Heating not working properly unvented microbore system

[The Plumber Guy]

Hi all,

I'm trying to find out why an unvented microbore system isn't working as it should. The boiler works fine but when I got to it this morning the system pressure was at zero bar. I filled it up to the working pressure, turned on all TRVs and lockshield valves and bled the system fully. The upstairs rads work well mainly but a few aren't as hot as the others. Downstairs two rads work fine but the rest - all 6 of them - are cold or lukewarm. The feeds to the trvs are hot but the pipes below the lockshield valves are still cold and there is no heat in the rads.

If there was a blockage I think it would only affect one rad and the cold ones ran hot when I drained hot water through the drain valves on the lsvs so I really have no idea why the heat isn't going through the rads.

The pump appears to be working so I have no idea why only half the rads are heating up and not the other half. Please help!!

Many thanks

 

[Billy Bob Bob]

pump or balancing issue,what boiler?

 

[ecowarm]

You turned on all lock shield valves? you've messed up the system ballancing probably

 

[The Plumber Guy]

Sorry, just to add to the above, the rads weren't working BEFORE I refilled the system. When I turned all the trvs and lockshields off upstairs so that only the downstairs rads could heat up, they didn't. The problem was the same - flow heating but return cold and no heat in the rads.

 

[stevew451]

throttle down lockshields on working rads and is pump strong enough

 

[charliejamesuk]

Check PINs aren't stuck on the TRVs?