One radiator refuses to heat up

[Ravel]

I have an irritating condition with my CH system in that no matter what I do this one radiator will not work, and when all the other six are hot it remains cold.

I have read loads of posts from a search and tried pretty well all the suggested cures with no success.

The boiler is a Worcester CDi30 which is working fine, and the problem radiator is downstairs below the master bedroom with it's feed and return in corner ducting which goes up to the bedroom and under the floorboards along the full room length towards the rear kitchen where the boiler is located.

Much to my wifes displeasure I have rolled back the carpet and lifted the floorboards and have identified the 15mm feed pipe which just like downstairs is cold, and half way along the room a T feeds the bedroom rad with microbore and at that junction the pipe is hot with the room rad also working normally.

As I run my hand along the 15mm feed pipe in the direction of the downstairs drop down it gradually becomes cooler until finaly cold, and that change is happening in about 2 mtrs of pipe.

I can only think it's a very stuborn air lock or a severe blockage, and I've bled about 4 pints out of the rad top to no avail.

Any ideas please.

Regards Ravel

 

[namsag]

Close of both valves at offending rad pressurise boiler to 2 bar then undo them from rad and open one a time to see what flow you get out of them.

 

[bennyxf1]

trv pin stuck in?

 

[Ravel]

Close of both valves at offending rad pressurise boiler to 2 bar then undo them from rad and open one a time to see what flow you get out of them.

Hello namsag, thanks for your suggestion, and I will try it tomorrow morning.

Regards Ravel.

 

[Ravel]

trv pin stuck in?

Thanks for your post, but that is one of the first things I tried, and the pin springs out quickly when pushed in with a flat object.

Regards Ravel.

 

[namsag]

If this rad has alway played up..One thing you could check seeing as you have had boards up.. check that the flow and return to this rad are not teed into the same pipe

 

[Ravel]

If this rad has alway played up..One thing you could check seeing as you have had boards up.. check that the flow and return to this rad are not teed into the same pipe

Hello again namsag, the flow and return pipes run along side each other, and it's easy to see the setup is correct, and the system did not have this one rad problem until the recent fitting of the new boiler.

Regards Ravel.

 

[Ravel]

Close of both valves at offending rad pressurise boiler to 2 bar then undo them from rad and open one a time to see what flow you get out of them.

Hello namsag, today I'm a happy man because by using your procedure the problem is cured.

Firstly after closing both ends of the rad I started to loosen the nut holding the microbore into the TRV base, and it's a good job I put water proof material down because before I had even got to removing the nut a large amount of air and very black water escaped and the icy cold piece of tubing started to get hot, and I let it carry on leaking into a bowl until the water looked fit to drink

Retightened nut and rad heated up no problem, but I wonder why the air would not escape via the bleed screw which has always had clean water from it, unless the black sludge was the real cause.

Many many thanks for your help

Regards Ravel

 

[JohnD]

black water suggests sediment. Radiator not working might have been because the sediment had settled and clogged it.

You can clean this out using chemicals and a Magnaclean

A sealed system with microbore is not the easiest to clean

A Magnaclean needs a 22mm pipe (not Microbore) on the return to the boiler.

It will be very much easier to clean it out before it blocks again.

Have you got one or more drain valves to empty out the dirty water and loose sediment?

p.s. if instead of " I started to loosen the nut holding the microbore into the TRV base" you had undone the valve from the rad, you could have used the valve to control the flow of water.

 

[Ravel]

black water suggests sediment. Radiator not working might have been because the sediment had settled and clogged it.

You can clean this out using chemicals and a Magnaclean

A sealed system with microbore is not the easiest to clean

A Magnaclean needs a 22mm pipe (not Microbore) on the return to the boiler.

It will be very much easier to clean it out before it blocks again.

Have you got one or more drain valves to empty out the dirty water and loose sediment?

p.s. if instead of " I started to loosen the nut holding the microbore into the TRV base" you had undone the valve from the rad, you could have used the valve to control the flow of water.

Hi JohnD thanks for the info about Magnaclean, and just before this problem occured I had poured 1Litre of Sentinal X400 into the loft header tank and propose to flush it all out after running the system for a couple of weeks, when I will then pour in 1 Litre of X100 inhibitor.

Regarding removing the valve from the rad I would have then had a far less controllable flow from the rad output which would have exceeded the capacity of my capture bowl.

There are unfortuntely no drain valves on my rads, but for the time being the system is fully working, and things can only get better.

Regards Ravel

 

[JohnD]

There are unfortuntely no drain valves on my rads,

available in 10mm and 15mm

Useful on downstairs rads and any that are fed from loops coming down from the ceiling

 

[Ravel]

There are unfortuntely no drain valves on my rads,

available in 10mm and 15mm

Useful on downstairs rads and any that are fed from loops coming down from the ceiling

Thanks for the pic JohnD I'l fit some of those, btw how many do I need with 4 rads upstairs and 3 down, is it just the downstairs with one on each ?

Regards Ravel.

 

[JohnD]

you don't normally need them upstairs, unless you have rads on a loop from the ceiling. the drain will just reduce the water level to the drain, so you will still have to drain the downstairs afterwards.

I fitted one on a bathroom rad so I can drain don to that level only when I want to fit a towel rail, or maybe change a TRV upstairs. Most people would not bother.

Best place is to have them on the downstairs rads nearest to the front and back doors so you can poke a hose out there.

You must however have one on every rad fed from a ceiling loop (usual if you have concrete floors).

 

[Ravel]

Thanks JohnD for your welcomed advice, and I've had a look at a source of drain valves, and they are quite inexpensive so it's one on each of the 3 downstairs rads for me.

Regards Ravel,.

 

[Ravel]

Hi JohnD I have now purchased the valve exactly like your picture but one thing worries me, as my rads are about 20 years old will they have metric thread on the right hand piece of threaded tube in the pic.

I have also thought of not disturbing the existing one in the rad and use the large nut thats on it to connect the new valve, but I'm not sure if that's the same thread also.

I obviously don't want to get everything prepared to fit the valve, and find the threads don't match, the olive on the new valve seems captive so can I use the one on the old threaded tube.

Thanks for any help.

Regards Ravel.