Ensuite and bathroom rads coming on

[chad5k1]

Hi
I've noticed that the rad's in the two bathrooms upstairs are coming on even when the heating is off. I've got the room stat turned right down to the lowest setting yet every morning when I go into the either of these rooms the rad is on. No other rad in the house is on. Could it be plumbed into the HW curcuit? How could I tell and is this a problem?
The house is about 20 years old and has a potterton 80e boiler and 3 way mid position valve (that was replaced last year).
Thanks
Rich

 

[ChrisR]

It may well be plumber such that you get warm bathrooms whenever the boiler comes on. Fit TRVs to control it, though nb your boiler needs a bypass, and one of the the bathroom rads may need to be left open if there isn't a separate one.

 

[chad5k1]

both rads have TRV's, but i was slightly concerned that if they are on the HW system that turning them off may stop the flow of HW. I guess if it's been plumbed proplery this wouldn't be the case as it should just be a T off the HW pipework.

 

[ChrisR]

I guess if it's been plumbed proplery this wouldn't be the case as it should just be a T off the HW pipework.

No you've missed the point. It's probably plumbed off the boiler output before valves which control CH and HW. Otherwise you wouldn't get warm rads in the bathroom UNLESS the HW was on.
This roiute can also be the only bypass. If there isn't a path open the boiler will overheat.

 

[chad5k1]

I understand now thanks.
How would I be able to find or know if there was a bypass? Seems like a bit of pony job to call a plumber in for....