Advice on Cold and Warm radiators on second floor

[Milleniumaire]

Hi, with the weather now getting cooler, I've been checking the radiators around the house and have noticed a couple of issues on the 2nd floor. This is a loft conversion done many years ago and it consists of a large room with two medium sized radiators and an en-suite bathroom with a medium sized towel rail. The radiators are both fitted with Westherm Four TRV's, however one of them isn't working. The other radiator is working but isn't getting hot, only warm and the tower rail also isn't working in that it never gets warm.

To troubleshoot, I've turned up the thermostat in the hallway to force the heating on. Checking the radiators on the ground floor and 1st floor, they are all very hot.

Tried bleeding both radiators and the towel rail in the loft and water came out as soon as I opened up the bleed valves.

For the radiator that isn't working, I've removed the top of the TRV and the pin was down. Pulled it up with some plyers, then pushed it down again and it didn't pop up. Used WD40 on it and manipulated it with a pair of plyers, but no joy. Tapped the valve while it was pulled up as I assumed the pin wasn't connected to the washer in the valve, but unable to release it, assuming the valve is stuck closed. The other possibililty is the lack of water pressure given that the other working radiator is only warm, not hot!

The partly working radiator has a working TRV, the pin pops up and I can push it down easily. The supply pipe to the TRV is hot, but the radiator itself is only warm and even after removing the TRV head, with the pin up, the radiator doesn't get hot and stays warm. I've ensured the lockshield valve is open.

The towel rail doesn't have a TRV, just two valves, one which can be turned, but doesn't seem to turn very far; about 3 turns. The other valve (the lockshield?) requires a screwdriver in the end and I've fully opened it. Regardless of what position either valve is in, I can't get any heat into the towel rail.

The flow and return pipes to both the towel rail and the radiator with the failed TRV are cold.

It looks like I'll have to change the failed valve, but I'm not sure why one of the radiators is only getting warm and why the towel rail, or its piping isn't getting warm. Does this suggest an air lock/blockage preventing hot water getting to the radiators and the towel rail?

Any suggestions would be welcome.

 

[terryplumb]

have the rads in loft ever worked properly ??? try closing trv 's on all ground and first floor rads to off , and report back results.

 

[Milleniumaire]

Yes, the loft rads have worked fine until now. I will trying increasing the water pressure by turning off all other rads in the house.

 

[Milleniumaire]

So, I turned all the radiators off after making a note of the lockshield positions and left on only the 2 loft radiators and the loft towel rail. Turned up the heating thermostat and the heating temperature at the boiler and ensured the boiler started up.

Eventually the working radiator and the towel rail in the loft warmed up. The loft radiator with the broken TRV stayed cold as did the pipes supplying it.

Left it like this for about an hour, but they never got too hot to touch. Turned all other radiators back on and kept the heating up high for a couple of hours. All radiators in the house were too hot to touch except those in the loft which appeared to have got cooler and were now only luke warm.

At least there's now some heat in the towel rail, but I'm not sure why the loft radiators aren't getting as hot as the rest of the house.

Maybe I'll replace the broken TRV and possibly even the other TRV in the loft as they were fitted at a similar time (as part of a loft conversion about 15 years ago). I have been thinking of draining the system as part of adding some new inhibitor, so might use this as an opportunity to do that, then attempt to re-balance the radiators in the hope that this makes a difference.

 

[terryplumb]

when turning off all other rads ,you should have used the trv's ( as advised in my post ) and not touched the lockshields as they are used to balance the rads. so you have a trv that doesn't work and needs replacing ,and it appears that your system is not balanced .however ,you stated earlier that the loft rads did work fine at some point ,is it possible that the lockshields have been tampered with on some rads since the system worked fine ?by the way what size is the pipework to loft rads and other floors rads ?

 

[JohnD]

is there a hot-water cylinder?

did it get surprisingly hot when you turned off all the hot radiators?

 

[Milleniumaire]

what size is the pipework to loft rads and other floors rads ?

The pipework from the boiler is 22mm. The exposed pipework to the rads on the ground and 1st floor is 15mm. As the loft extension was done after the house was built, I believe only 15mm piping feeds the loft. Not sure exactly where they connected upto the existing piping on the 1st floor.

is there a hot-water cylinder?

did it get surprisingly hot when you turned off all the hot radiators?

Yes, we have an unvented hot water cylinder next to the boiler (in the garage). I didn't notice the hot water getting hotter.

Over the last year a couple of motorised valves have been replaced requiring the system to be drained down, so I guess the lockshield valves could have been adjusted then, but not sure why they would have been.

I will investigate balancing the radiators and see if that makes any difference.

I'm looking to replace the two loft TRV's. I would like to choose a type where the "pin" is connected to the washer. Does anyone know of a particular make where this is the case. I have a mix of TRV's throughout the house, some use a screw nut to attach the head, but most require an alan key, which isn't as convenient. Any recommendations for good TRV's that use screw nuts to attach the head?

