Can a TRV fail with its sprung pin 'out'?

One of our radiators has stopped working completely; ie not a trace of warmth when the CH is on. First port of call was an investigation of the valve, suspecting that its pin might be stuck down; however it definitely isn't, and it's currently in the fully 'out' position with the valve head removed, and the rad's still in Witches' Tit mode.
So - is it possible the valve still needs replacing? Or am I looking at a blockage (or, unlikely, an airlock) somewhere?
David
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The jumper (that the pin pushes down) can stick to the valve seat. There's no solid link between pin and jumper. I usually give the valve body a sharp tap with a hammer/spanner/whatever comes to hand and that seems to free it up.
Tim
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Lobster wrote:

currently working on 4 new builds and had this problem with one rad in each house - the same one in each house for some reason - all the rest were glowing and this one wouldn't get warm. Left heating on and turned all other rads off and it got hot, then went around and turned all other rads back on and now they all work fine, we did get a bit of air out of the one on the third floor so it was probably an airlock.
The cold rad was on the ground floor only 5m from the boiler, yet the 'loft' one got heated up fairly quickly
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On Thu, 8 Nov 2012 20:28:38 -0000, Phil L wrote:

Sounds as if gravity is making the circulation happen as much if nor more so than the pump... Was the ground floor rad on long (FSVO long) from the main flow and return pipe work?
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Dave.




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Dave Liquorice wrote:

No, the pipe run was a metre up from boiler, about 3m across a ceiling and 2.5m down a wall, not much different from the other two downstairs ones, then there's 3 on the middle floor and one in the loft room.
Boilers are glow worms, 26k I think.
They all seem to be fine now, I've a feeling there was a 'U' in the pipe to this rad - it's all done in plastic and it was coiled, so it could be an undulation where they were drilled through the joists
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On Thu, 8 Nov 2012 21:12:17 -0000, Phil L wrote:

What you describe is quite a large inverted U. Plenty of scope to trap air, particulary if the pipe work runs ever so slightly up from the main flow return runs.
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Dave.




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Lobster wrote:

This is what I wrote a long time ago:
I have attacked mine several times in the following way, without draining the system, and no more than a dribble of leakage.
Having unscrewed the dome, prod the pin which protrudes from the valve a few times. Mild jams can be cleared this way.
If it is still stuck, first get some old cloths or towels to catch any spillage. Remove the circlip and lift out the plate through which the pin passes. Beneath is a rubber diaphragm, which may or may not come with it. Remove it, taking care not to tear it. Water may start to well up in the valve body. Insert a screwdriver into the body, of a suitable size so that it is a fairly tight fit. A mixture of jabs and twists with the screwdriver should result in it freeing the mechanism. You will feel the spring release, and the valve will be free to move vertically.
Now you have to get things back together. Replace the rubber diaphragm, replace the plate with pin protruding through. Now comes the hard part - get the circlip back. Some of my valves have had this done so many times that I really don't want to disturb them again.
If this still does not work, then you will have to drain down, and get right into the valve to persuade the parts to move freely.
I had all the valves replaced a few years ago, when I had a new boiler, fresh inhibitor was added, and they haven't needed any attention.
Chris
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Chris J Dixon Nottingham UK
snipped-for-privacy@cdixon.me.uk
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Or, gie it a dunt wi' a hammer. ;-)
Tim
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On 09/11/2012 09:19, Tim+ wrote:

Thanks for this. Don't you at least have to depressurise the system to do this? As in, when this circlip comes out won't the system otherwise 'self-depressurise' rather rapidly at that point?

Thanks for the tip - I attempted a good old 'dunt'ing yesterday, but alas to no avail.
(At least this is the spare room rad - normally set to 'off' anyway; which is probably the root of the problem...)
David
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rLobster wrote:

At the time my system was vented, so just the static head to cope with. Although there was some water seepage, very little actually escaped.
For a pressurised system, you may well be right.
Chris
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On 08/11/2012 19:40, Lobster wrote:

If the pin springs back up when you push it down and then release it, the valve is probably ok. You can check that it's passing water by fully shutting[1] the lockshield valve and then opening the bleed screw. If water squirts out, water must be flowing through the valve (unless the lockshield is duff and not shutting fully - but let's assume that the lockshield is ok). If air comes out, keep it coming until water starts to come out (and then top up the system to the correct pressure). For completeness, close the TRV fully (preferably with a decorating cap), open the lockshield and re-bleed - to ensure that that side of the circuit is working.
Having proved that water is flowing through *both* valves, if the rad still doesn't get hot, you've probably got an air lock. The usual trick here is to turn off all the other rads, turn the pump up to max speed - if adjustable - and run the system for a bit. That should clear any air lock, and the rad should get hot. After that, it should continue to work ok.
[1] Count how many turns are needed to close it, so that you can restore it to the same position (assuming that the system has ever been balanced!
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Cheers,
Roger
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Roger Mills wrote:

Um, no. I've had the jumper stick in one of my radiator valves many times when it's been turned off over summer. A good dunt to the valve side with a hammer has always freed it off.
Tim
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On 09/11/2012 14:24, Roger Mills wrote:

As I finally got round to sorting the above out at the weekend (during a system drain-down necessitated by installing a new rad elsewhere in the house) i thought I'd just report back (always good to hear the outcome, innit?). Thanks Roger for the sensible how-to-do-it.
Upon investigation I found the lockshield valve was completely shut off, which would of course account for the completely cold radiator. WTF? Then - lightbulb moment - I suddenly remembered that *last* winter I had a problem with this rad (which is in a little-used spare room) not being possible to turn *off*: ie with the TRV set to minimum the rad was still warming up and keeping the empty spare room warm all winter. So I shut down the lockshield valve and made a mental note to sort it out come the summer. HTF did I just completely forget that? Well scary. :( :(
Fortunately the grey cells are still up to swapping out a failed TRV, which I duly sorted out...
David
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On Thu, 13 Dec 2012 08:08:25 +0000, Lobster

"Mental note", yep, been there, too! I'm 66 and now have to make written notes if I want to remember anything important. Pi**es me off, but if I try to remember important stuff, I just forget. And yet I can cast my mind back to age eight in Hastings in the 1950s and remember loads of details of my everyday life.
By the way, if you start jotting down "reminders", always make a mental note to where those reminders are, else you'll never find 'em again!
MM
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On 14/12/2012 07:03, MM wrote:

Do you ever watch that Foyles War?

--
Dave - The Medway Handyman www.medwayhandyman.co.uk

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On 14/12/2012 08:22, The Medway Handyman wrote:

Possibly. Can't remember...
David
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Had three of they recently differing properties. All the same a gentle tapping and tweak and they work OK again ...

Yep thats ageing;(..
Ought to be a law 'agin it;!//

Like all those bloody passwords U have to remember..
Still I've now simplified doG.............;)
Which they say is rather good one;)..

--
Tony Sayer


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I just bought a whiteboard for my study for this very reason.
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Today is Pungenday, the 56th day of The Aftermath in the YOLD 3178
"I saw Lon Cheney walking with the Queen."
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