baxi solo 3 50 pf overheating

[bewsh]

How's it going guys? Just want to pick your brains. My mate went to a baxi solo 3 50pf because the fan had failed, he replaced the fan and it was working fine, now they say that since the fan has been changed the boiler keeps overheating. So I went over today to have a look thinking it was probably the pcb pump overrun. But after looking at it, when you turn the c/h on the mid pos moves fine, but you knock it off and you still get 210vac on the orange to the boilers s/l and the boiler stays on. I tested all the controls, room stat, programmer, cylinder stat and they all proved to be ok, so thought it must be a faulty mid pos giving power to the orange with no demand. But am I right in thinking that of it's still giving power to the boiler, then the pump should also continue running? Cheers guys

 

[Ermintrude]

Pump should still be running but against a dead head?

 

[bewsh]

That's what I thought, but the pump stops after a few minutes and the valve is still open to c/h, so continues pumping when you turn the demand off, but then goes off and then overheard because the boiler is still lit. So possible pcb issue also?

 

[moogwai]

Micro switch in mid pos valve aint sticking is it? Something is keeping the orange live to keep the boiler running....wouldnt of thought it would be pcb on boiler

 

[bewsh]

Ye the mid pos is definitely faulty. But the pump stops running as well after little while?

 

[Ermintrude]

Is pump wired off boiler or wiring Ctr?

 

[bewsh]

Ye the pump is wired from the boiler

 

[ed209]

Has the boiler temp setting been turned round higher than it was, I got a call to a profile the other day after gas networks bloke checked boiler after road repair, they only used to have it on setting no 2 he turned it to max and overheat in bottom tripped out
Shouldn't happen I know but the real world doesn't stick to the theory!

 

[bewsh]

It was on the max setting, but it's always been on that. But I don't think it's a boiler stat issue.

 

[ed209]

Just another thought and I have come across this on that model fan not sealed properly or the blanking cap for alternate position is missing or moved

 

[bewsh]

Cheers man, I'm popping back there tomorrow to change the mid pos, so I'll check that tomorrow. I've had that alternate flue position sealing cap missing before as well, co was off the chart!

 

[bewsh]

Another thought, does anyone know if the boiler has a built in frost stat?

 

[Ermintrude]

No . Not on solo. But that would only be when cold or if stat was pooped. System overheating when it's been on ??

 

[bewsh]

Ye I didn't think it did, but thought I'd double check just in case it was knackered and keeping the boiler lit

 

[breakdown]

If your friend has fitted the fan check the casing has not pulled the clip on thermostat off. Had a job not so long ago overheating since serviced and that was the problem. Worth a check.