Anyone know about thermostatic radiator valves?

[chillipickle]

Sorry, this is quite dull, but just wondering if anyone can help.

The radiator in our spare room is set to "*" but still gets hot. I googled it, and if I unscrew the valve there is a pin underneath which should press down easily and pop back up again, but apparently they often seize if they are left in the same position for a long time, so the valve may be stuck open.

I had a look and sure enough the pin can't be pushed down at all. I tapped it gently a few times, but this didn't free it up, so I decided to have a look at a valve on another radiator to see how far up the pin should come, and how easy it is to press down.

I have just taken off the top of every single valve in the house, and in all of them the pin can't be moved at all. Is it possible they are all stuck? Or am I missing something?

We have only lived in the house for a few weeks, so I have no idea if they have all been left in the same position for years on end. They are Drayton valves, if that makes any difference. Can anyone advise?

Bang the pins hard with a hammer, then smear pin with vasoline and push in and out a few times,

I would try not to use a hammer, as you may bend or break them.

They have to be pushed down quite hard. The best way I know is to use a steel soup-spoon in the palm of your hand. The curvature of the spoon means the pin is motivated to stay upright rather than bending sideways. Pressing with any other implement tends to bend them over. In fact, fitting the knob back on, and winding it up and down, exercises the pins. When they stick, they usually stick down (closed)

You can apply a drop of WD40 with a tiny paint brush or the point of a pencil. Apply it to the top of the pin so it runs down through the pin hole. Leave it a while and do it again. No use spraying it around the outside.

When you are refitting the top of a TRV, adjust it to the hottest it will go, so you are not trying to push the pin down as you screw it back.

How old are your TRVs, and how old? If they have a grey or white plastic body, with a chrome flat-topped dome coming up, they are probably Drayton TRV4 or similar, which used to be the best (the new Danfoss RAS-C2 is even better) and you can still get replacements which will fit in with no pipe changes required (but the system will have to be drained if you are changing several). However if they are TRV4, you can fit a new thermostatic head if the old one fails without draining.

Because TRV4 used for many years to be the best, they got a good reputation and sell at a premium price.

Do you like DIY plumbing?

Gosh, thanks PigletJohn for the very comprehensive reply. I will try spoon/WD40 later today.

One further point that you may be able to clear up - I thought the pins in several other radiators were also stuck, but we tried turning them down to frost setting and they did go cold. From reading around I thought that the pins should be easy to push down normally (in which case a stuck pin would be easy to spot), but is that not the case?

And as you seem very knowledgeable on these, do you know what temperature the frost setting kicks in at? Another possibility is that it's working fine but just heating up because the room is below whatever temperature that is. Though I imagined it would only switch on if it got properly cold, and our house isn't that chilly.

Yes they have white plastic body with chrome flat-topped dome, and I think one of them is a Drayton TRV4 as per your link, and the others just say 'Drayton' - but could perhaps be an older model? So hopefully we could replace just the heads if needed. Trying to avoid DIY plumbing if at all possible! We have only just bought this house after years in rented accommodation, so we are fairly clueless about all this home maintenance stuff. (But learning quickly!)

it takes quite a lot of effort to push them down. I couldn't do it with my thumb.

the frost setting, you could have a look on Drayton website, but I'd guess about 5C

older and/or cheaper thermostatic heads sometimes stop working and fail "open" (pin up). The technology is different but I forget why. I think the better ones have a wax element like car radiator thermostats but I might be wrong. If some of yours are older than TRV4 it will probably cost you more to buy a new head than to change the valve. See if all the heads will fit all the valves. Be sure to wind the head to max temp before you try to fit it.

When pins jam in the valve body they usually (?always?) fail pin down (shut)

There used to be a TRV3 that is not compatible (and presumably a TRV1 and TRV2)

Have you tried kicking them? If it doesn't work it may make you feel a bit better!!

P.S Put on shoes first!