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alex hewitt
alex hewitt, HVAC Technician
Category: HVAC
Satisfied Customers: 108
Experience:  10 years UK based boiler repair and servicing. Registered gas operative in Uk
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My Potterton Boiler keeps cutting out - the overheat nipple

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My Potterton Boiler keeps cutting out - the overheat nipple underneath the boiler clicks out. In order to remedy the problem I had the ch pump replaced and the heat override thermostat in the boiler replaced less than a week ago. But the problem persists when I reduce the temperature of the main thermostat. The engineer who came round said that if it happened again I would need my system powerflushed at £700. But I don't understand why that will solve anything! Help!
Additional Information: before the pump and heating circuit were changed the boiler cut out regularly. Now it only seems to cut out when I manually alter the room thermostat. I don't understand why flushing the system will solve what appears to be an electronic/electrical problem.



Your engineer quite correctly has highlighted the common faults that cause a boiler to lock out ( ie over heating) namely a faulty limit stat and failing that a lack of ciculation through the boiler hence a replacement pump.


By flushing out the system you remove the sludge and any other debris that could be reducing the flow of water.


Similar results to power flushing can be achieved using a heavy duty cleaning agent and flushing out without a power flusher but it does take longer.


£600 to £800 for power flushing is not unusual.


A cleaning additive cost around £20 and you leave it in the syatem for a period of time . Then flush the system through with a hose etc..


Hope this helps



alex hewitt and other HVAC Specialists are ready to help you
Customer: replied 8 years ago.
Thank you but is this the only remaining solution as you refer to 'common faults'? Are there any other possibilities in your view that could be causing the problem? Can I be sure that the boiler is locking out because of over-heating rather than say an electronic fault? It just seems odd that the lock-out occurs when the system has cooled down because I lowered the temperateure - if you see what I mean. If I don't alter the thermostat there has been no lock-out since the repair.


Having changed the component that controls overheat lock out, it narrows it down.By lower the stat on the boiler ( as opposed to the room stat )will reduce the likelyhood of over heating. If lock occurs having reduced the room stat the system temperature will still remain the same but will stop calling heat sooner and perhaps shuts off the pump too soon causing lock out.


I think flushing out is a good course of action and as to whether you decide on power flushing is down to you ( two schools of thought about power flushing!)



Customer: replied 8 years ago.
Thank you Alex, I think this answers my query completely. Do I owe you anything more?


Hi John


Glad to help and always grateful for a bonus!



Customer: replied 8 years ago.
I will if i get that option lol! What part of UK are you btw?

I.m in the cotswolds, born and bred.



Customer: replied 8 years ago.
OK ty next time I'm at Heythrop Park ..........

Not too far from me , Chalford .

Customer: replied 8 years ago.
Sorry Alex I cant work out how to pay you a bonus at this point. The system only allows me to pay you the same amount again as the first question.