DIY Doctor UK DIY Forums

Thanks Steve - When I said that rad was on zero I meant frost setting. If I put rad on 2 or 3 it still belts out even in the summer when it is hot and just the water is on. Is this a problem with the thermostat on that rad 'cos then i can get a plummer in.

I did not realise you have to leave a rad on all the time to protect the pump - does the frost setting count as on?

Yes, when TRV set on frost - it still allows a little flow.
It also sounds as if this rad is piped to the HW circuit as a het sync / bypass.

also could be that the thermo valve is a one way type and fitted on the wrong end of the rad.