One cold upstairs radiator - why?

[beedj]

I have one upstairs rad which is stone cold - rest of system is working fine. I've checked the obvious - ie that the thermostatic valve (TCV) is open, and I've removed the TCV to make sure the small brass pin isn't stuck down - it's not, it's moving smoothly. I've also treid venting (bleeding) it - no air - cold water immediately flows from the valve.

The system hasn't been touched for over a year when we had some minor building work done, and it's always worked fine before and since then

Suggestions welcome on how I might get it going again ? - I can only guess it is some sort of airlock ?

[matsmith]

Was the rad removed during these building works?

You have checked the thermostatic valve, have you also checked that the valve on the other end of the rad is open?

[Herbs]

If those other suggestions don't work then I suggest turning down all the other rads and see if that one then comes to life. It could be your system is unbalanced if it hasn't been used for over a year and had bits removed/replaced.

Mine did similar on my new property which was a mixture of an airlock and unbalanced (sort one out and the other would appear)

i'm not an expert by any stretch but will only take you 10 minutes to check and hopefully someone with more experience will be along in the mean time;)

good luck.

[Deva Link]

With the system off and all the other rad valves open shut one of the valves on the rad and bleed half a bucket of water out of it, then shut the valve and open the other end and do the same. Ideally take the bleed screw out so there's a good flow - don't worry about getting the screw back in, shut off the valve and the flow will stop.

Is the system gravity fed or pressurised? If it's pressurised you'll have to keep the pressure up - easier if someone is helping you.

[louiebaby]

matsmith said:

Was the rad removed during these building works?

You have checked the thermostatic valve, have you also checked that the valve on the other end of the rad is open?

This would be my best guess. I was going to post it, but was beaten.

[/adding nothing to the subject]

[VxDuncan]

I have this at my house and still haven't fully gotten to the bottom of it. At one point I had three rads that were stone cold. Took two of them off and ran shed loads of cold water through them. Also flushed the pipework through by connecting a hose / shower hose to the TRW and LS outputs darining in a bucket (one at a time). Got SOOO much crap out of just the pipe work. Quite good fun, water is clear for ages, them you get a couple of seconds of black water, then clean again.

Worked a lot better, however I'm convinced one of the radiators downstairs is in series with those upstairs, so if you reduce the flow through it (it's always hot) or the TRV kicks in, it's colder upstairs. Not good....

[beedj]

matsmith said:

Was the rad removed during these building works?

You have checked the thermostatic valve, have you also checked that the valve on the other end of the rad is open?

No this rad wasn't touched; the building works are probably a red herring as the full system - including this rad - have worked fine for 18 months since work complete. It was definitely hot a week ago, then 2 days ago I noticed it was cold. I hadn't checked the valve on the other side of the cold rad as it is underneath a plastic cover which is screwed on and nobody could have touched it. However I've now checked and it is open (part way - ie it will turn in and out - probably as it's been set at balanced position I guess). I tried opening to max but this made no difference

[beedj]

Deva Link said:

With the system off and all the other rad valves open shut one of the valves on the rad and bleed half a bucket of water out of it, then shut the valve and open the other end and do the same. Ideally take the bleed screw out so there's a good flow - don't worry about getting the screw back in, shut off the valve and the flow will stop.

Is the system gravity fed or pressurised? If it's pressurised you'll have to keep the pressure up - easier if someone is helping you.

Thanks I'll try this; the system is pressurised. Am I right in thinking when you say "shut off the valve and the flow will stop" you mean the TCV ? ... whereas your other mentions of valve mean the vent/bleed valve?

[Deva Link]

beedj said:

Deva Link said:

With the system off and all the other rad valves open shut one of the valves on the rad and bleed half a bucket of water out of it, then shut the valve and open the other end and do the same. Ideally take the bleed screw out so there's a good flow - don't worry about getting the screw back in, shut off the valve and the flow will stop.

Is the system gravity fed or pressurised? If it's pressurised you'll have to keep the pressure up - easier if someone is helping you.

Thanks I'll try this; the system is pressurised. Am I right in thinking when you say "shut off the valve and the flow will stop" you mean the TCV ? ... whereas your other mentions of valve mean the vent/bleed valve?

Valve means valve - either "TCV" (more usually called TRV - thermostatic radiator valve) or the other end, the lock shield valve.

The water comes out of the bleed screw hole. Even with the screw out, if you shut off the rad valves, water will stop spurting out (as there's no pressure to push it out).

