Help - One radiator not working. Piglet John??

[Coconutfeet]

We had a radiator removed to have some work done and since it's been replaced it's not heating up at all. All the other radiators in the house are lovely and hot. (Combi boiler if that's relevant)

I've bled the rad and it's definitely full of water. I've taken the top off the TRV to check that the pin isn't jammed. It seems to be fine.

The pipe coming up from the floor going into the thermostat side is cold. The pipe on the other (lockshield) side is warm but the radiator itself is stone cold.

It's a Drayton radiator and the lockshield looks something like this. I've been tightening and untightening the the nut thing at the very top of the pipe thinking that might do something but it's not making any difference. All references to lockshields on YouTube help pages look completely different so I've no idea if I should even be doing that. Can anyone help?

Surely there's a blindingly simple answer to this problem and we've missed something really obvious. Thank you!

the thing in your link is not a lockshield.

It probably looks like this Under the plastic cap is a metal spindle which rotates like the spindle of any other tap. You may find that the knob off another radiator fits it. The spindle is brass and easily damaged by pliers. You don't turn the nut. Don't adjust it yet.

First, turn off ALL the other radiators in the house. Does this one then get warm?

Take the thermostatic head off the TRV. Turn it to its highest setting (otherwise you will not be able to fix it back on). Put a metal soupspoon in the palm of you hand. Press directly downward on the TRV pin (not sideways or it may break). The spoon will help centre it. Does it go up and down? You can drip WD40 off the point of a pencil onto the pin if it is stiff (squirt it into a jamjar and dip the pencil in).

are the pipes to the radiator the size of your finger, or the size of a pencil?

Does the TRV look like this? How old is it? Who fitted the radiator, and when?

It's not a chrome towelrail or a tall radiator, is it?

p.s.

loosening the nut on the pipe will make it leak.

Thanks so much for replying Piglet John. Yes, I did make it leak .

So, I've turned all the other radiators off and but still no joy.

The radiator is pretty old (don't know exactly but at least 10 years) but was working fine previously (system had been rebalanced last year by the gas engineer when we had some stuff done on the boiler). It was then removed and replaced by a workman doing some work to the walls which has caused the problem.

The pipes to the radiator are slightly fatter than my finger. Definitely not pencil sized. It's the largest radiator in the house. Not a towel rail.

The TRV does look like the one in your link. I've taken it off and checked with with a spoon and it moves up and down easily.

There's no plastic casing on the thing at the other end of the rad (the lockshield??). It doesn't appear to have sticky up bit like the spindle on a tap (some of the other radiators do under a plastic casing, but not this one). I've put a picture of it on my profile. Is this the lockshield? If so, should I be doing something with it?

I think it may need bleeding.
You need to turn heating off so that cold water comes out.
Put a bucket underneath to catch the water then untwist the nut thingy.
If it is just the one radiator you don't need to do the others. When the radiator is empty, screw nut back. Then put boiler back on and your radiator should start to get warm.

you say you have bled the rad, and the TRV pin moves freely. Put the thermostatic head back on. If your system is an old one, there might be a sediment problem. The way to check would be to take the radiator off (with both valves closed) then open the valves, one at a time, and let them gush into a bucket.

However first we need to get that lockshield working. The next thing to do would be to open it by a turn or so. I'm not sure I recognise it, but it looks like an old version of the Danfoss where you take the cap off and use a special tool to turn the spindle. Compare yours to the pic in my link. Try emailing a pic to Danfoss, they should be able to confirm and send you the tool, possibly free or at modest cost, and I am sure they can email you the instructions.

post back if they quote an excessive price for the tool. It is only like a splined Allen key IIRC. I just had a look at a new Danfoss lockshield, the chrome dustcap on the top comes off with the fingers, and has the makers name engraved on it.

Or give up and get the plumber back.

Just in case it is an airlock, leave the heating on overnight, and the TRV on max, and all the rads, except the one in the room with the wall stat, turned off.

Forget all the crazy AnyFucker adulation PigletJohn is the best MN'er ever

Oh dear

Have I got to say AMAB?

try

this one

I agree TheFuckersonInquiry!

Thanks so much Pigletjohn for taking the time to respond. I really appreciate it.

I think you could be right about the lockshield. It does look similar to the one you linked to, although without the makers name on it. I've emailed Danfoss, so let's see what they say.

Meanwhile, I'll leave the heating on as you suggest in case it's an airlock.

" Just in case it is an airlock, leave the heating on overnight, and the TRV on max, and all the rads, except the one in the room with the wall stat, turned off."

We've got an old dial thermostat in the hall, and a digital thing that you use to turn the heating on or off and set the timer etc in a cupboard. Do you mean that I should leave the radiator in the hall on as well as the one that doesn't work?

Aha! Just seen your second message. it's just a regular allen key? Great. Will try that!

yes, leave the hall one on overnight, otherwise the pump will be thrashing round with nowhere to go. if that's where the room stat is, that radiator should never be turned off.

OK, so it doesn't seem to be the one you linked to, instead it's got a slit in it. Do you think I'm ok to try using a screwdriver to turn it? I'm a bit anxious about causing serious damage...

Also, should I be doing this with the heating off, so heating off, a quarter turn, replace cap, heating on and test, then heating off, another quarter turn and so on until it's open? There's a bit of water coming up into it, hopefully that's not a problem once the cap is tightly back on? [anxious]

I would try it with a screwdriver. It might be an old model; or it might even be that Danfoss bought or licenced the design from another maker. Let's assume for the moment that it is the same.

close it fully, then open it 4 turns. If the rad then heats up, close it, then open up just one turn, and verify that the radiator is still hot.

If it is fully open, and flowing well, it will tend to steal flow from all the other rads. Even open by half a turn should be enough for the rad to stay warm.

BTW if it is leaking, then you ought to get it replaced, even though the dustcap may hold it back. Valves should not leak, it is probably just old and worn out. If you have mostly Drayton TRVs, try to get a Drayton lockshield (or whatever make most of the others are). If you have several of the probably-Danfoss, they are probably all the same age and would all benefit from being changed in one convenient go.

If this, or any other valve, starts to leak round the spindle, quickly turn it all the way open, or all the way closed, and it will probably stop.

Thanks again pigletjohn. I'm going to tackle this tomorrow now.

Just back to say thanks for all your help with this Pigletjohn. Unfortunately it's so old that it's really corroded so I've given up and called a plumber who's able to replace the valves. Thanks to you I was able to give him a coherent explanation. Anyway I really appreciate the time you took on this. I've actually found it quite interesting learning how radiators work.