Radiator Valves Issue

[BigRooster]

I’ve got radiators fitted in my caravan from a combo boiler.
The issue I have one radiator always takes an age to warm now it’s staying cold I’ve done the the usual bleeding tapping the TVR but now I’m thinking it could be the lock shield valve.
The pipe going to the lock shield is hot the TVR pipe is cold . What is confusing me traditionally the the lock shelf that’s were the water exits the radiator and water goes in via TVR .

[Atheist]

Have you tried checking that the lockshield is open and not closed? You pull off the plastic cap and grab the flat-sided metal pin with pliers or adjustable spanner and try to turn clock and anti-clock. Anti-clock opens the valve and clock closes it.
The TRV might have an indicator arrow on the valve body showing which way the water flow should be. If it's pointing towards the radiator then the TRV should be fitted on the flow pipe, not the return. If the LS pipe is hot up to the valve it might indicate that the valves are fitted on the wrong ends of the rad, but it's hard to see why that should be the case. Did the rad work properly in the past?

[Atheist]

The pin in the TRV could be stuck in the off position. Have you tried removing the TRV head and checking to see if the pin is stuck down. If so a little pushing and pulling might free it. Pliers might be able to grab the end of the pin if there is enough pin sticking out, and you could then try to pull it up. Tapping alone might well be insufficient.

[BigRooster]

They had been working and all the rads are fitted the same

[Atheist]

Is the pipework surface mounted so that you can see how both rads are connected? If the system is left off until it cools, you can then turn it on again and check to see how the good rad is connected, i.e. flow or return, by feeling the heat travel along the pipes to see if the TRV or the LS pipe gets hot first. I would expect the TRV ro be on the flow. If both rads are piped up the same way, then it suggests that the rad or pipework is blocked or one of the valves is closed.

[Atheist]

Could it be a balancing issue? If you close the LS on the working rads and make sure the bad rad has open valves, then if it gets hot quickly it might be that the other rads need to be throttled back so that the bad rad gets a better share of the hot water flow. If the bad rad still doesn't heat up, then there must be a blockage, either sludge in the rad or pipework, or a dodgy valve.

[BigRooster]

Going back next weekend I’ve bought new valves if the rad is blocked then this could be a good time to clean it out . The pin on the TVR works

[Atheist]

Good luck. If you sort it, maybe you could let us know what was the problem.

[The Builder]

The first thing I would try is Atheist's comment at 12.59.
Shut down all rads except the suspect one, and fire up the boiler.

If the rad works, then it's possibly a matter of balancing.
More likely though, is a small airlock in the pipework. With all other rads closed, the boiler pump will force the flow through.

[BigRooster]

Yes I will do that throttling back could be a good call

[bhg481]

If you close off all the lockshield valves make sure you count the turns as you close them as you will need to open them the same number when you re-start the system. The lockshields are used in balancing the system and should NOT be just opened fully when you've finished; the valve compensates for the differing lengths of pipe to each radiator.

[Atheist]

further to bhg;
1 count and write down the turns on each LS as you close each one
2 check to see if that causes the bad rad to function.
3 if it does function, then I suggest you open the LS's the same number of turns as when you closed them.
4 If a blockage or airlock has been cleared, then all the rads should now function properly
5 If the bad rad is still bad, then try balancing by closing each LS a bit, so that they are all throttled back a bit but still working.
6 It's all a bit long-winded, so continue until you crack it or give up.