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[Sir Tigger KC]

Yes this one's had 3 PCB's and a 3 way valve, which I don't think is bad for a 23 year old system. 

Bout time you bought a new boiler then.....a quick google on your boiler shows its only about 70% efficient 
But I guess it depends how long you intend to live in the property 

Have you sorted the problem?

If it was 70% inefficient I'd think about it...   

Well I managed to get one of the draincocks flowing today and thankfully without any mess!    It drained down and filled up again with no problems, so we can rule out a blocked feed pipe and I fitted new washers to all 3 draincocks.   

Unfortunately it seems to be operating much the same as before.    I've bled all the rads a couple of times and they're all getting nice and hot, but there is still air gurgling and the boiler keeps shutting down and restarting. 

The pump has been mentioned a couple of times and I'm wondering about this now.  Although its obviously working as the rads are all getting hot, it did make a horrible whirring sound when I first switched the system back on and I'm wondering if it's sticking from time to time. 

[Andy H]

Well I managed to get one of the draincocks flowing today and thankfully without any mess!    It drained down and filled up again with no problems, so we can rule out a blocked feed pipe and I fitted new washers to all 3 draincocks.   

Unfortunately it seems to be operating much the same as before.    I've bled all the rads a couple of times and they're all getting nice and hot, but there is still air gurgling and the boiler keeps shutting down and restarting. 

The pump has been mentioned a couple of times and I'm wondering about this now.  Although its obviously working as the rads are all getting hot, it did make a horrible whirring sound when I first switched the system back on and I'm wondering if it's sticking from time to time. 

I suspect that the gurgling noise is due to pockets of air that have collected in the radiator pipes over the summer. Each time the flow stops they go bubbling back up to high level. If you can get the system to run normally they should find their way back to the header tank or into the radiators.

The question is why does the flow keep stopping? likely causes are sticking pump, faulty 3 port valve (or the switches in it) or the room thermostat.

[Sir Tigger KC]

I suspect that the gurgling noise is due to pockets of air that have collected in the radiator pipes over the summer. Each time the flow stops they go bubbling back up to high level. If you can get the system to run normally they should find their way back to the header tank or into the radiators.

No I don't think so as a) I've had the system running OK since the summer and b) I've drained down, refilled and bled the system.  What I don't understand is why this air isn't venting off as it sounds like large amounts, so it's more of a gurgling/glugging noise than bubbling and only around the boiler/hot water cylinder. 

There's a automatic vent tee'd onto the return feed just above the boiler and I did wonder if that has failed and is sucking air into the system, but I screwed the cap down tight and there was no difference and when I unscrewed the cap a small amount of air hissed out.

The question is why does the flow keep stopping? likely causes are sticking pump, faulty 3 port valve (or the switches in it) or the room thermostat.

The pump is seems to be whirring away nicely when the boiler stops, but I think when you remove the bleed screw you can see the impeller?  I'll check that later.

The 3 way valve was changed about 3 years ago, but this is a possibility as the glugging/gurgling sound is much worse when in Heat/Hot Water Mode, than in Heat or Hot Water only.

I think the roomstat is OK as it seems to operate normally.  So when it's at 30 degrees the boiler tries to run continuously, but turn it down to 18 degrees it dosn't try to run so much.

Thanks for the replies! 

[Kevin Wood]

Can you get to the pipework out of the top of the boiler?

If the flow is stopping, I'd expect it to be really hot near the boiler but for the pipes further away to start cooling off. If they all stay the same temperature throughout, you have some flow.

Also, new air will be introduced with the fresh water, so expect to have to bleed it regularly for a while.

In fact, one possibility is that it has a leak, so new water is constantly being added to the system, bringing air with it, although I would expect it to work OK for a while after filling.

Air leaking in to a low pressure point in the system might be a possibility. In fact, the location of that automatic bleeder sounds suspect, as they can admit air if they don't have positive pressure on them all the time. Sounds like that might have been added as an afterthought when it wouldn't bleed properly after commissioning?

[TD]

Can you get to the pipework out of the top of the boiler?

If the flow is stopping, I'd expect it to be really hot near the boiler but for the pipes further away to start cooling off. If they all stay the same temperature throughout, you have some flow.

Also, new air will be introduced with the fresh water, so expect to have to bleed it regularly for a while.

In fact, one possibility is that it has a leak, so new water is constantly being added to the system, bringing air with it, although I would expect it to work OK for a while after filling.

Air leaking in to a low pressure point in the system might be a possibility. In fact, the location of that automatic bleeder sounds suspect, as they can admit air if they don't have positive pressure on them all the time. Sounds like that might have been added as an afterthought when it wouldn't bleed properly after commissioning?

