Cold towel radiator

[coxius]

I recently replaced and old towel radiator (which worked fine) with a new radiator and TRVs.

The new radiator was cool (although the pipes near the floor were hot). I then replaced the TRVs with standard valves (as I read here that TRVs and hot water circuits don't work), and got a hot towel radiator. All seemed good!

Now (a few weeks later) the radiator has stopped working altogether. The pipes leading to it are cold, but the hot water pipes and the hot water tankin a different room are all hot. Radiator has been bled - no air, just lots of cold water comes out of it.

The radiator is connected to the HW circuit. The central heating has a HW tank and a CH header tank (gravity fed - I think you'd describe it). Old Potterton boiler. In the past, Ive turned the radiator off (ie in summer) and we still get hot water, so I guess it is tee'd off somehow from the HW.
It'd be difficult to find out where pipes go as the bathroom is tiled floor (and old house so pipes go all over).

Any thoughts? Is there a valve somewhere that I don't know about? Or am I missing something really obvious?

Advice appreciated, as the girlfriend is complaining about being cold in the bath.

 

[bengasman]

If a rad is working and then suddenly stops, it is unlikely to be a hidden valve. Sounds like an airlock or air in the rad, or balancing off.

 

[coxius]

thanks bengasman!

I've tried bleeding the radiator and got a litre or so of cold water and no air. If there is an airlock nearby but not in the rad, is there a way of finding it and removing it?

Is balancing relevant, as the towel radiator is on the HW circuit (and presumably the HW only goes to this radiator and the HW tank?)

Again, any thoughts much appreciated!

 

[alan m 1974]

Have you got a gate valve on h/water circs near cylinder,if so turn off and see if rad gets hot,iof it does,open valve enough to let heat through

 

[coxius]

Took radiator off wall, turned valves on full to blow lots of water through - airlock came out and rad now works.