wrote in message
oups.com...
Hi,

Just to clarify, the upstairs rads are fine after I cleaned them out-
they get nice and hot.
I'll try your suggestion tonight.



Another thing it could be is an airlock in one of the pipes going to the
cold rads. The rad would fill OK through the other pipe but water would not
be able to circulate.

You can try and cure this by turning all the rads off except one of the cold
ones, turn off the circuit for hot water if possible (if you have motorised
valves just make sure there is no HW demand), if you have an auto bypass
valve turn it to the highest setting after making a note of the current
setting, switch the pump to its fastest setting and then turn the heating
on.

If this doesn't work and you have a F&E tank, you could try the same but
using a hose blast some mains pressure water down the F&E outlet, or take
the rad(s) off again, open each valve and use the hose to try and clear the
air lock (this last one is likely to get you wet!)