Help with a cold radiator!

30
Posted 30th Nov
Hi everyone,

Just been to my parents house and theyre struggling with a radiator in the main living room. The whole house heating stays on all day but this heater is luke warm at best.

I did a bit of googling and it says to check if its blocked - the inlet pipe is boiling hot but the pipe on the other side of the heater is cold. The whole heater is luke warm - even at the bottom.

We tried draining out some water in case theres a air trapped but no improvement.

Its pretty old - cast iron and thinking it might be better to replace it - its just an unusual size - 1500mm x 750 mm hieght. I guess the hieght might not matter for a replacement?

Any reccomendations for suppliers?
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If bleeding it has not worked,shut it down on both valves then remove it. blast it through with a power washer.|(worth a try).
Before you do that, try turning all the other rads off whilst running the heating only... could just be an air lock which is fairly common.
1850maggie30/11/2019 18:51

If bleeding it has not worked,shut it down on both valves then remove it. …If bleeding it has not worked,shut it down on both valves then remove it. blast it through with a power washer.|(worth a try).


we did that couple of years ago and lots of black sludge came out but its always been worse then the other heaters.



bgdon130/11/2019 18:57

Before you do that, try turning all the other rads off whilst running the …Before you do that, try turning all the other rads off whilst running the heating only... could just be an air lock which is fairly common.


Might try that now, will post back in a hour


**** went to do it and dad just mentioned he tried that this morning
Edited by: "dasachmo" 30th Nov
i found screwfix to be the best for long radiators and this is quite a long one that your parents have. radiator sizes have changed so this is probably comparable but the plumber will need to do a bit of pipe work to fit the new radiator

screwfix.com/p/k…694


i had a similar problem with my living room radiator and thought it was a faulty TRV as they can shut off the flow of hot water in the feed pipe into the radiator if it thinks the room is already at the correct temperature. it turned out to be something else but it could be a fault with the TRV if your radiator has a TRV.
mutley130/11/2019 19:06

i found screwfix to be the best for long radiators and this is quite a …i found screwfix to be the best for long radiators and this is quite a long one that your parents have. radiator sizes have changed so this is probably comparable but the plumber will need to do a bit of pipe work to fit the new radiatorhttps://www.screwfix.com/p/kudox-premium-type-21-double-panel-plus-single-convector-radiator-600-x-1400mm-white/51694i had a similar problem with my living room radiator and thought it was a faulty TRV as they can shut off the flow of hot water in the feed pipe into the radiator if it thinks the room is already at the correct temperature. it turned out to be something else but it could be a fault with the TRV if your radiator has a TRV.



Thanks Mutley - I saw that deal and was hoping screwfix had our size but its so difficult to find a 1500mm one. Was hoping to find the exact size change it myself (even if the radiator is a bit more pricey) rather then buying a cheaper 1400mm one and calling out a plumber - who would probably charge much more

I Checked it now and no TRV unfortunately
If it has a trv fitted, remove the top part of the valve by unscrewing the knurled nut and then try to carefully raise the exposed metal pin with a pair of pliers, it only needs to move a few millimetres. If the radiator then heats up the problem is the trv which you can just replace.
Edited by: "Dyslexic_Dog" 30th Nov
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Try ensuring both valves fully open, see if it heats up. Bleed the radiator.

If that doesn’t work then try changing the valves and giving the radiator a good blast through with water outside.
dasachmo30/11/2019 19:16

Thanks Mutley - I saw that deal and was hoping screwfix had our size but …Thanks Mutley - I saw that deal and was hoping screwfix had our size but its so difficult to find a 1500mm one. Was hoping to find the exact size change it myself (even if the radiator is a bit more pricey) rather then buying a cheaper 1400mm one and calling out a plumber - who would probably charge much moreI Checked it now and no TRV unfortunately


if you google 1500 mm wide radiators there are retailers that do sell them. they are a little more expensive and i don't know about how good the brand is. the screwfix one comes with free TRV at the moment. the kudox premium radiators are very good radiators and they look better than some of the other brands.
dasachmo30/11/2019 19:05

we did that couple of years ago and lots of black sludge came out but its …we did that couple of years ago and lots of black sludge came out but its always been worse then the other heaters. Might try that now, will post back in a hour**** went to do it and dad just mentioned he tried that this morning


