cold rad

[PaulRB]

Thing is, I've shut off all the other rads and I've shut off just the towel rad and it still hasn't helped.
The new rad is a direct replacement for the old one.
I know from talking to people that this is a very common problem. A rad stops working for no apparent reason, usually when you switch on the heating for the first tine after summer.
Thanks

 

[Phil]

Can't really suggest anything that hasn't already been said other than fitting auto air vent is a bad idea. Yes if it is air it will work but when you move house it will be still there under the floor unseen and may cause a plumber agro!

Like the diy'er who tiled his bathroom floor over his c/h pump and a year later it needed replacing.

Nothing worse than working on a system thats been 'messed with'.

Get those carpets up Paul!

 

[fuzzy]

have you drawn the water through each pipe yet?

 

[PaulRB]

Sorry, haven't had time yet. Still gotta work!
I hope to have a go on Thursday.
Realise I don't need to put a draincock on the flow pipe, I'll just turn off the valve at the rad. That way I know when I drain some water from the return pipe it must be replaced with water from the return pipe, and hopefully will flush out any air in the pipe.
I'll let you know how I get on.
Thanks

 

[fuzzy]

some drain off valve combinations require the return valve to be open, it may be difficult for you to ensure flow from the flow pipe if this were to be the case

 

[PaulRB]

Ok, but I plan to shut off the flow valve while I drain water from the system.
With that valve closed I know the water coming out must be from the return pipe ( can't come from the rad because there will be nothing to take its place ).
I hope that will force any air out of the return pipe ahead of the water.
If it works I will then re-open the flow valve knowing there must be no air in the pipes.
Then I'll see if the circulation returns to the rad.
I'm really hoping that, when I open the draincock, I will hear spluttering and know air is coming out!!
If I can clear all air out of these 2 pipes there should be no reason for the water not to circulate.
If it still doesn't work at least I know it can't be an air lock.
Gonna try this tomorrow.
Thanks again.

 

[fuzzy]

Ok, but I plan to shut off the flow valve while I drain water from the system.
With that valve closed I know the water coming out must be from the return pipe ( can't come from the rad because there will be nothing to take its place ).
I hope that will force any air out of the return pipe ahead of the water.
If it works I will then re-open the flow valve knowing there must be no air in the pipes.
Then I'll see if the circulation returns to the rad.
I'm really hoping that, when I open the draincock, I will hear spluttering and know air is coming out!!
If I can clear all air out of these 2 pipes there should be no reason for the water not to circulate.
If it still doesn't work at least I know it can't be an air lock.
Gonna try this tomorrow.
Thanks again.

mmmm, id be more confident if you did the same with the flow, your only pulling water from return, you really should do the same with the flow to ensure 100% you have no air

 

[PaulRB]

Yeah, I will.
Thanks

 

[fuzzy]

let us know how it goes

remember you must do the same with both pipes to ensure there is no air in them. doing it with one valeve closed only ensure that pipe has not air in it

if you only do it with the return as you suggest it only ensure the air is out of that one, doesnt prove anything with the flow

after tyhis it may not be air but at least you can eliminate it once and for all

 

[PaulRB]

Ok Guys, ( especially Fuzzy ), this is what I've done today, Saturday.
Tied up the ball-cock in the expansion tank so it doesn't fill with new untreated water.
Turned off both valves on problem rad. So any water I drain must come from return(-) pipe and not from rad or flow(+) pipe.
Opened draincock and drew off 1/2 bucket of water. Plenty of spluttering and flow stopped for 1/4 to 1/2 a second before continuing, so obviously a lot of air in return(-) pipe.Took bucket up into attic and refilled expansion tank.( level had not dropped below outlet pipe so no air being drawn into system )
Repeated process and this time water flowed as normal.( refilled expansion tank )
Opened both rad valves and drew off another 1/2 bucket in case there was air in the flow (+) pipe but water flowed nicely. ( refilled expansion tank )
Went round and turned off all other rads and put heating on.
5 mins later we had hot water coming thru pipes and rad got very hot. Turned all other rads back on and ran system for 1 hour. Everything ok.
However, I've had the rad working before so I won't know if this has solved the problem yet. I've turned the heating off and I'm gonna let it cool right down for 24 hours and then fire it up again.
Fingers crossed!!
At least I know there was air in the pipework, now I have to wait and see whether air is getting into the system, which is a different problem. I hope the air was trapped in the pipe when I refilled after replacing the pump and, now I've purged the system, it works as normal.
I'll let you know tomorrow.
Thanks guys.

 

[fuzzy]

fingers crossed, keep us posted

 

[Halesowen1]

Balance the system.

 

[PaulRB]

Ok.
So far so good.
Put the heating on this pm and hot water came thru straight away.
Still not 100% sure the problems solved. It'll take a few days of working before I can relax and put it out of my mind.
I still have to balance the system
Meanwhile I will keep you all posted as the week goes on.
If air isn't getting into the system I should be alright.
I know a lot of people have this problem and are following the thread so I think I should point out some of the main points because different systems and installations would require different solutions.
However, with all the help on hand here, I'm sure most problems can be solved.
I have a gravity fed, 2 pipe system with an expansion tank in the attic.
There is a cylinder in the airing cupboard together with a 3-port valve and pump.
The boiler is in the garage.
Downstairs our floors are concrete so all the downstairs rads are fed from above in a "loop" system.
All downstairs rads have draincocks on their pipework so that when you drain the system, you have to go round each rad and drain them individually if you want to completely drain the system.
I understand that the "loop" system is susceptible to air locks when filling up the system and that appears to be whats happened to me.
I've been lucky because I have draincocks on every rad but other people may not so the things I've tried may not work for everyone.
However, the amount of help and support provided by the guys on this forum should enable everybody to solve their problem.
I thank you all for taking the time and trouble to help out and sticking with it when nothing seemed to be working.
My wife thanks you all too!!!
Hopefully I will report that all is working fine in a weeks time.
Cheers

 

[PlumbBobBob]

fingers crossed all goes well

 

[PaulRB]

I'm crossing everything mate!!!