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[Nickbat]

...oh, and it was professionally fitted system. No DIY involved.

[Boiler Man]

Sound very likley that the thermostatic rad valve has stuck our gone faulty on that rad. They can stick over the summer when they are closed a lot because its warm or could be in your case that because the fire is on so much it has been closed almost all the time. The rubber seat sticks to th inlet orifice.

A quick test to be sure it isnt an air lock. Close all your other radiators by turning the thermostatic valve down to minimum. Leave the faulty one fully open or take the head sensor off. Run the system Leave it about 10 mins or so and if your faulty rad gets hot it could be an air lock or balancing required.

If it doesnt get hot with all the others off then it is more than likley the thermostatic valve is stuck or faulty. Remove the head sensor of the vave body. Then try tapping the side of the valve body with a medium size spanner or adjustables to try and free the rubber seating inside the valve, you could even try tapping the pin on the top, but be very carefull, if you hit it to hard you can drive the pin straight though and you have a leak.

If this doesnt work, I think you need to replace the valve complete. Let me know how you go on or PM me.

[Boiler Man]

Oh ... and make sure your system is topped up to about 1 Bar or no1

[Nickbat]

Sound very likley that the thermostatic rad valve has stuck our gone faulty on that rad. They can stick over the summer when they are closed a lot because its warm or could be in your case that because the fire is on so much it has been closed almost all the time. The rubber seat sticks to th inlet orifice.

A quick test to be sure it isnt an air lock. Close all your other radiators by turning the thermostatic valve down to minimum. Leave the faulty one fully open or take the head sensor off. Run the system Leave it about 10 mins or so and if your faulty rad gets hot it could be an air lock or balancing required.

If it doesnt get hot with all the others off then it is more than likley the thermostatic valve is stuck or faulty. Remove the head sensor of the vave body. Then try tapping the side of the valve body with a medium size spanner or adjustables to try and free the rubber seating inside the valve, you could even try tapping the pin on the top, but be very carefull, if you hit it to hard you can drive the pin straight though and you have a leak.

If this doesnt work, I think you need to replace the valve complete. Let me know how you go on or PM me.

Thanks BM, I'll give that a go  

By the way, you mentioned balancing. How do you balance a radiator?

[supermop]

I'd say try bleeding the rad, and change the valve.

What I'd do however, is nothing... cos I'm too lazy

[Andy B]

......
By the way, you mentioned balancing. How do you balance a radiator?

It's the system you're balancing, not the individual rad. The water flow will take the path of least resistance, so if the water can go through an open valve up stairs for example it'll not bother with a rad down stairs if can avoid it. If you close off the rads up stairs a little you're increasing the available flow for the other rads.

[Boiler Man]

Try the quick test I suggested first, in effect you would be doing an extreem balance by forcing the circulation to go only to the faulty rad, when you shut the others down and by the way make sure the other valve, at the opposite end to the thermostatic (the lock shield valve ) on the poor rad is fully open.

If you do the test - shutting all the others down with the bad one fully open and that rad doesnt get hot. Balancing wont make the slightest differance.

 

[Nickbat]

Try the quick test I suggested first, in effect you would be doing an extreem balance by forcing the circulation to go only to the faulty rad, when you shut the others down and by the way make sure the other valve, at the opposite end to the thermostatic (the lock shield valve ) on the poor rad is fully open.

If you do the test - shutting all the others down with the bad one fully open and that rad doesnt get hot. Balancing wont make the slightest differance.

 

Tried the quick test and the rad failed to get hot, so I'll now try loosening the seal in the thermostatic valve with a few gentle knocks of a spanner (got my 2-year old here to help me!  )

I'll report back soon.

[Nickbat]

Well, the pin in the thermostat slides in and out fine, although that does not mean the seal in the valve is moving. On the other side of the rad, the lock shield valve is fully open and the body of the valve is too hot to hold for any length of time. Rad still not very warm. Tried re-bleeing it, but to no avail.

Think it's time for a new thermostat valve.

[Boiler Man]

Had all the other rads cooled down a bit, when you tested. This just proves that there is no circulation through them even thou they are turned off?

Yep, your right the pin sliding in and out doesnt mean the seat is free, you could try draining system, taking it off and having a look inside, but by the time you have done that you may as well replace it.

Try and get the same make as the old one, you have more chance of it matching up with the old valves unions, makes things a bit easier. Plus make sure your new one is Bi-directional. Most are these days but check. The old ones could only be fitted to the flow pipe, by the sounds of it your thermostatic is on the return, so it should be bi-directional or two way.

[Taxi_Driver]

Quick question and i expect boilerman will know.....

Does the pin move easily in and out?.....just when the pins on my stats get i can free them up.....but they are normally quite stiff to push in.....i assume i am pushing against the water....then when i release them the pins pop out slowly on their own....again assuming the water pressure is doing this .

Does this happen on yours Nick?

[Nickbat]

Quick question and i expect boilerman will know.....

Does the pin move easily in and out?.....just when the pins on my stats get i can free them up.....but they are normally quite stiff to push in.....i assume i am pushing against the water....then when i release them the pins pop out slowly on their own....again assuming the water pressure is doing this .

Does this happen on yours Nick?

Well, TD, I only got the pin to move in and out using a pair of long-nosed pliers. But, I think that as you rightly say, the water pressure pushes the pin out (maximum setting on the thermostat) and the action of turning the stat down pushes the pin in and reduces the flow .

Two further questions for BM:
1) How much am I looking at for a new stat?
and
2) How often should I add Fernox to the system? (Been doing a bit of bleeding and topping up lately. Last done a couple of years back)

[Nickbat]

Had all the other rads cooled down a bit, when you tested. This just proves that there is no circulation through them even thou they are turned off?

Yep, your right the pin sliding in and out doesnt mean the seat is free, you could try draining system, taking it off and having a look inside, but by the time you have done that you may as well replace it.

Try and get the same make as the old one, you have more chance of it matching up with the old valves unions, makes things a bit easier. Plus make sure your new one is Bi-directional. Most are these days but check. The old ones could only be fitted to the flow pipe, by the sounds of it your thermostatic is on the return, so it should be bi-directional or two way.

Thanks Boiler Man. Your a star. I'll get a Bi-directional one.

I posted a reply to Taxi Driver and a supplementary question for you (well, two actually   before I posted this Thank You note. Sorry about confusing you!

[Boiler Man]

Hi sorry for the delays in answering, as you can imagine it's my busy time of year, so away from the comp' quite a bit.

Your looking at between 12 and 20 quid, depends on the quality. Dont go for the cheapest as usual it's not always the best policy. As I mentioned do your best to ID the same make.

and use a smear of jointing compound like hawk white or simaler only on the olives (not as some people do on the thread) the threads are just there to tighten the olive on to the valve face.

Good luck

By all means PM me if you have a problem. or pm me for my phone number I'm a bit far away for a call out.

[Nickbat]

Cheers, BM