More boiler / heating issues

[Symposium]

Posting again as the responses to my previous boiler issue were very helpful. I've had a new expansion vessel fitted, boiler pressure has been stable. Had a mini service from British Gas since then, when signed up to Homecare, that found no issues . However, when putting on the central heating now 3 radiators are staying stone cold . 5 are boiling hot. Have checked the obvious things like the thermostatic valves are open. Puzzled as to why just 3 . Is there any thing else I can try before I call them out again?

When this has happened to me it has always been the bit below the valve is stuck so the actual valve that you turn looks open but it isn't working anything underneath it.

I have also found that if you have BG out a lot, then the cost of next years Homecare goes up a lot, bit like car insurance, just so you are aware.

This sounds like air blockages. Presumably when you had the expansion vessel changed they drain the system ?

Often engineers then leg it without checking the entire system is up and running correctly because they are under a lot of time pressure. It can be quite hard to refill a system correctly removing all the air sometimes.

Google it and there will be some tips. I found bleeding the radiators repeatedly did it. I bled one day and removed all the air. Then ran, waited a couple of days and then bled again. It takes a few days of running, but eventually all the air finds its way out to the tops of the radiators where it can be bled. Remember you will need to repressurise to replace the lost air.

First thing is to bleed all the radiators. Second thing I would do if this doesn’t fix it is shut all the valves and then open one of the problem radiators to see if it heats up. If so then you need to go around and balance the system which might have been overlooked / not done if you had a new system. Are the three radiators that don’t work upstairs/ downstairs or both?

Thanks for all the help, it's 3 radiators at the front of the house. 2 upstairs and 1 downstairs. The ones that work are all towards the back of the house. I will definitely try bleeding them. Do I need to do all 8 or just the 3?

I'm worried about the premium increases so if I can fix myself without calling them that would be great!

As others have said Bleed all the air out first( if any ). I would shut the radiators off that are getting hot , this should get the others hot so you know they work. If the others don’t get hot then i would say the valves are stuck/ seized.

if they do get hot when the others are turned off but go cold when you turn them back on then its a case of the system needs balancing. You can youtube how to do it, its a simple process but just takes time to get it right 👍

I've tried bleeding the radiators, no air came out of any of them. I've looked up balancing and started by turning the valves of the hot radiators off. Doing this I did start to feel a little warm coming into 1 of the cold radiators upstairs. However, the boiler simply will not stay on. It's just turned itself off as it the temp has reached. The thermostat is set high at 25, current temperature is 20, heating is definitely on but the boiler will not fire up!

Sorry that should read as if the temperature has reached. I can't understand why it's turning itself off . Pressure is ok .

If you’ve got all the radiators shut off then the system will heat up and switch off quicker. What state is it all in at present? Pick one of the cold radiators. Turn all of the other seven off at both sides - both the flow and return. Does the cold radiator now warm up?

Not having much luck. I've managed to turn off 5 both sides. There are 2 that I can't turn off, 1 upstairs and one downstairs dues to having old valves, these are not the problem ones . I tried running the heating and these 2 are hot and the 1 cold one I left open is a teeny tiny bit trying to get warm, but pretty much still cold. Boiler has turned itself off again.

This is useful for sticky valve pins from about 3 minutes 40s (other sticky valve videos are available).

Thanks but I think I'm going to have to admit defeat and call them out. Nothing I'm trying is having any effect. I'm a bit worried I might have made it worse fiddling with the return valves.

Your problem is likely to be related to British Gas IME. We cancelled our maintenance contract with them because every time they came out to fix something they either didn't have the right part, fitted the wrong part, or broke something else. Then they would demand more money because I was calling them out too often. I found a local company and they are very good.

When did this problem arise, ie was it immediately after expansion vessel issue or after BG gave a service, or since. If it's one of the first two, then I'd say go back to whoever did that repair/service as it sounds like they've done something to the system so it's not balanced correctly.

If the rads and system are quite old then it could be a sludge build up. Is the cold rad cold all the way through or only at the bottom? You could flush the rads but I suspect that isn’t something you’ll be able to tackle DIY - it is an easy enough job and you can replace the stuck valves at the same time but you’ll need to drain down the system / bung the tank depending on what you have.

How long is the boiler staying on for? If only a few moments then could be ignition issue. If long enough to heat up the two rads you say are getting hot then it’s likely it is cycling due to heating the water sufficiently and then shutting down. If your DIY skills only stretch as far as turning the valves on and off (no offence intended) then you are likely already at the extent of what you can feasibly do so you may as well call them out.

Actually now you say that, before this issue the radiators were only getting hot at the top and were cold at the bottom. I was starting to think about there being a sludge issue and then forgot about it. The 3 affected radiators are definitely completely cold now. The boiler is staying on for about 10/15 minutes then turning off. The 5 unaffected radiators are boiling hot in that time. But the 3 others stone cold. You are right that my diy abilities are limited. I like to have go if I can but only if I think I can really manage it. Clearing out sludge is a bit beyond me! Thanks for the suggestions though.

We had our boiler changed two years back and the installer didn’t do a flush or power clean. There’s certainly no guarantee an installer will flush the system unless you pay for it. I ended up replacing a load of my radiators anyway and the ones I took off were properly gunky.

Boiler is quite old... I think around 17 years 😫 it does have one of those filters I believe. We only moved in to this house around 3 years ago so have just wanted to keep things ticking over as long as possible before replacing. We've spent a small fortune on new windows, rendering, roofing etc. so we're just hoping the heating system could wait a bit. We've had it serviced regularly and they've done a few little repairs and told us we may as well keep it going as it's generally a good boiler.

Yeah the bloke was a bit of a cowboy to be fair - disappeared once paid with our boiler warranty card. Worcester were ok with it and it’s now had two yearly services and the engineers haven’t turned up and gone oh my god which clown did this, so it must have been installed ok at least. Not sure there is a requirement to powerflush a system for warranty, I think it’s just clean which could be mains pressure. The OP saying the system is about 17 years introduces the possibility certainly that there could be sludge build up.

I can see this thread is a couple of days old; did you get it fixed? I'd look at the pump, they loose their oomph.
The farthest radiators losing their heat whilst others are not plus the boiler cycling on & off would be an indication that it's not moving the heat from the boiler as efficiently as it should.

No it's not fixed yet. I've just adopted a rescue cat and I can't face having to deal with a workman in the house yet. You've just reminded me that when we got back from holiday a couple of weeks ago, the boiler briefly displayed a pump fault code but it disappeared again. It's since had a mini service and I told the engineer but he didn't seem to think it significant and didn't find anything wrong. I didn't realise about the cold radiators at that point. After all it's been warm and we haven't really needed the heating. I'm going to call them out soon but as we still have hot water I'm not in a rush.