Biasi Prisma 24SE Boiler - Central heating always ON !!!!!

[Monkeyboi]

Help ! . I have a Biasi Prisma 24SE combi boiler and the central heating will not turn off. I have turned the dial to winter and summer mode, turned the clock to every position and nothing. The thermostat in the hallway clicks as you pass the current temperature but the boiler refuses to stop pumping the hot water to the radiators. The DHW is fine .

The long , short and tall of it is - if the boiler is on then so is the central heating. I am having to turn the boiler on when i want hot water then off again to stop the house heating up like the tropics.

Any ideas as to where to start ??

Thanks

 

[tazman]

Hi, I had a similar problem with a Biasi Prisma 28se and it turned out to to be due to moisture in the CH micro switch. I think I picked a suitable spare up from Maplin's for a couple of quid.

 

[LUNAT]

HI

1.CH microswitch stuck
2.wires on the programmer faulty

 

[Agile]

Its actually the hot water demand switch failed as a result of water leaking from the gland.

Its really a CORGI job as the gas valve has to be removed to do the job quickly.

I did once hear of a DIYer who did it by removing the entire LH hydraulic block though.

Tony

 

[Monkeyboi]

Thanks for the help guys. The curious thing is that it has started working again ? I will get an engineer to come and look at it as you suggest .

Thanks for the replies.

 

[Agile]

I think you really mean that it has stopped working when not expected.

That will happen when it dries out after a time without using DHW.

Tell the engineer to bring a new flow switch and gland and make sure he cleans the operating pin throughly.

Tony