Radiators Not Working After New Valves Fitted

MiniAmethyst

Hello – I’m a long time reader, first time poster, and I’d be very grateful if anyone could shed some light on what’s going on with my radiators!

This is a little convoluted, so I’ll try to keep it as succinct as possible…

My family recently moved into a new (rented) house. Every radiator valve was leaking, which meant the boiler would run out of pressure literally every hour, and so had to be frequently topped up. BUT when the boiler was topped up, every radiator was boiling hot and worked perfectly.

Two days ago, the landlord’s plumber came and fitted new thermostatic valves to every radiator (before this, every radiator just had those old-fashioned caps, so they were either on or off – you couldn’t control the temperature).
Since the new ones were fitted, only three of the radiators in the house get properly hot. All the others are just lukewarm (with some being actually cold most of the time), even when the thermostatic valves are turned up to full.

Also, if you set the digital thermostat to, say, 24 degrees, the house can never get higher than about 21 degrees. It gets to about 21 degrees and then all the radiators start cooling down, even the ones that work properly. This never happened before the new valves were fitted – if you set the thermostat to 24, the house got up to 24, and then the radiators started cooling down.

My Mum noticed that the actual pipes leading from the floor to the radiators are absolutely boiling, even to the radiators that are lukewarm. She also noticed that the new thermostatic valves were about 0.5cm narrower than the original valves. A boiler engineer who came out a few weeks ago said that the whole system probably needed flushing out because the water in the boiler was dirty. Could it be that there’s sludge in the system, and the water is having trouble getting through the new narrower valves?

We spoke to the landlord about all of this, and the landlord’s plumber came round again today, touched the one radiator downstairs that works and said it felt hot enough to him, and then simply ignored the colder radiators even when they were pointed out to him. Then he left.

He did say, however, that the thermostatic valves were specially made to stop the radiators from “getting too hot” to save on gas. I would really love to know what this means in practical terms. Is this why the radiators don’t work properly? Why would anyone fit such valves, especially as we pay the gas bill, not the landlord? Are all thermostatic valves made this way?

If anyone can shed any light on what’s going on, I would be so grateful. I just can’t see why the radiators worked fine before the valves were fitted. Thank you so much for taking the time to read this and I’m sorry it’s so long! Thanks again.

Streaky_Bacon

If the valves have been fitted properly and are opened up to full then the radiator should pretty much get as the pipe feeding them.

The most likely problem and one of the first things to check is whether the radiators need to have air bled from them. If you haven't done it before, it's very straightforward

Another simple thing to check is whether the lockshield valve (the valve at the other end of the radiator) is open.

This guy does excellent plumbing videos, and here is one on fixing cold radiators that covers bleeding and the lockshield valve amongst other things.

https://www.youtube.com/watch?v=wqku_Rc_YuI

All of the above should have been checked by the plumber, but it sounds like he is not a lot of help.

MiniAmethyst

Thank you SO much for that link!! The plumber said he bled all the radiators, but I had a chance to watch him do two of them, and he only had the key in for a second, and I'm sure he took it out before any water came out. It might be that I mis-saw, but I was watching really closely, and I'm sure no water came out. I ordered a key from Amazon yesterday which should arrive tomorrow, so that's definitely something I'll try as soon as it comes.

In the meantime, I've just tried opening the lockshield valves on the ones that aren't working, so I'll see how that goes! That was a fantastic tutorial, especially as it mentioned at the end that they had another video on the same channel about balancing the heating system, which I'm going to try tomorrow if opening the lockshield valves isn't enough. Definitely subscribing!!

Thank you so, so, so much -- it will be SO amazing if this works!

Cardew

The balancing will probably be the cure to the problem. Just adjust the lockshields a little bit at a time and wait a couple of minutes.

matelodave

Thermostatic rad valve will reduce the radiator temperature so they may only get lukewarm but you can check if the rad is working properly by removing the thermostatic element (they are usually only screwed on). Get hold of the installation instructions (download one if necessary) to see how they are fitted and how to reset the maximum temperatures.

