Potterton intermittant hot water

[emailrob]

My Potterton (Puma 80, yes it's fitted at last for those of you who were reading previously) has a small problem.

When I turn the hot water on, the hot water is almost instant, stays hot for a few seconds, then goes cold, then after about 30-45s goes hot again.

Based on other posts, could this be a thermocouple problem? The heating side of the boiler seems fine, it's just the hot water.

It does lull you into a false sense of security, when it blasts hot, you leave it to fill the sink, then cold water comes gushing out!

cheers as always

 

[COG]

The thermocouple seems to get the blame for everything, if it hasnot gone out then its ok (if you have one).without any more info or readings it could be anything. can you check your gas pressure into your gas valve on hot water and to your burner on hot water.[/i]

 

[Gees]

I agree the thermocouple is ONLY there to hold the gas valve open as long as the pilot light is running ok. If it goes out the gas valve will CLOSE completly. IE no heat at all Untill the valve it held on with the manual push button while the pilot is relit and then provdes the current to hold the valve OPEN. The gas valve is held open by an electromagnet that is powered by the thermocouple.... as soon as either the flame goes out or the thermocouple stops providing the current to hold it open the valve will close cutting off all gas. This is only relavent to older boilers NOT the modern types with spark ignition..

 

[emailrob]

thanks, at least it rules that out. I will check the other pressures, it's just a weird fault