 

[JohnD]

if you turn off all but two rads; and those two don't get very hot, then either there is a severe obstacle to circulation, or the heat is going somewhere else. Faulty radiator valves in the loft would count as an obstruction.

We'll say the heat isn't going to other radiators, because you'd have noticed. It might be going to the cylinder, so set HW to "off" and feel its pipes. It might also be going round a bypass, which with luck will be close to the boiler and not hidden under a floor. If it is, you'll find the Return pipe on the boiler is just as hot as the Flow, even if your bad radiators aren't.

If the boiler isn't sending heat anywhere, then you'll notice it stops firing and uses hardly any gas.

It's just about possible that the loft rads are on a one-pipe system, either accidentally or by design, but even then, they should heat up eventually.

 

[Milleniumaire]

Looking at replacement TRV's it would appear the Drayton TRV4 or the Honewell Valencia VT200 get good reviews. They are described as having "Integrated radiator balancing insert". What does this mean?

As I plan to replace both TRV's in the loft I've been looking at the separate wireless thermostats that drive the TRV's i.e. control both TRV's from one thermostat. This is probably overkill, but interested to know what your thoughts are on these wireless TRV's. I confess I'm not a fan of anything that requires a battery!

 

[Milleniumaire]

Another question

While looking at TRV's it seems the Drayton TRV4 is cheaper to purchase if bought as a set; TRV and lockshield valve, so I was think I would probably drain the system and remove the radiators to flush them through outside, then I may as well replace the lockshield valve as well as the TRV valve.

However, on checking the existing lockshield valves of the two loft radiators, they are unlike any in the rest of the house. The connection to the radiator is via a large nut, rather than the usual smaller 15mm compression fitting. Here's what it looks like:



The TRV valve looks like this, which is pretty standard:



Is the strange lockshield connection to the radiator specific to this type of radiator i.e. only a specific type of lockshield can be used? This has put me off changing the lockshield valve as I think the replacement would take up much more space and so the piping wouldn't be wide enough, plus the radiator connections look different due to that large nut.

 

[Chunky Chicken]

Sounds like a tired pump to me.

 

[Milleniumaire]

It's been a while, but I finally found time to replace the TRV's of the two radiators in the loft with a couple of Drayton TRV4's. Was planning to completely drain the system and fill up with fresh, clean water and some new inhibitor but had a problem with one of the bedroom radiators as I was unable to open the bleed valve. I ended up half draining and just changing the TRV's. The job went well (no leaks ), however I still have EXACTLY the same issue; only one of the loft radiators get's hot! At least I've now ruled out a faulty TRV as the cause of the other radiator not working. As the loft radiators were installed after the house was built I'm now wondering exactly how they have been connected upto the existing heating system, such that only one of the three appears to work!

What to do next?

 

[dilalio]

Can’t be arsed to read all the above.
Is your CH gravity fed?
If so, seal it up and change the pump.

 

[terryplumb]

So one rad doesn't heat up and nor does the towel rad in en suite ? You told us in earlier posts that these problem rads are in a loft conversion ,that was done many years ago ,and these rads all worked fine until recently . so the plumbing layout / installation to them isn't really an issue. I suspect the system is not balanced . is your central heating water a sealed system ( pressurised ,and with a pressure gauge). You need to sort out the rad with the faulty air bleed valve ,and ensure that all air is removed from the system. Once that's done , turn off all trv 's except one of the loft rads that won't heat. Run boiler to temp only on central heating mode ( not domestic hot water ) and see if that rad gets to full temp. If it does open the trv on the second loft rad ,see if both are then getting up to temp. If so open towel rad valve and see if that gets to temp. If all these problematic rads are then working fine ,with all others off on ground and first floors , try opening all other trvs. Report back on results

 

[Milleniumaire]

Hi Terry, yes you've got it right. Regarding the plumbing layout, I agree, but I was so surprised that fitting a new TRV didn't resolve the issue with the 2nd rad as I'm 90% sure the old TRV was stuck down as the pin wouldn't move on it's own, even after trying to free it up with pliers and WD40. It has made me wonder if the lockshield valve on the other side of the radiator may be an issue, but I suspect not as that is normally open all the time. Even the pipes feeding this radiator never get even slightly warm. Same with the towel rail. In terms of physical positioning, the radiator that is working is in the middle of the house, with the towel rail and other none-working radiator at each end of the house. I'm not exactly sure where the pipes that run from the 1st floor to the loft are located, but assuming they run to the middle, working radiator first, turning both valves off on this radiator doesn't cause either the other radiator or the towel rail to heat up. which I would have expected to happen as they aren't that far apart!

The system is a sealed, pressurised system. I thought the bedroom radiator with the faulty bleed valve would be a problem to heat up due to trapped air, however, it is red hot all the way to the top so looks like there isn't any air trapped in it, which means I don't need to rush to fix it immediately, but will be looking for a replacement over the next couple of weeks.

I will try what you suggest one evening this week and let you know how it goes.

Thanks.