Baxi solo 3 pfl 50 won't fire up til it cools down.

[222davidk]

Hi all, I am a new recruit and hope somebody might be able to shed light on my boiler problem. I have just had a gas man out and he is stumbled. Basically my baxi solo 3 pfl 50 works perfect for approx 25 mins. Does what it is supposed to do. But after 25 mins its knocks off and I have to wait approx 20 mins to come back on like it has to cool down. No overheat lights come on. The fitter has replaced the pcb, pressure relief valve and had new fan fitted. When it comes back on it work's fine but then knocks off again. Any help I would appreciate immensely.

Rgds dave

 

[Joshls]

I know this was a while ago but did you ever find a solution? I have the exact same problem.

 

[222davidk]

I know this was a while ago but did you ever find a solution? I have the exact same problem.

It was the pressure relief valve. First one was faulty.

 

[Gerryk]

I know this was a while ago but did you ever find a solution? I have the exact same problem.

Im having the same problem,,baxi solo 3 heats up,reaches temp then wont come back on until system cools down and i turn the heating back on,,i changed the thermister but still having same problem,,did you fix yours?

 

[Joshls]

Im having the same problem,,baxi solo 3 heats up,reaches temp then wont come back on until system cools down and i turn the heating back on,,i changed the thermister but still having same problem,,did you fix yours?

Yes, it was the pressure switch attached to the fan at the top of the boiler. The nub on the micro switch decays over time and becomes worn, so from a cold start the boiler turns the fan on, the micro switch activates and the firing sequence continues. Once the system is up to temp the boiler switches off, however, the microswitch doesnt return to off, so the boiler is in a sort of error state. When heat is called for it wont start because the diaphragm is saying the fan is on when it shouldn't be.
Someone competent should pull the fan out at the top and check the nub of the micro switch on the diaphragm.
We didnt even have to replace the whole thing, we purchased a micro switch for £1 and took the nub out of it then disassembled the one on the boiler and replaced it with that. Its literally a tiny peice of decayed plastic.
Dont open up the actual diaphragm housing, theres no need.
Let me know how it goes.

 

[Gerryk]

Yes, it was the pressure switch attached to the fan at the top of the boiler. The nub on the micro switch decays over time and becomes worn, so from a cold start the boiler turns the fan on, the micro switch activates and the firing sequence continues. Once the system is up to temp the boiler switches off, however, the microswitch doesnt return to off, so the boiler is in a sort of error state. When heat is called for it wont start because the diaphragm is saying the fan is on when it shouldn't be.
Someone competent should pull the fan out at the top and check the nub of the micro switch on the diaphragm.
We didnt even have to replace the whole thing, we purchased a micro switch for £1 and took the nub out of it then disassembled the one on the boiler and replaced it with that. Its literally a tiny peice of decayed plastic.
Dont open up the actual diaphragm housing, theres no need.
Let me know how it goes.

So not the pressure relief valve?? I didnt think that would have anything to do with,,ive been looking online the last few days and people did mention the air pressure switch,,ill go to my suppliers and see can i get a micro switch,,thanks for the quick reply ill let you know how i get on

 

[Joshls]

I'd highly recommend replacing just the nub OR the entire pressure switch unit. The actuation force of the already installed micro switch needs to remain the same, do not swap for a new microswitch with a different actuation force.
This is why we went to the effort of disassembling the switch and swapping just the worn nub.
Youll be able to see once you remove the switch if it's worn.

 

[Gerryk]

I'd highly recommend replacing just the nub OR the entire pressure switch unit. The actuation force of the already installed micro switch needs to remain the same, do not swap for a new microswitch with a different actuation force.
This is why we went to the effort of disassembling the switch and swapping just the worn nub.
Youll be able to see once you remove the switch if it's worn.

Changed the air pressure switch and boiler working fine now,cheers!