Lockshield valve hot, Radiator cold

[wardr77]

Don't know if anyone can advise what to do. Have two radiators which will not heat up, the lock shield valves are hot but the rads are cold. The TRVs are bi-directional Danfoss units and have been turned up for max heat. All other rads in the house work ok.
I have also gone through the process of bleeding the rads and shutting off all the other rads in the house to force hot water through them but no luck, they got marginally warm but that was about it, any ideas?

Many thanks in advance

 

[sircerebus666]

Trv pin sticking , blocked trv or lock shield , sludge build up in rad, pick one or a combination of the above

Remove trv head pull up pin (if you can ) , turn up lock shield fully (noting number of turns to do so) and see what happens

 

[terryplumb]

TRV pin stuck would be first thing to check. Do not pull the pin up ,but press down on it .If the pin does not move up and down a couple of millimetres ,try tapping the pin with a block of wood or similar to free it up.

 

[wardr77]

Thanks for your replies. I pushed down on the TRV pin and that moves freely, also opened up lock shield fully, but no luck. Do you think sludge is causing a restriction in the flow?

 

[terryplumb]

When did these two rads last work properly ?
Is your system sealed / pressurised or fed from a loft tank ?

 

[wardr77]

Good question, moved into the house in Feb this year and do not remember them working to be honest. The system is a MegaFlo system, which I believe is an unvented system. There is a small tank in the loft but assume this is to keep the central heating system topped up?

 

[terryplumb]

Megaflo provides pressurised domestic hot water to taps.
It's the central heating system I asked if its pressurised.
What is the make and model of your boiler ?

 

[wardr77]

I see... The boiler is a Worcester Greenstar. Thanks

 

[terryplumb]

Greenstar covers a range of boilers,so none the wiser. But if you have a small f&e tank in the loft, that is still in use ,the system is not sealed.
As we don't know if the rads ever worked ,you will need to do some investigating to establish why they don't heat.
As a previous contributer advised ,blocked or faulty valves ,blocked pipe ,blocked rad , incorrectly plumbed in are all possibilities.
Are the rads vertical designer type ,or conventional panel radiators ?
The way forward depends on how much you wish to do yourself ??

 

[wardr77]

Ok difficult to determine the exact model of the boiler, its a floor mounted 85cm tall 30KW boiler with Greenstar on the label, other than that I cannot see any further information, there is an instrument panel that opens up and and a couple of green illuminated numbers than sit around 60, but have no idea what that means, no manual to hand unfortunately.
Rads are conventional panel type, I dont mind removing the rads and giving them a flush out and see if that helps if you think that is a good idea, anything more than that I will call in professional help.

Thanks for your advice.

 

[terryplumb]

If you close the TRV on all other radiators ( don't touch their lockshields) make sure the lockshield on rads that do not heat are fully open ,and close the trv on one of the rads that do not heat ( so one of the rads that doesnt heat has both of its valves fully open) and run the central heating what is the result ?

 

[wardr77]

Just done that, all rads cooling down but the two that do not heat up, no change, including the one with both valves fully open.

one of the rads in lounge stays hot... probably a TRV issue not known before!

 

[terryplumb]

You need to close down the lounge rad .we are trying to concentrate the flow from the pump through the one problem rad that has both it's valves open.

 

[wardr77]

ok but closing off the TRV on the lounge rad doesnt do anything it stays hot, so should I close off the lockshield on this one?

 

[ianmcd]

post a few pics of your boiler, every WB condensing boiler is called a greenstar