Boiler - acting strangely

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Hello,

I've spent quite a long time trying to research possible solutions to my current boiler problem online but haven't been able to find anything.

Our heating system is an open vented - gravity fed system with header tank in loft and hot water tank in airing cupboard. Conventional boiler downstairs - Ideal Classic 240FF.
Circulation pump - Myson compact.

We've been having our integral garage (where boiler is located) converted.

A new radiator was added.

The system was drained twice during installation. Once to add the pipes. Then again a few days later when the radiator was put in.

The first time, we weren't getting any hot water.

I bled the hot water tank of air via the valve next to it, and that fixed the problem, back to normal.


The second time - radiators weren't working properly. Thorough bleeding of the radiators got the cold ones working again - the new radiator was heating, just taking longer than the others. May have to balance them.


However, there's an issue or two with the boiler and hot water.


The boiler will not fire up if the thermostat is set to less than about 5 1/2 (out of 6)
If I turn it lower than that it clicks off. it will not relight thereafter - this led to us having a morning with no hot water in the tank as I hadn't realised, it had seemed to be working when set to 4, but wouldn't come back on in the morning on 4.

The second issue - although it may well be the same - even if the boiler is on, it is not staying on for very long.

Say I've got it set to be on for hot water for an hour - it fires up once every twenty minutes. It only stays on for a very short time when it does fire up.

The water is not getting heated fully. It's coming out of the taps and shower warm, but not hot. It's a consistent temperature - but lower than it was before.

I've increased the temp on the Hot Water cylinder thermostat but that's made no difference.


However it's working fine for the central heating! Was heating the radiators no problem and staying on for the sort of length of time you'd expect.

It just seems to be a problem with the hot water - I've bled the pump and the hot water tank again - although there's no air coming out at all. It's throughly bled. The hot water is getting through to the tank...the issue seems to be that the boiler just isn't staying on for long enough to get enough hot water going.

Any ideas what it could be?

It was working fine before the radiator was added - that includes in the space of time between the pipes being added and the radiator being added. Nothing has been done with the boiler, it's in the same position it was. As I said the central heating is working fine. Its just that the hot water Doesn't seem to be heating up fully and the boiler isn't wanting to work when set at anything other than max on it's thermostat.

Apologies for long post - wanted to give as much info as possible!

Thank you
 
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It is air locked by the sound of it. Try filling the system with a hosepipe connected to the draincock.

Welcome to the world of 'but it is only a simple job'
 
Think I would start with a new boiler thermostat, have you bled the pump ?
 
It is air locked by the sound of it. Try filling the system with a hosepipe connected to the draincock.

Welcome to the world of 'but it is only a simple job'

Thanks, is it possible to do thus by connecting the hot and cold appliance outlets (under kitchen sink) together with a washing machine hose pipe?

Read something like that online.

I'd discounted airlock, purely as I'd bled everything I could and I don't have any blocked taps or anything.

It's worth a try though. I'd read something about needing to be careful and not pump too much mains water through the system as could overflow in header tank? Maybe need to wait til I can get a second person to be in the loft to shout stop!
 
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No ,that won't work. Do you have a drain cock outside or on a nearby radiator?
 
You have an air bubble in the coil of the gravity circuit on the cylinder. I have seen this loads of times. Try draining and refilling again. There is a method to clear the bubble but it involves overriding the safety controls and I don't want to be held responsible if it goes wrong....
 
Thanks for that HootingOwl. I've had a proper look at it today with my father and we came to the same conclusion.

The water pipe coming from boiler was intensely hot. The return pipe was only room temp.

Following up to the hot water tank, again the heating pipe going in was hot, the one on the way out only lukewarm.

We drained water out of the draincock on the return pipe to boiler and did get some air out. But it hasn't shifted it. The water is warmer a tad, but it's definitely still not working properly.
 

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