New radiator staying cool at the bottom

[dougie212]

I've just fitted a new radiator with Drayton TRV and lockshield. I understand that the valves are bi flow and so for ease of access the TRV is on the right of the radiator. The radiator is heating up but is staying cool at the bottom and I have lifted the floorboard at the trv end and that is also cool too. I have isolated that radiator and it does eventually warm through but doesn't heat up as normal, the bottom and right hand corner almost just conducts the heat rather than gets hot if that's makes sense. I've tested the pin in the trv and it will push down a little and springs back up. I was going to try and put some central heating cleaner through and see if that helped, and either move the sludge or release a possible airlock but I'm a bit baffled. Would the easiest thing be to take the rad off and make sure the trv is opening? My boiler is a combi boiler, and prior to the new rad and new valves going on the old smaller radiator heated up fine. All other radiators heat up lovely, I just have a feeling nothing is passing out of the trv side of my new radiator.I'm stumped... thanks in advance.

 

[PlumbBobBob]

is it a bi-directional trv? can you see any arrows on it at all? do you know the model number of it?

 

[Frog67]

Sounds like an airlock,just double check both rad valves are open, check system pressure at boiler,if ok you could turn off the other rads and see if that cures it

 

[Dotty]

Sounds like an airlock,just double check both rad valves are open, check system pressure at boiler,if ok you could turn off the other rads and see if that cures it

So how do you come to that conclusion?

 

[Frog67]

So how do you come to that conclusion?

Err... rad not getting hot, all others seem ok, bi-directional TRV, luke warm pipes to valves.
I thought it was always best to try the easiest things first.
I could be wrong though

 

[Dotty]

Err... rad not getting hot, all others seem ok, bi-directional TRV, luke warm pipes to valves.
I thought it was always best to try the easiest things first.
I could be wrong though

You see the bit where it says cold at the bottom. ....

How long did you say you were out of the game?

I'm not having a dig mate, I'm honestly using this as a gentle reminder that it's important to read the whole question before committing an answer. Learning to learn again is probably the hardest part of the ACS. Especially for us older boys.....

 

[Dotty]

Actually. ..... now I've had a think on it. .......

Carry on Froggy old son. I've not had a lot of sleep this last month. I'm finding just lately it's wood and trees.......

 

[Frog67]

Fair point, but he is asking should the easiest thing to do would be to take the Rad off?
My opinion would be to close the other Rads down to see if that sorts it before doing anything more drastic.
Makes sense to me

 

[Dotty]

Fair point, but he is asking should the easiest thing to do would be to take the Rad off?
My opinion would be to close the other Rads down to see if that sorts it before doing anything more drastic.
Makes sense to me

Always worth a punt.

 

[Frog67]

Yep

 

[Billy Bob Bob]

Actually. ..... now I've had a think on it. .......

Carry on Froggy old son. I've not had a lot of sleep this last month. I'm finding just lately it's wood and trees.......

I Was just about to say WTF is he on about ,froggys right could be a airlock,was waiting for you to have a think on that one LOL

 

[Dotty]

I Was just about to say WTF is he on about ,froggys right could be a airlock,was waiting for you to have a think on that one LOL

Hehehe you know me minds been elsewhere this month. ....

 

[drip-dry]

Oh...how boootifullll...a bonding moment........:bow::bow::25:

 

[drip-dry]

As for air lock..yeh..right..... Think flow rate and reasons for maybe...

 

[JCplumb]

I have isolated that radiator and it does eventually warm through but doesn't heat up as normal.

Can't be sure but I think this bit means the OP has closed all other rads and this one still performs badly.
At this point I think the easiest option is to take the rad off. The OP fitted the rad himself so shouldn't be too technically difficult for him.
Boiler off, plenty of towels down, close both valves(using the decorators cap on the TRV), crack the nuts and drain just that rad. Take it off and in turn - open the valves into buckets. A half inch flexi tap connector will screw onto the open end of the valve for better control as long as it's not a union type.
An airlock will be obvious, there will be spluttering, run it off until the spluttering stops.
A blockage because of sludge will mean that the valve may just trickle. In the past I have had someone top the boiler up to 2 bar or so and that got the blockage out, it can come out like a cork in a bottle though so be ready.
Get the pressure back to 1bar(or whatever your manual tells you) before you turn the boiler back on.

 

[Best]

Could be anything causing slow flow through rad, - a dot of system dirt in the new TRV would easily block the tiny hole in the valve.
One of the new valves could be faulty, although rare.

 

[joni os]

Towel on floor, close both valves, then remove air vent bleed screw. Open one valve at a time. On pressurised system, water will exit rad as a jet stream and can be caught in bucket.
This will confirm both valves function correctly. Will also clear air locks in system and stands good chance of forcing through any sludge causing reduced flow through valve.
If necessary top up pressure, because when pressure drops to zero a vacuum is created and water will stop flowing from rad. Opening, closing and reopening valve and gentle tapping is often sufficient to promote flow.

 

[dougie212]

Thank you for your resposnses everyone. Joni Os, if I take the bleed screw all the way out will I not create a problem with a seal when I come to put it back in?? Or should it be ok? I was half tempted to undo at least the trv side valve and see if I could get something to pass through it. I suppose being my first experience of a trv I don't trust it really.

 

[joni os]

Your bleed screw is normally a small threaded piece of brass ending in a pointed cone internally and the square head externally. Removing and replacing should not cause problems. The greatest danger, because of its small size, is dropping it through a gap in the flooring.

 

[dougie212]

I think I have solved the problem, I drained the system, shut off all the radiators apart from the dodgy one, and with a hose attached to the drain valve and leaving it open turned the water on, let it flow through. A huge splutter of air came out and a load of black muck.. result!! now having an issue getting the boiler to ignite after refilling but thats in a new thread if you wouldn't mind having a read and seeing if you can help.. Thanks!!