TRV Sticking constantly

[browneye23]

I moved in to a new bungalow a few weeks ago.
I put my heating on for the first time at the weekend I noticed that two radiators were not getting hot.
My first thought the TRV’s must be sticking as the system is not even a year old.
I removed the head of the Thermostatic Radiator Valves and pressed down on the pin with the flat part of a screwdriver hoping to un-stick them.
After a few hours of trying a few things, turning all other rads off and isolating those two rads so all water flowing to them.
Nothing seemed to happen.
I called a plumber who told me actually it was the TRV’s stuck and came round.
He got a hammer and ‘bounced’ it up and down on the pin and after about 30mins he got them all to work.
The day after when the heating came on, these two radiators were again cold… to my obvious frustration.
As an interested party I watched how he did this and had a go myself
When I tried to do this I have had no luck in getting them to release, last thing I want is to have to pay a plumber every time the heating needs to come on!
Does anyone have any tips on how to release particularly sticky TRV’s?

 

[JohnD]

stop fiddling with the TRVs and turn off your hot radiators. Do the cold ones now heat up? If so, post back here as it is caused a different problem.

I strongly advise you not to use a hammer as you will damage them.

 

[browneye23]

When all the other radiators were off these two did not heat up.
The pipes though on these two rads did get warmer.

I am not smashing the pin with the hammer, I am using it to bounce it up and down to free it up.

I have put some WD40 into the pin hole hoping these might free them up a bit.

 

[JohnD]

is the pin now sticking up? If you leave the thermstatic heads off, and the pins sticking up, the valve is likely to be open, and stay that way.

When you bleed the radiators, does water squirt out forcefully? What colour is it?

Turn off every other radiator in the house, and see if these warm up. If not, feel the pipes going in and out of the boiler, so see which is teh feed and which is the return, and how hot they both are. Also feel the circulating pump, and see if it is the same temp as the pipes, or hotter.

Are the cold radiators upstairs or down? When did they last work properly?

some photos would help

 

[browneye23]

Pins are sticking up and they are what I describe as spongy (going up and down if I push down with my thumb or flat side of a screwdriver)

Radiator water is clear, and they have a decent pressure when opened.

I live in a bungalow so no upstairs.

All other rads in perfect working order across the house.

 

[JohnD]

OK. the question is, if you turn off every other radiator in the house, do these rads warm up? Feel the flow and return pipes at the boiler, and at the pump, and see how hot they are (the flow should be "too hot to hold" and the return should be "too hot to hold for long")

how far are these cold rads from the boiler, and when did they last work properly?

Photos of the TRVs would help. If you can't do that, tell us make and age. Are the pipes to the TRV 15mm or what? The pins should spring up quite hard when you release them. Try one of the rads that is working properly and see if they feel different. Always set the head to its highest setting before you fix it back on.

 

[browneye23]

If all other rads are turned off no these do not work.
The pipes below get warm but not too hot to hold (when all other rads off)
The pipes were cold when the engineer was tapping the pin and then all off a sudden they came on.
All other pins seem to be exactly the same as the ‘stuck ones’
The engineer said to me, you can hear the difference when they come unstuck.
Also he closed the valve off at the other end.
I have unstuck TRV’s in my old house these were much easier to release.

Last time everything was working properly was after the engineer left, next time the heating was switched on these two did not work and went back to how they were before.

These two rads are the approx 2m and 3m from the boiler (these are the closest two).

Pipe size is 15mm copper.
The make of the TRV – I can’t remember something is telling me it begins with a W and has a 4 on it (I am at work) so will check later. It’s not a brand I recognise ie Pegler, Honeywell Danfos
The system is no older than a year.

 

[kevplumb]

Also he closed the valve off at the other end.

and did he open it again

 

[browneye23]

Yes, they are open!!!

 

[JohnD]

OK.

Take the covers off the lockshield valves at the other end of each radiator, and check that they are open a few turns.

Leave the thermostatic heads off the jammed ones, if they ever free off, the heads might push the pins down and make them jam again. If necessary you can reduce the flow using the lockshield.

It sounds like your old valves are knackered and need changing. If you are fond of DIY plumbing it is not very difficult, except that (unless you can buy a very similar valve) the old one will be a slightly different size and you will have to cut the old olive off the pipe. It is much more difficult if the pipes come up through a concrete floor and have no play in them.

If you are buying new valves, you may as well change the lockshield at the same time, and (if you do not already have a drain cock) you can fit a lockshield with drain incorporated.

Some good makes of valve are Danfoss and Drayton, though Drayton are overpriced as they used to be very fashionable and stylish.

If you have to drain down to change the valves, you might consider changing them all as they are probably all equally old. It is not a difficult job, but is labour intensive, so will cost hundreds if you have to pay someone else to do it. If you do it yourself it might take you a weekend but might cost only £15 per rad.

If you have to drain down, this is also a good time to give the system a chemical clean, and add fresh inhibitor on final refill. Cleaning it will also reduce the risk of dirt and sediment clogging the pipes or wearing out the pomp or making more valves jam. Again it is a cheap job if you DIY. You want to get it done before the weather turns really cold as the chances are your heating will be out of action for a couple of days. I am a competent DIYer and it took me more than a day's work, though I speeded up with practice and having all the tools and materials to hand.

 

[browneye23]

Thanks for your help.
Seems as though the pins are permanently stuck.
I have confidence that the system is in very good working order as when the rads worked the once time everything was fine and all other rads are in top shape
I have changed TRV’s before by draining down a system so this seems like the best idea and change them all.
The pipes are easily accessible so I don’t think changing them will cause too many problems.

 

[browneye23]

Well turns out my pump was causing the problem!
It overheated last night and has broken down.
Great diagnosis in the first place by the engineer that the TRV’s were sticking!

Currently I have a DAB pump so I am going to do a like for like replacement.
I have been told to get a Grundfos, but I know that in my industry (borehole pumps and motors) Grundfos manufacturer for DAB !
The cheaper alternative is a Myson – but I don’t know anything about these.

 

[MJN]

Well turns out my pump was causing the problem!

How do you know that given you've yet to replace it?

Great diagnosis in the first place by the engineer that the TRV’s were sticking!

Has it occured to you that you might have two problems...? I'm not saying you necessarilly have but don't be too quick to diss your plumber, particularly if you called him in to 'fix the sticking TRVs' and the pump was showing no obvious signs of impending failure.

Mathew

 

[browneye23]

I can tell you I do not have two problems.

I have a valve next to (about 30cm away) from my pump.
I turn this clockwise the two cold rads come on the rest go off.
I turn it anti clockwise these two rads go off and the rest come on.
This indicates to me that the TRV's are certainly not stuck!

The pump was making a noise and now has caused the boiler to cut out due to over heating.

My diagnosis is that the pump is broken and needs replacing as it certainly isnt pumping any water around the system anymore.

A phone call to the plumber who did my job said I that this was probably was causing the problem based on all the information.

 

[MJN]

Apologies. I must've missed your earlier mention of being able to get the problem radiators to heat up by closing off the pump valves. As you say, this confirms that the TRVs are not stuck.

Mathew