If all the other rads are open and you find water doesn't flow out of the bleed hole with one or other of the valves open then you've got a blockage somewhere.

Be aware that if you do this, the water will likely be extremely dirty - don't get it on the wall, carpets, curtains etc or you'll be most unpopular.

[beedj]

Understand - thanks - water is definitely flowing from bleed screw when I open it half-a-turn, so there's some pressure there & suggests no blockage. I'll need to rig something up to protect carpet etc to let more water flow through as you suggested.... will have a go this evening.

Thanks again

[B17NNS]

Turn off all other rads in the house using the TRV's. The water only has one option then - to go through the cold rad.

The cold rad should (hopefully) now warm up.

Turn on other rads and report back.

[Deva Link]

B17NNS said:

Turn off all other rads in the house using the TRV's. The water only has one option then - to go through the cold rad.

The cold rad should (hopefully) now warm up.

Turn on other rads and report back.

Someone already suggested that and I would do that first, although as it's a sealed system the water will probably just route through the bypass if there's any kind of blockage.

[matsmith]

beedj said:

matsmith said:

Was the rad removed during these building works?

You have checked the thermostatic valve, have you also checked that the valve on the other end of the rad is open?

No this rad wasn't touched; the building works are probably a red herring as the full system - including this rad - have worked fine for 18 months since work complete. It was definitely hot a week ago, then 2 days ago I noticed it was cold. I hadn't checked the valve on the other side of the cold rad as it is underneath a plastic cover which is screwed on and nobody could have touched it. However I've now checked and it is open (part way - ie it will turn in and out - probably as it's been set at balanced position I guess). I tried opening to max but this made no difference

I only asked if it had been removed because I have caught less conscientious folk blocking flow & return pipes in a new build in the past.

As it's been working up until recently try as has been said; bleed the rad until warm water comes out, and/or turn off the other rads in the house and see if that forces the water to that rad.

It sounds as though the return pipe might be blocked. It's just curious how it was working a week ago! Have you noticed any loss of pressure in the system?

[Wings]

I had the same today at a rented property, tried to both balance and bleed the radiators, checked and adjusted the pump settings, that gave an indication that the propellor wassticking, so fitted new pump and the cold rads got hot.

[andy43]

This radiator isn't in Simpo Two's bedroom is it?

[Festive Ferg]

Depending on pipe runs it's certainly possible that you have an air-lock.
I'd do as suggested and push all the pump's flow (not pressure..) through one radiator. This may involve closing a bypass valve and certainly make sure you don't have 'hot water' selected on the programmer.

[beedj]

I've tried routines as above and no joy as yet ....

The lock-shield valve also has a drain-off valve attached (on the radiator side of lock-shield valve).

If I open the TRV, then open the drain-off valve (on other side of rad), water flows continuously from the drain-off valve (regardless of whether lock-shield valve is open or closed), and I start to get some warm water at the TRV. If I close the TRV then the water stops flowing from drain-off valve. I think this proves the TRV is okay ?

If I close the TRV, and open the lock-shield valve fully (I counted the turns so I know where original balanced position was), then nothing flows from the drain off valve when I open it - is that as it should be ?

No loss of pressure under normal operation by the way (other than when I've been messing about opening valves trying to fix this problem). Water running from valves is very clean

Does this info help ?!

Edited by beedj on Tuesday 21st December 21:27

[Festive Ferg]

The pipe attached to the lockshield end sounds blocked. Either with debris or, more likely, air... You've had the full pump flow on that radiator?? Strange.

[beedj]

Yes (although I didn't close a bypass valve - no idea where this is or what it looks like ?!) - I'll try again though - how long should I expect to have to leave full flow on that rad ?

I had all the other rads turned off via TRVs while I was messing about, but have opened them again at the moment - need house to warm up before I try again!

Edited by beedj on Tuesday 21st December 22:12

[Deva Link]

beedj said:

If I close the TRV, and open the lock-shield valve fully (I counted the turns so I know where original balanced position was), then nothing flows from the drain off valve when I open it - is that as it should be ?

This is probably a stupid point, but just in case! - Nothing from the drainoff when it's opened implies the radiator is empty. You did refill it, didn't you?


What model of boiler have you got - I wonder if there's something in the boiler arrangement that stops water coming out when you open the lockshield?

Where you trying it with the system running?

Do you know the route this pipe (from the lockshield) takes to connect to the rest of the system - it couldn't possibly be frozen somewhere, could it?