Single Radiator issue

[Neil Curtis]

Wonder if anyone can help?

One of my radiators is cold all over.
I've checked the thermostatic valve and its working and moving up and down.
The pipe leading to the valve is hot and the small stretch of pipe going into the radiator is hot....but the radiator is still cold.

thanks

 

[Ric2013]

If the small stretch of pipe leading to the rad is hot, then it follows that there is probably some flow to it. Could, however, be a convection current within a single pipe if the pipe runs up to the radiator from below?

I have seen TRVs that seem to be working and when you take the head off the sprung pin appears to come up and down but the valve still isn't actually working properly.

Question 1. When you say the TRV goes up and down, do you just mean the head moves, or have you had the head off and can confirm that the pin on the valve below can be depressed and springs back when released?

Question 2. Did this radiator used to work, and has anything been altered since it was last working?

 

[Best]

Assuming the radiator isn't full of air, then it could be one of several things.
Your thermostatic rad valve could be seized inside - (the outer pin moving doesn't mean the valve is working)
Also make sure the other valve is turned partially on, (anti clockwise) to test.
Other than that, you could have a blockage in a pipe or the rad is full of gunge.

 

[Ric2013]

Plus one to that, sometimes the outer pin moves but the valve stays shut. If the OP knows everything used to work okay, I'd be tempted to open the valve fully or remove the head and whack the side of the valve body a few times with a spanner in a bid to free things off. Though the valve probably needs replacing and will seize again.

 

[Best]

Yes, maybe tap the pin with a hammer a few times might sometimes work. But even if that was successful a new valve is needed eventually.

 

[Neil Curtis]

If the small stretch of pipe leading to the rad is hot, then it follows that there is probably some flow to it. Could, however, be a convection current within a single pipe if the pipe runs up to the radiator from below?

I have seen TRVs that seem to be working and when you take the head off the sprung pin appears to come up and down but the valve still isn't actually working properly.

Question 1. When you say the TRV goes up and down, do you just mean the head moves, or have you had the head off and can confirm that the pin on the valve below can be depressed and springs back when released?

Question 2. Did this radiator used to work, and has anything been altered since it was last working?

Thanks
Yes, I've had the head off and the pin will move - albeit, not smoothly.
It used to work, but it stopped a while back; just getting on to fixing it.

Thanks again.

 

[Neil Curtis]

Assuming the radiator isn't full of air, then it could be one of several things.
Your thermostatic rad valve could be seized inside - (the outer pin moving doesn't mean the valve is working)
Also make sure the other valve is turned partially on, (anti clockwise) to test.
Other than that, you could have a blockage in a pipe or the rad is full of gunge.

thanks.
The other valve - to the left of the thermostatic - could you tell me the purpose of this one? How far do I turn this one; fully until it stops?

thanks again

 

[Ric2013]

The other valve - to the left of the thermostatic - could you tell me the purpose of this one?

If it was working before you can probably leave this one. Its purpose is to regulate the flow through the radiator to ensure each radiator receives as much hot water as it needs and no more. The process is called 'balancing radiators'. In practice, not all systems are balanced properly though.

 

[Best]

thanks.
The other valve - to the left of the thermostatic - could you tell me the purpose of this one? How far do I turn this one; fully until it stops?

thanks again

As Ric2013 said, it is for balancing the radiator flow. Also is for isolating the radiator for removing it etc.
The reason I suggested opening (anti-clockwise) a turn is sometimes a lockshield valve will be barely open and any crud that might be in some systems will block the valve.