DIY Doctor UK DIY Forums

Hi
It appears to be a common problem but I have had hot radiators upstairs and cold downstairs, I then lost all hot water.
I removed all downstairs radiators and flushed them out, I have put fernox cleaner in the system.
I now have hot water again but 3 downstairs radiators are stone cold.
When I switched the heat on I bled one radiator to see if hot water would come into the radiator. The return pipe got very hot to touch but the flow pipe stayed cold. When I stopped bleeding the system the pipe went cold again.
The pump is a Grunfos 15/50 and is approx 4 years old.
We have a Potterton Netaheat Profile boiler.

Thanks for any help as I am now very confused!!!!!!!

try turning off the radiators that are hot see if the heat gets to the ones that are cold could just need balancing.

Thanks for your reply.

I turned off all the hot radiators and left one of the cold ones on, this had the desired effect and two more radiators got hot.
The last one I traced a blockage to the top of the vertical drop underneath the floor boards, I found out it was blocked as when the system was running I could take the flow valve off and no water came through.
I am not sure if what I did next was ok but it worked, I have a compressor and sent a quick burst of air up the pipe, I heard gurgling then a big black plume of water came out of the pipe, I forgot the system was on and the water was boiling, I managed to get the pipe reconnected and now the heating is all back on.

Thanks for the advice.