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Andrew Smith
Andrew Smith, HVAC Technician
Category: HVAC
Satisfied Customers: 3757
Experience:  Heating and Controls engineer
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Baxi 100 He plus, Had been know to show as fired but burner

Customer Question

Baxi 100 He plus,

Had been know to show as fired but burner doesn't come on,but most of the time the boiler was ok,no lockouts etc.
I drained down the boiler and removed the dhw heat exchanger as it was clogged up and cleaned it and replaced it. There was some water spillage ,like a cup full and some got on the wiring and tripped the red. I sprayed this with wd40 and left it to dry out.
I then replaced the condense trap as it was badly blocked and turned on the boiler.
Boiler failed to stay ignited for more than a few seconds.
The spark electrode from pub was making a racket and although I'm sure no water had got on pcb I opted to change the pcb.
I fitted the pcb and boiler fired and was working fine for the remainder of the evening.
I was called back the next day as the boiler was in lockout and again wouldn't stay ignited for more than a few seconds.
I then discovered the wholesales had given me a pcb for a baxi solo 18he and they exchange it for correct pcb.
I fitted correct pcb and boiler fired up straight away when running hot water.
I switched off tap but the hws light and burner stayed on?
I switched off boiler to reset this.
I switched the boiler into winter mode with the external control off but boiler was still trying to fire up and this is the same with hws,no tap running boiler trying to fire.
Still boiler goes to lockout after trying to fire a few times.
Please help
Submitted: 4 years ago.
Category: HVAC
Expert:  Andrew Smith replied 4 years ago.

Andrew Smith :

Have you checked your hw flow switch - this could have been the problem all the time if firing when it shouldn't, the burner comes on and the boiler overheats and you get the red light?

JACUSTOMER-gfnknswn- : There was no faults showing before I cleaned the heat exchanger.
JACUSTOMER-gfnknswn- : when I put the 'wrong board' in it was working fine for the remainder of the evening,when I put the correct board in it fired up first time but wouldn't switch off. And since then fails to fire.
Andrew Smith :

Thanks for the rating - we can take the conversation further?????????????

JACUSTOMER-gfnknswn- : I didn't mean to rate anything,think my ipad froze.
JACUSTOMER-gfnknswn- : it just seems the boiler was working. Abit of water got on the wiring terminals and trip the houses rcd.
JACUSTOMER-gfnknswn- : i sprayed wd40 and left it for several hours and returned with the wrong pcb(unbeknown to me) and fitted it and boiler appeared to be working. Then I got the call saying it was locking out so I got the correct pcb and all it does now is go to lock out and when I shut a hot tap off it still shows as I'm opening it?
Andrew Smith :

Can you check the hot water flow switch for continuity and make sure it is not sticking, if not then disconnect it and see if the boiler still fires?