Ok, conventional S type heating layout, pump seems to be running 24/7.. Hot water and heating both off. Think pump is fed from birds nest of wiring in airing cupboard, prob not from boiler downstairs.

I’m guessing this might be a stuck 2 port valve on the heating side? Any other likely culprits?

Thanks,

Jeff

If it’s a proper S plan, then it’s probably a stuck microswitch in one of the heads

Don’t know if the S-type, Y-type thing makes a difference, however some conventional boilers have a permanent live to the pump to circulate hot water after the system switches off, but all day is excessive! If it’s this it’ll be the boiler circuit board at fault