Radiator just won't get hot

IvyFlood

Hi

I have a large radiator in my hallway that just doesn't get hot. This one alone with a vertical one in the kitchen, and one in the sunroom - all near each other and I think are all on the same connection and all never really get hot. 

Tried bleeding, also looked at the pin - all fine. I have also tried balancing the system. I turned off all the upstairs and other rads bar these three and they did get hot! But then as I gradually turned up the other rads, the boiler lost pressure! Not sure if this is normal? I topped it back up but when I've continued to have the heating on these three rads are worse than ever! I'm not so bothered about the other two but the one in the hallway would make such a difference if it got hot and I just feel depressed about paying for heating and not getting the full benefit. It did actually used to get really hot and the heat would hit you as you came down the stairs.

The boiler, radiators and downstairs pipework was all replaced in 2020/21 but I feel its worked since then.

Does anyone know what the problem could be? I do have someone booked to come and investigate but just wondering in the meantime. 

WIAWSNB

IvyFlood said:

Hi
I have a large radiator in my hallway that just doesn't get hot. This one alone with a vertical one in the kitchen, and one in the sunroom - all near each other and I think are all on the same connection and all never really get hot. 
Tried bleeding, also looked at the pin - all fine. I have also tried balancing the system. I turned off all the upstairs and other rads bar these three and they did get hot! But then as I gradually turned up the other rads, the boiler lost pressure! Not sure if this is normal? I topped it back up but when I've continued to have the heating on these three rads are worse than ever! I'm not so bothered about the other two but the one in the hallway would make such a difference if it got hot and I just feel depressed about paying for heating and not getting the full benefit. It did actually used to get really hot and the heat would hit you as you came down the stairs.
The boiler, radiators and downstairs pipework was all replaced in 2020/21 but I feel its worked since then.
Does anyone know what the problem could be? I do have someone booked to come and investigate but just wondering in the meantime. 

Hi Ivy.

There are a few clues in your post. The first is that they do become hot if the other rads are shut off, but cool down again when the other rads are opened.

That tells us that the pipework to these rads is probably 'ok', so it ain't a blockage (tho' we can't rule out 'partial').  

Most likely is that the other rads are pinching the hot water from the boiler, giving it a far easier path, and the water gets returned to the boiler - thereby regulating it down - before it gets to the cool rads.

So, yes, it sounds like it needs 'balancing'.

Balancing isn't about turning other rads 'off' or down, but setting the valve on the 'other' end so that it provides what that rad needs relative to all the others.  

Each rad has two valves. One is used to control the output temp - so it'll either be a TRV (so automatic) or a 'control' valve, which you manually open and close as needed. The point is, tho', turning the other rads on and off shouldn't affect the other rads that much, since they should have been 'balanced' so that each rad only gets the 'right' amount of water in the first place. And that's where the 'other' valve comes in - the 'lockshield'. That should be set on each rad to give that rad the correct flow. So, larger rads, and rads further from the boiler, so have their lockshields tweaked open more, and the smaller and closer rads should be tweaked down. But, you need to know what you are doing. And hopefully the guy you called out will be good at this - if that is indeed the problem.

You also said you reckon these three rads could be on the same pipe feed? If so, they'll be sharing the flow, so each of their lockshields should be more open relative to the other rads. 

And that brings us on to the next interesting thing you said - the pressure dropped when you reopened the other rads. Nope, that should not happen at all.

You say you tried bleeding the rads? Did any air come out? If so, that'll likely be the cause of the drop. Hopefully, then, once you top it back up - to, say, 1.2bar - it'll now stay there.

So, monitor the pressure, and tell the guy about it. Shut off - or right down to 1 or 2 - the rads you don't actually need, like in the bedrooms during the day. 

And let us know what the guy says.

Q - do you have a magnetic filter fitted? When was it last checked? That'll tell you what state your system water is in. 

Albermarle

All the advice above is good, but just one more point.

The pump that pumps the hot water around the system normally has different speeds you can set it at.
You could try setting it at full speed to see if that helps to 'force' the hot water flow to all radiators.

IvyFlood

@Albermarle I've read on google about 'pumps' and was hoping when they come to investigate they might mention something like that.

@WIAWSNB thanks for the really detailed reply. I have no idea what I'm doing with lockshield valves so again will mention it when they come. The radiators were all bled prior to me trying to balance so I don't think its this that caused a pressure drop but I will be mentioning it. I had problems with pressure dropping in September and turned out I needed a new valve on my boiler. I know my ex husband fiddled around with all the radiators in the past so it could be they are all severely unbalanced. All my upstairs ones get nice and hot.

IvyFlood

Just been reading about lockshield valves, really interesting. I'm hoping that's the issue!

WIAWSNB

Keep an eye on the pressure, and compare cold and hot temps. Does it rise much when the CH comes on?
If you wanted to experiment with one lockshield, we can guide you. It's not only easy to do, but you can return it to its original position if it doesn't work, so not a problem.
But you can also leave it to your plumber.
If you fancy a go, then please post a pic of each valve on the hallway rad