Cold Radiator

[Baxman]

I have a cold radiator in our Garden Room. This room was a garage conversion and I suspect that the offending radiator is the last one to be served with hot water - despite fact it is quite close to the boiler.

There were two rads in the room that were cold but I seem to have persuaded one to work by flushing it, refilling and bleeding. This does not seem to have worked on the other.

I have switched off all other rads in the house and left only the offending rad on. It still didn't heat up so I think I have ruled out balance problem.

The rad filled up ok when I put it back on after flushing. I then switched the system on full blast. The pipe at the base of the rad heated up (v hot) but no water seemed to be getting into the actual rad - v confusing as I managed to fill it through this valve.

I suspect the rads in this room were part of previous owners DIY (talent somewhat patchy!), could he have fitted things the wrong way around? Any other suggestions ? I am going to buy a new thermostatic valve to see if that fixes it.

Apologies for length of e-mail but hopefully more info will help u experts narrow down my prob.

Cheers
Baxman

 

[Bahco]

Turn off valves supplying this rad (after draining this drop )and then remove the rad from the wall.
Refill system and open 1 valve to see if you have a blockage. If you get a good flow do the other valve. This may push out any sludge.
If no flow you have a blockage which will need flushing out.
Might be worth renewing valves if they are old while you are at it

 

[Baxman]

Now that you have said this something has twigged with me. When I opened the 'hot' valve the rad did not seem to fill (with the bleed valve open). When I then opened the cold valve the rad filled. Can you tell me if the rad would effectively back fill on opening the 'cold' valve or if water only flows one way in these systems. Intuitively if I open the bleed valve and am putting water into the system then it can back fill and this would point me towards the fact that my hot valve is blocked and the lukewarm/cold rad is being caused by slight backfilling.

If the above is the case can I change the hot thermostatic valve without draining the whole system. If so how do I do it.

Thanks I think you have already set me off on the right track

Baxman

 

[Bahco]

If the above is the case can I change the hot thermostatic valve without draining the whole system. If so how do I do it.

Baxman

I Wasn't aware that you already had a TRV fitted.
It probably has the pin sticking. Try tapping gently to free and then turn up to highest setting.
If old tho renew

 

[kevplumb]

if you dont want to drain the system you can freeze the water in the pipe
id go with bahco and look for a blockage
good tip about the valves ill remember that

 

[Baxman]

Managed to solve probs but had sent everyone (myself included!) off in the wrong direction!

It was a balance problem. When I refilled the radiator after flushing it I didn't open the lockshield valve (which the previous owner had fully closed). The rad filled by virtue of the fact that bleed valve was open.

When I checked for balance issue I closed all other rads down but obviously no hot water got into the offending rad.

I then had another back to basics session last week and went round balancing my whole system. Low and behold when I fully opened the lockshield valve the rad began to heat up (still not the hottest radiator but as it is the last that is understandable).

Thanks for all the pointers

 

[ChrisR]

We professionals NEVER do anything like that

 

[kevplumb]

speak for yourself mate