Puma cutting out

[tomcubi]

I Have a similar problem. I hope to get a few tips. I wouldn't like to replace this Potterton PUMA 80 which is probably 10 years old, as we'll have to renew the whole system in 6 months, but the pilot keeps cutting out.
It happens when the central heating turns on. Today I ran the hot water several times and the pilot never cut out, but suddenly this evening some steam started to come out from the air vent 2 mins after the central heating turned on.
I'd be very grateful for any advice you can give me on this.

 

[ianmcd]

could possibly be that the pump has failed but more common with this boiler is the wax capsule on the diverter valve, you used to be able to buy the capsule seperately but dont think you can anymore think you need to buy the complete unit but trust me if you just split the new one and replace the capsule as its a nightmare to change the complete valve , if it turns out that it is the pump buy an ideal multi head pump its less than half the price of the manufacturers pump head

 

[tomcubi]

Thanks Ianmcd,
so the wax capsule basically would block the CH system overheating the water therefore cutting out the boiler?
If the hot water is working ok, could the pump still not be working?
If you turn the CH on after 60 secs you can see steam and light drops/spray of boiling water from the air vent.
The temperature sensors could not be the problems?

 

[ianmcd]

the wax capsule diverts the flow of water to either radiators or just circulates around the boiler to give you hot water, when you swith over to heating and the wax capsule is stuck in the HW mode the water gets extremely hot inside the boiler as it has no where to go , I definately think it is the capsule that is at fault but checking the pump is easy as it runs ok in hot water only mode just run a tap and put a small bowl or cloth under the pump and slacken of the finger tight nut at the head of the pump and you will soon know if the pump is running or just feel the pump you can usually feel vibration if it is running but Definately think it is your wax capsule or you wouldnt get Hot water either

 

[tomcubi]

Thank you very much Ian.
I'll see if I can find the wax capsule elsewhere, as they sell the diverter valve assembly complete.
I think you are right in fact I turned the CH on and after 2 mins the 22mm flow pipe was still totally cold, but the water was boiling towards the air vent.
I'll let you know

 

[tomcubi]

I changed the wax capsule, but hasn't made any difference: as soon as I turn the CH on, after 1 min, the boiler cuts out.
Either faulty pump or central heating sensor causing boiler to go to high limit and cut out pilot? Or having good pressure hot water means that the pump is working ok?
I tried to see if the pump vibrates, but I'm not sure, the whole boiler vibrates..

 

[powell30]

Unfortunately sometimes you need to replace the diverter section not just the wax capsule.

They are dammed hard to get off too if the back nut won't come off easy......doubt it's the pump.....you would get thermal transfer into the flow pipe at least a little way.

 

[tomcubi]

Thanks Powell30!
I appreciate your help.

 

[bengasman]

Don't you think one thread is enough?

 

[tomcubi]

Sorry, but I didn't start this thread, everything started here by chance as you can see.