IIRC that was the location of a bleed valve (but a manual one) on my old system. When I added a cleaner to the system it was always the point where most of the air came out. Could the automatic bleeder be getting old and sticking and not releasing the air? Is there a way to manually release the valve?

[Sir Tigger KC]

No I've heard air coming out of the valve, unless it's sucking in.    As to the location, it's on the highest point of the system apart from the F/E tank and pipework, but then if the pump is sticking maybe it is drawing air in when the pump sticks and the pressure falls away.    However I have screwed the cap down tight and it makes no difference. 

But what I still don't understand is why all this air isn't venting out through the feed pipe to the vent over the F/E tank.  It's not just a few bubbles trickling around it's a lot of air!   

[STEMO]

No I've heard air coming out of the valve, unless it's sucking in.    As to the location, it's on the highest point of the system apart from the F/E tank and pipework, but then if the pump is sticking maybe it is drawing air in when the pump sticks and the pressure falls away.    However I have screwed the cap down tight and it makes no difference. 

But what I still don't understand is why all this air isn't venting out through the feed pipe to the vent over the F/E tank.  It's not just a few bubbles trickling around it's a lot of air! 

If you'd have called a heating engineer, you'd have been warm and toasty now...like wot I am 




Or.....



He'd have condemned the boiler and you be sitting looking at a load of labels saying "DO NOT USE". 

[Sir Tigger KC]

He'd have condemned the boiler and you be sitting looking at a load of labels saying "DO NOT USE". 

This I expect!   

Any way in other news I fixed the dishwasher this afternoon! 

[TD]

No I've heard air coming out of the valve, unless it's sucking in.    As to the location, it's on the highest point of the system apart from the F/E tank and pipework, but then if the pump is sticking maybe it is drawing air in when the pump sticks and the pressure falls away.    However I have screwed the cap down tight and it makes no difference. 

But what I still don't understand is why all this air isn't venting out through the feed pipe to the vent over the F/E tank.  It's not just a few bubbles trickling around it's a lot of air! 

If that were the case, then it would be drawing air in when the system was off or room stat shut the heating off, so unlikely imo.
Does it make any difference if you close the bypass valve? I'm thinking maybe the air is just circulating around the boiler, thro the bypass. Its perfectly safe to shut off the bypass valve as long that you make sure at least one rad thermostat is fully open (if you have them, if you don't then it doesn't matter if you shut of the bypass valve as long as the rads are turned on)
If the bypass is closed it might force the air to another part of the system which can be bled 

[Sir Tigger KC]

No I've heard air coming out of the valve, unless it's sucking in.    As to the location, it's on the highest point of the system apart from the F/E tank and pipework, but then if the pump is sticking maybe it is drawing air in when the pump sticks and the pressure falls away.    However I have screwed the cap down tight and it makes no difference. 

But what I still don't understand is why all this air isn't venting out through the feed pipe to the vent over the F/E tank.  It's not just a few bubbles trickling around it's a lot of air! 

If that were the case, then it would be drawing air in when the system was off or room stat shut the heating off, so unlikely imo.
Does it make any difference if you close the bypass valve? I'm thinking maybe the air is just circulating around the boiler, thro the bypass. Its perfectly safe to shut off the bypass valve as long that you make sure at least one rad thermostat is fully open (if you have them, if you don't then it doesn't matter if you shut of the bypass valve as long as the rads are turned on)
If the bypass is closed it might force the air to another part of the system which can be bled 

No bypass valve. 

[Andy H]

Any strainers in the system?

[Sir Tigger KC]

Any strainers in the system?

Erm?    What are those?   

[Andy H]

Any strainers in the system?

Erm?    What are those?   

A mesh basket in the pipe to catch bits of crud.

It is unlikely that you will have one in a 15 year old domestic heating system but modern boilers might have one.

The commercial systems that I spend most of my time working with have lots of strainers and it can cause all sorts of grief when they block up......

[Sir Tigger KC]

Any strainers in the system?

Erm?    What are those?   

A mesh basket in the pipe to catch bits of crud.

It is unlikely that you will have one in a 15 year old domestic heating system but modern boilers might have one.

The commercial systems that I spend most of my time working with have lots of strainers and it can cause all sorts of grief when they block up......

Ah yes, no nothing like that.

The pump is OK though, I popped off the bleed screw and watched for a while and it doesn't stick or stop when the boiler shuts down.   

[TD]

He'd have condemned the boiler and you be sitting looking at a load of labels saying "DO NOT USE". 

This I expect!   

Any way in other news I fixed the dishwasher this afternoon! 

Good news on that front then  Would you like to pop round and fix mine then 

Actually I know whats wrong with it.....and its either £80 for the new part or a new machine