Ahh, did he definitely turn every rad fully off with the boiler running on heating only (not hot water aswell if it’s a system one) did the boiler knock off at its temperature? If the rad is heating slowly but the return pipe is cold it will be a blockage or faulty valve.
Best to whip off the radiator, and flush it out manually like 1850maggie said. Attach a hose to one of the pipe valves and open the valve fully, then turn the filling loop on to flush that leg out, and the same the other side. Double check the valves fully open.
Unless your rad is leaking it won’t need replacing. Put some system cleaner in and fit a magnaclean after to help prevent it happening again!
Edited by: "bgdon1" 30th Nov
bgdon130/11/2019 20:23

Ahh, did he definitely turn every rad fully off with the boiler running on …Ahh, did he definitely turn every rad fully off with the boiler running on heating only (not hot water aswell if it’s a system one) did the boiler knock off at its temperature? If the rad is heating slowly but the return pipe is cold it will be a blockage or faulty valve. Best to whip off the radiator, and flush it out manually like 1850maggie said. Attach a hose to one of the pipe valves and open the valve fully, then turn the filling loop on to flush that leg out, and the same the other side. Double check the valves fully open. Unless your rad is leaking it won’t need replacing. Put some system cleaner in and fit a magnaclean after to help prevent it happening again!


Okay so it heats a bit but stays luke warm. (barely noticeable). I have a feeling it's completely blocked inside as it's always been cold... Worth buying a new one?

I've seen
plumbingworld.co.uk/kar…tor

Which is a but shorter but not sure of the company and £25 for delivery.
dasachmo30/11/2019 21:10

Okay so it heats a bit but stays luke warm. (barely noticeable). I have a …Okay so it heats a bit but stays luke warm. (barely noticeable). I have a feeling it's completely blocked inside as it's always been cold... Worth buying a new one? I've seen https://www.plumbingworld.co.uk/kartell-kompact-600mm-high-x-1500mm-wide-double-panel-radiatorWhich is a but shorter but not sure of the company and £25 for delivery.


Always been cold since installing the rad or was it there and not working when the house was bought?
I’d still flush out the pipe work to the rad and check the valves are fully opening up as a minimum before buying a new one, and try flush the rad out yourself first, even rads the same size may need the pipe work altering if it’s a different manufacturer and you have no play in the pipe work, plus you will have to fit new brackets etc.
Check that trv is working properly first, if ok,
follow this video to remove the rad

Worth then opening the remaining pipes a little bit to see if the water is flowing
Ok so we know you’ve tried turning off all order rads, have no TRV and it’s been pressure cleaned previously.
Can you remove the radiator and bridge the 2 valves with a length of pipe? If hot water flows through the bridge, then it’s the radiator. If not it’s the exit valve.
Oneday7701/12/2019 00:26

Ok so we know you’ve tried turning off all order rads, have no TRV and i …Ok so we know you’ve tried turning off all order rads, have no TRV and it’s been pressure cleaned previously. Can you remove the radiator and bridge the 2 valves with a length of pipe? If hot water flows through the bridge, then it’s the radiator. If not it’s the exit valve.



Thanks for your advice and reading the thread too. No trv but I'll try this again tomorrow.
The heating was working but I remember them saying the living room is always colder then the rest. It's weird because some heaters get a lot hotter then others.
I'll try the valve tomorrow but bear In mind the heaters are at least 20 years old if not more.

Ill try to bridge it and play with the exit valve.
Do you have a hot water cylinder? The fed valve on mine needs to be restricted slightly, or otherwise most of the hot water circulates through the heating coil limiting the flow to some of the radiators. If you do and there's also a three port valve, feel the pipes to check the flow to the hot water cylinder is actually cut off when you've selected central heating only, as some are known for the return spring breaking off (EDIT: thinking about it, you would have noticed you hot water getting too hot if you had a faulty motorised valve), and also check the bypass valve is set right.

We have a couple of radiators in our extension where the feed pipes loop into the loft, although there's manual vent valves on the raised pipes there to release the trapped air, we still usually get an airlock when we drain our system. Turning the pump to max speed, setting the programmer to heating only and closing all but the cold rads and opening their lockshield valves fully usually sorts it out.


If you remove the radiator and flush it out with a hose/jetwasher, while flushing it give it a bit of a bang with a rubber mallet to loosen up the debris, or with something else that won't harm the paintwork.
Edited by: "melted" 1st Dec
39213650-j6veq.jpgThat's the cold outlet valve. It's opened fully and pipe is cold.

