modureg to drop valve to min rate and see what happens whilst in DHW (but only if your GSR of course).

 

[baxpoti]

new boiler. i work for a large company and we cry when we come across a 105 or a 105e

So what exactly is a 105?

 

[rojaca]

baxpoti. Are you an engineer for the evil empire?

 

[Ninja_1980]

Hi baxipoti, I've seen your replies to loads of other questions in this forum. What do you make of this problem???

Could it be a faulty replacement PCB or the burner pressure????

 

[rojaca]

Am I casting pearls before swine? I consider myself snubbed

 

[Ninja_1980]

No, no rojaca. I just like to get lots of opinions so I don't get ripped off by the plumber. btw, anyone know of a gas safe engineer in the Surrey area???

 

[Ninja_1980]

Just had a shower and have noticed the house radiators are roasting hot. Could this be a clue. Could the diverter valve be stuck????

 

[baxpoti]

baxpoti. Are you an engineer for the evil empire?

Darth Vader himself.