Radiators hot upstairs/ cold down / potterton boiler / myson

[GAKent]

We've just turned on the heating for the first time this year and the boiler (a Potterton Suprima 30L-100L) was making some funny clunking noises.

The radiators bar one upstairs are working as is our hot water.

Downstairs all radiators are cold.

When the hot water is turned on the Myson Power extra light in the airing cupboard is on (the LED green on the casing), but when I turn on the central heating it goes out.

Could the problem be a pump or a valve or is it something more serious. How much will repairs cost?

Many thanks!!

 

[Elkato531]

Shouldn't be the pump if the hot water is ok. The fact that the upstairs rads are on also suggests that the motorized valve is ok. Turn on HW and CH and check whether the pipes out of the motorised valve get hot.

Check you header tank in the loft has water in it. Vent all radiators and make sure the pump is at max speed. Turn off all rads which are getting hot to force water round the rest of the system. If this doesn't help, turn off all rads bar one to force circulation through that rad. Proceed one rad at a time. If you've got air trapped somewhere this should force it through.