The heaters luke warm at the hot intake side and gradually colder / stone cold at the outlet.

When I opened and closed it water trickled out from the pin.
Going to flush it today. Fingers crossed.


Dad's set on getting a magna clean instead but telling him to try this first.
Edited by: "dasachmo" 1st Dec
Will keep you updated but this is what's coming out. 39215925-g3Nwo.jpg
Inhibitor and a magnaclean will go a long way after flushing the whole system.
And a trv while your there.
It could well be too hot in the room if you get it working!
39217961-Mhot1.jpghahah , fingers crossed, just reattached it, out of interest - magnaclean or fernox tf1?

We have a spare radiator gap , can we stick it here?
Edited by: "dasachmo" 1st Dec
dasachmo01/12/2019 15:31

[Image] hahah , fingers crossed, just reattached it, out of interest - …[Image] hahah , fingers crossed, just reattached it, out of interest - magnaclean or fernox tf1?We have a spare radiator gap , can we stick it here?


What heats that area now?
Can't see why not, just looks an odd place to put one (and the fittings on those cleaners are designed to fit on a cut pipe)
We've got another heater in the kitchen so it's strange they put another


Really annoyed though... Put the radiator back on and no improvement.
dasachmo01/12/2019 16:00

We've got another heater in the kitchen so it's strange they put …We've got another heater in the kitchen so it's strange they put anotherReally annoyed though... Put the radiator back on and no improvement.


Did you check there was a bit of flow from both sides without the rad?
Yup. There was water from both sides. The outflow side was dripping too but think the valve is just a bit loose so didn't tighten all the way.
dasachmo01/12/2019 16:27

Yup. There was water from both sides. The outflow side was dripping too …Yup. There was water from both sides. The outflow side was dripping too but think the valve is just a bit loose so didn't tighten all the way.


Hmmmmm.....and you say the pipe leading to the rad feels hot and progressively colder the nearer it gets?
Did the rad fill up quickly with lots of noise from the water flowing into it, and lots of air from the open bleed valve?
Yup. So the inflow pipe is hot right up until I meets the radiator. Goes into the radiator which is luke warm. Outflow pipe cold.

Put the radiator back on and could hear it fill up/trickling inside. Used the bleed valve until no more air coming out.

Updated ---
I just went and bled the radiator for about 10 mins,
hot water came out and the radiators heated up but im not sure if thats just because i bled it or if waters actually circulating around. Possibly could have a air block / lock (excuse the lack of terminology ) on the outflow pipe?
Edited by: "dasachmo" 1st Dec
Sounds like the hot water is feeding into the rad but not flowing through. Sounds like either a faulty lockshield ( Outflow ) or the pipework from the lockshield is blocked, not allowing the system to flow correctly.
Edited by: "ajm007" 1st Dec
Where does the outflow go, does it go past a rad that heats up?
im not sure, it just goes straight into the floorboards and i dont think dad knows which radiator the pipe goes to next

I could try replacing the valve on outflow?
dasachmo01/12/2019 21:05

im not sure, it just goes straight into the floorboards and i dont think …im not sure, it just goes straight into the floorboards and i dont think dad knows which radiator the pipe goes to nextI could try replacing the valve on outflow?


Worth s shot, and you can then see what's blocked or rather, as you'll need to drain the system to do that, taking off the old one should reveal if the valve or the pipe is the problem.
You could find a large build up of sludge in the pipe, and only a proper power flush will sort out.
dasachmo01/12/2019 17:03

Yup. So the inflow pipe is hot right up until I meets the radiator. Goes …Yup. So the inflow pipe is hot right up until I meets the radiator. Goes into the radiator which is luke warm. Outflow pipe cold. Put the radiator back on and could hear it fill up/trickling inside. Used the bleed valve until no more air coming out.Updated --- I just went and bled the radiator for about 10 mins, hot water came out and the radiators heated up but im not sure if thats just because i bled it or if waters actually circulating around. Possibly could have a air block / lock (excuse the lack of terminology ) on the outflow pipe?


Shouldn't take 10 minutes to bleed a rad.

Could try attaching a hosepipe to the valve on the outflow if you can find a suitable fitting (a tap connector fits mine) so you can run some water out and hopefully clear any sludge or airlock in the pipe (obviously turn the boiler/pump off first). Also try hooking the other end of the hose to the garden tap and another hose to either your drain point or the other tap for the same radiator, so that you can flush the pipework out.
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