Protherm 80E D/H/W Problem

[Jabba The Cree]

I have a Protherm 80E boiler ,and up until recently it has been working perfectly. As of yesterday, it is constantly clicking in and heating the hot water to 70 degrees,even though the stat is set at 50 degrees. I have had a couple of gas engineers out to look at it . One says it's the PCB or a faulty stat,but advised me I'd be better off getting a new boiler. The other , who was a B.G. engineer ,checked over the boiler and said there is nothing wrong with it,and said the problem was caused by a pipe leaking somewhere,causing the water to be reheated all the time.I have checked everywhere in my house ,and there is no sign of leakage.
Any advice would be greatly appreciated.
Thanks

 

[ChrisR]

a pipe leaking somewhere,causing the water to be reheated

If it were a radiator pipe the pressure would drop rapidly.

If he means a tap water pipe, ..try turning off the water supply under the boiler. If it stops, he's right!

 

[ianmcd]

Yep agree with Chrisr, isolate the water supply to the boiler there will be an isolation valve/tap on the inlet to the boiler and if the problem you have stops when you close this then you have a leak on the hot water outlet somewhere,

 

[Jabba The Cree]

Thanks for prompt replies. Can you tell me if the leak would only need to be a possible pinhole leak e.g.loose compression fitting etc. ,or would it be more likely to be a larger leak.Also would it be on the domestic H/W or C/H. As I say I can't find any sign of water anywhere.I live in an old property,and the previous owner,completely renewed everything internally,but unfortunately he has concealed everything and made it very inaccessible The boiler is installed in a bedroom cup'd,and all of the pipework is concealed behind either boxing,or dry lined walls,but there are no damp patches.
Thanks