had a weird fault today on a baxi

[buckley plumb]

baxi solo wm 40/4 bf

- balanced flue boiler similar workings to a back boiler. pilot would not stay on due to wind - replaced thermocouple while it was out for testing - pilot stayed on so fired up boiler and it run for 20 - 30 sec then flames went out then gas valve clicked off 1min later . got my u gauge from van and attached to burner pressure test point - fire boiler again and burner pressure is 13mb which is correct - watch as burner goes out burner pressure is still 13mb and gas still going to burner so its not the thermo or o heat stat as that does not trigger untill 1min after burner goes out .strip boiler and check flue thinking lack of air - flue seemed ok prodded wire through air intake part of balanced flue .put back togehter and all seems well. all i can think of is that there was snow in the air intake that combined with the unusual swirly winds .the flue was close to an internal corner and the fumes could have been forced back into the air duct but there did not seem to be any flame lift and flame pic was good - if it was gas valve burner pressure would have gone .decided to come home and open the leffe to forget about it

 

[mattyp]

Did you pt the boiler ?

 

[buckley plumb]

inlet gas pressure was 20mb

 

[buckley plumb]

if the gas valve regulator was playing up I would have expected to see the burner pressure fall when it went out but it did not . the other weird thing was there was no flame lift

 

[mattyp]

Pt - Performance test with telegan !!

 

[buckley plumb]

did not check that mate if it re occurs will do that first

 

[iain85]

First off make sure it has a STRONG clean pilot flame. If this is weak clean the pilot injector out and is likely to be the cause.

 

[buckley plumb]

First off make sure it has a STRONG clean pilot flame. If this is weak clean the pilot injector out and is likely to be the cause.

pilot was good it was not cutting out on thermocouple gas valve didi not click off until 1 min after flame went out - had call this morning another baxi wm solo same fault its the bloody snow setteling on the bottom part of the flue grating not allowing the balanced flue to work correctly

 

[Rob Sale]

I reckon the winding on the solenoid are on the way out or the're is a short on a cable. did you check resistance on gas valve? have you check the limit stats/over heat stats?

 

[buckley plumb]

over heat stat ok other wise it would drop gas valve instantly - over heat stat ok the pilot and main burner were going out yet there was still gas coming through tested with u gauge on burner test point constant 13mb even when flame out until a min after when thermo couple cut out gas valve

 

[gassafe]

Could it be debris or blockage in the burner injector, that would explain sudden gas cut off, but valve still open and putting out 13mbar...? I'm just guessing here tho

 

[mattyp]

Are you saying the main burner goes out and the pilot stays on ? Don't think you are ! I would double check the pilot again , it could be ok lit alone but when the main burner starts its starved off gas and lifts and the thermoelectric valve is slow to shut the main burner off

 

[REDSAW]

burner jet worn/oversized/

 

[buckley plumb]

Are you saying the main burner goes out and the pilot stays on ? Don't think you are ! I would double check the pilot again , it could be ok lit alone but when the main burner starts its starved off gas and lifts and the thermoelectric valve is slow to shut the main burner off

pilot and burner went off together and burner pressuer stayed at 14mb it did not click off on the solenoid gas still there for 120 sec at burner until thermocouple shut gas valve off.if the burner blocked or shut oiff the gas pressure would rise or fall it stayed at what it should be.had another one with similar problems which was snow blocking the flue but this one seemed quite clear .went back to it yesterday as it was blown out by the wind - the sparker is a bit week and customer was scared to press it as quick as me - it lit instantly and worked fine just think this occasion it was the wind .when it went out before the pilot and main burner went out flame seemed to die down on main burner and go out but still pumping gas in and out of burner at 13mb until thermocouple come into operation.i did strip and clean burner and jet and pilot on the 1st visit will keep my eye on this boiler out of intrest.

 

[Deleted member 44451]

i used to have problems with old back boilers where the main burner came on and pulled the pilot flame off the tcouple taking the main burner off . replacing the pilot injector usually solved the problem

 

[buckley plumb]

i used to have problems with old back boilers where the main burner came on and pulled the pilot flame off the tcouple taking the main burner off . replacing the pilot injector usually solved the problem

see what you mean but this went out before the gas valve shut off from the thermocouple -

 

[iain85]

Are you saying the main burner goes out and the pilot stays on ? Don't think you are ! I would double check the pilot again , it could be ok lit alone but when the main burner starts its starved off gas and lifts and the thermoelectric valve is slow to shut the main burner off

Exactly this

 

[stoker122]

Sounds like lack of combustion air but would expect to see the flames hunting before being extinguished.

 

[buckley plumb]

had same fault on other boiler cleared the flue of snow and that was ok this one the flue seemed clear I do think the chamber was lack of air due to wind and snow .

 

[gassafe]

I look forward to hearing the solution to this boiler

 

[iain85]

Sorted yet?

 

[buckley plumb]

yes was the snow that blocks the bottom of the balanced flue causing lack of air flow had a few more on same estate - also spoke to a mate who works in the area and he had 10 in 3 days same fault cleared snow and worked ok