Radiators constantly hot despite TRV's being turned off

patchyX2

I've recently moved into a new home. There's 4 radiators upstairs and they all get screaming hot, but the TRV only works on 1 of them. Even when turned down to zero/snowflake, the other 3 rads remain screaming hot.

I've taken the TRV heads off and tried to move the pin (it's more of a cone with a flat top rather than long skinny pin). I've used WD40, tapped gently with a hammer, jiggled it around with pliers. Pushing down 1 of the valves moves it 1-2mm then springs up, the other two don't move at all (that I can tell).

I bought a new head to see if the TRV head was knackered, but it still behaved the same.

I know the correct approach is to get a plumber in, drain the system and replace the valves, but the quotes I've had are too high considering I'm going to be ripping all the rads and most of the pipework out next year due to extensive renovations.

I'm not confident enough to replace the valves myself. Is there any kind of simpler tweak/bodge I can do that might help? Perhaps adjust the lockshield on the other side? I don't mind if the radiators are permanently cooler (as long as they aren't disabled entirely). In fact this would be preferable because the upstairs is so much hotter than downstairs.

FreeBear

Short term fix is to lower the flow temperature. It won't help with a seized TRV valve body, but it will mean you don't scald yourself on a burning hot radiator.

Turning the lockshield down won't help much, although you could shut it off if you don't need heat in a particular room - Just remember to open it up again when you need to drain the system down.

marcia_

 When my heating went crazy and wouldn't go off it turned out to be a valve where the dual zone controls were. They replaced the valve and it fixed it. Do you have zoned heating? 

ThisIsWeird

Hi Patchy.

Check Marcia's point first. Is there a separate wall 'stat upstairs, for example?

Otherwise, yes, just turn the lockshields down, even fully off. 
L/S's are, in effect, 'manual' control valves with the nice knurled knob taken off, replaced by a shiny smooth one that spins loosely so you can't accidentally adjust it.
You can turn a L/S valve on and off on a daily basis if you want - it'll last as long as any other valve - years.
So, yes, that's your solution - l/s either down or fully off.
It's always worth noting its starting point - how 'open' is it to begin with. So mark the spindle, and close it clockwise, counting the no of turns and parts turns this takes. Write that down for each l/s, so you can always return it to that setting should you get your TRVs fixed.
If you pull the smooth cap from a L/s, could you post a photo? You should be able to get proper knobs for it, perhaps on eBay - that'll make them easy to control.
Finally, I think it may be worth getting a wee tube of silicone grease, and opening each l/s anticlockwise fully (the spindle will raise up a good 8mm or so), thoroughly cleaning the newly exposed section (show us a photo) using a toothbrush, and smearing sili around where it disappears. Then screw it fully back down - that should lube the rubber washer inside, and make it operate more smoothly, and last longer too. It ain't been altered in years, so may be a bit stiff to begin with.
While you are at it, also clean the pins on the TRVs, smear sili right down around the pin, and repeat your pressing-downs. Put something like a spoon over your thumb, as it'll hurt otherwise - the spring is quite firm. See if it loosens up - the full movement is around 6-8mm, should be smooth, and bottom-out with a firm thunk. 

If you are happy controlling the rads with their l/s's, tho', then don't bother trying to fix the TRVs too much as you'll be replacing it all anyway.

If the spindle has a slotted top, then these will very likely fit: https://www.ebay.co.uk/itm/224262366562

Otherwise, these - but they have mixed reviews: https://www.amazon.co.uk/Universal-Fitting-Replacement-Safety-Radiator/dp/B0080IKRMU?

Albermarle

Regardless of this issue, you should not really have radiators that get 'screaming hot' . Do you know what the boiler flow temperature is set at?

ThisIsWeird

Albermarle said:

Regardless of this issue, you should not really have radiators that get 'screaming hot' . Do you know what the boiler flow temperature is set at?

Good point!

Rodders53

Sounds like the Pegler Terrier style of TRV....  They do only move a very little, as you have described on the one that works... I have the same valves.
https://device.report/manual/5360782

Now you can (with suitable precautions of old towels and plastic sheeting) partly undo the 'gland nut' around that pin to hopefully free the stuck pin.  Press the pin up and down while loosening a tad at a time  using a suitable spanner and another tool (I use a 10 inch adjustable's handle to push in the flat top pin).  Some water may escape, retighten the nut to stop it.  Do not undo completely.  Half a turn or probably less is all that is needed, if I recall correctly.

Lubricate the freed pin with PTFE or silicone grease/ oil --- WD40 sell such sprays... But "Normal" WD40 has a reputation for damaging rubber O-rings due to the petroleum products in it (and they are used as seals in the TRVs).  So I'd suggest cleaning off what has been applied as much as you can before doing anything else.

You may find that the only proper solution is a new valve, though.