We had some that had adjustable stops which could limit the temperatures that could be set. TBH I'd check those first before faffing around with the lockshield valves.

To do it properly you really need to check the temperature drop across each radiator to balance the system otherwise some could effectively short circuit the heating system and starve other rads from hot water.

[Deleted User]

Streaky_Bacon wrote: »

If the valves have been fitted properly and are opened up to full then the radiator should pretty much get as the pipe feeding them.

The most likely problem and one of the first things to check is whether the radiators need to have air bled from them. If you haven't done it before, it's very straightforward

Another simple thing to check is whether the lockshield valve (the valve at the other end of the radiator) is open.

This guy does excellent plumbing videos, and here is one on fixing cold radiators that covers bleeding and the lockshield valve amongst other things.

https://www.youtube.com/watch?v=wqku_Rc_YuI

All of the above should have been checked by the plumber, but it sounds like he is not a lot of help.

I used this guy s youtube to find out why two of my rads were cold even though pipes were hot..Was sticking pins on the lockshield valves. A gentle push down on them released them and they ve both worked fine now for two years.. They must fur up a bit sometimes with the calcium deposits

Talldave

matelodave wrote: »

Thermostatic rad valve will reduce the radiator temperature so they may only get lukewarm but you can check if the rad is working properly by removing the thermostatic element (they are usually only screwed on). Get hold of the installation instructions (download one if necessary) to see how they are fitted and how to reset the maximum temperatures.......

Thermostatic valves do not reduce the radiator temperature - the water in the system is all the same temperature (set at the boiler) - they simply shut off the radiator when the preset temperature is reached. Of course that means that the radiator spends more time cooling down and heating up - but it still runs at the system temperature when it's on.

As suggested above the OP's problem is most likely the lockshield valve (if the whole radiator is cold) or air needing bleeding (if the radiator is hot at the bottom and cooler at the top). If the installation had been done properly, neither problem would exist. Although a re-bleed after a few days is probably a good idea.

matelodave

Talldave wrote: »

Thermostatic valves do not reduce the radiator temperature - the water in the system is all the same temperature (set at the boiler) - they simply shut off the radiator when the preset temperature is reached. Of course that means that the radiator spends more time cooling down and heating up - but it still runs at the system temperature when it's on.

As suggested above the OP's problem is most likely the lockshield valve (if the whole radiator is cold) or air needing bleeding (if the radiator is hot at the bottom and cooler at the top). If the installation had been done properly, neither problem would exist. Although a re-bleed after a few days is probably a good idea.

The radiator will only get up to full temp if the room temperature allows the thermostatic valve to fully open which is when the room is cold. They dont work like an on/off switch, they slowly close and open depending on the room temperature so there are situations (in fact most of the time) when they are only partially open

As they effectively modulate the water flow through the rad they actually do reduce the radiator surface temperature. As the flow reduces then the amount of hot water in the radiator will decrease, thus it will feel cooler. If they are working correctly then the rad will stay at a lukewarm temperature unless the room temp drops well below the set temperature

Talldave

matelodave wrote: »

The radiator will only get up to full temp if the room temperature allows the thermostatic valve to fully open which is when the room is cold. They dont work like an on/off switch, they slowly close and open depending on the room temperature so there are situations (in fact most of the time) when they are only partially open

As they effectively modulate the water flow through the rad they actually do reduce the radiator surface temperature. As the flow reduces then the amount of hot water in the radiator will decrease, thus it will feel cooler. If they are working correctly then the rad will stay at a lukewarm temperature unless the room temp drops well below the set temperature

Ok but there seems to be a misconception about thermostats that they in some way affect the speed of heating (e.g. people who think cranking the room stat to 30 makes the house wsrm up faster).

In a cold house with TRVs set to different settings all the radiators will initially run at the system temperature. I just felt the earlier post would give people the wrong idea that some radiators magically get fed with cooler water. (Let's ignore the flow/return differential!).