TRV stuck shut

12 Feb 2017
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United Kingdom
One of my Drayton TRV has stuck in the off position, I can turn the TRV head from frost to max but the radiator just won't get warm, I've bleed it and get water out so i know its not air locked. The next 2 radiators on that pipe run are both getting hot as is the pipe work directly by the tee offs to this rad. I've removed the TRV head and the pin goes up and down freely. Could the TRV have failed internally? I'm doubtful its got crap in the system as it was completely replaced only 4 years ago and has had Fernox inhibitor and a magnet filter fitted, flushed and cleaned yearly and Fernox checked and redosed. Water in the system is nice and clean if I've ever do work on it like remove rads etc.
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Turn both valves off and open bleed screw, a little water will come out and then stop. At that point close the bleed valve and open the TRV. Then open the bleed valve and water should flow out fairly strongly if water is passing through the TRV. No strong water flow means TRV is internally stuck closed ,or there is a blockage.
Before closing the lockshield valve ,count how many turns / part turns, it takes to close ,so you can return it to its original position.
The pin under the TRV head ( on the brass body) may be stuck in closed position.
If either pipe cold or luke warm, gentle tap on the pin might free it and restore circulation
The pin moves freely up and down (although you need something hard to push it as it digs into your figure)
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If the pin pushes in and then pushes out without your help, the; issue with circulation as per Terry post
If i crack the bleed nipple water ****es out so it's getting water from some where maybe the valve on the other side is stuck?
If i crack the bleed nipple water ****es out so it's getting water from some where maybe the valve on the other side is stuck?
Did you follow the method I outlined earlier ? If so ,at what point did water **** out from the bleed valve ,was it while lockshield was fully closed and TRV open ?
Ok so I've found the lock shield valve was only open about 1/8th of a turn. Opened it up to 1/4 and the rad is getting nice and warm. Its a fair way from the boiler so id expect it to be a bit more open that that I'll have too check the balancing record to see what it should be set at. Can't seem to figure it out, the system was installed new and balanced about 3 years ago, and this radiator worked fine up until about a week ago. Its behind a computer desk with the plastic cover on the valve, it's just taken me and hour to move everything off the desk and lift it out the way to get to the lock shield valve, so I know its not be touched as there's dust marks around things as I move them. Could a bit of crud got in the valve opening and restricted the flow. I fully opened and closed the lock shield a few times before setting it back to an 1/8th of a turn open and the rad went cold after a while so I've opened it back to a 1/4. I'll have to re check the all the radiators now and re balance them. oh joy!

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