Condensate when the boiler is not running

[Anj]

I’ve been having a few pressure drop issues with my heating system. One problem already diagnosed and sorted (thanks to this forum) was a leaking EV at the valve end (replaced) but I am still seeing a pressure drop (albeit slower than before 1.5 -1.4-1.3bar) and wanted to ask a question....

I have a Worcester 40CDi Regular this is a condensing system boiler (4 years old but previous owner maintenance very minimal if anything).
I’ve dismantled the condensate line and put a jug under.
The odd thing is even when the boiler has been not been firing for several hours it still produces condensate.
overnight boiler off at 17:30. no CH at all (which i have valved off anyway)
no water cylinder heating until 07:45 but when I checked at 07:30 before the boiler fired the condensate jug was overfilling (so more than 0.5litre) but the boiler hadn’t fired at all and was showing 16degC (it’s in the garage). The pressure was down by ~0.5bar

so again boiler was off after the morning water heating enidng at 08:30. Waited an hour and then replaced the jug. At 10:30 the jug was empty but by 1600 it was overfilling again (temp 20degC) and Boiler wasn’t due to fire until 16:45.

So the question is should a condensing boiler be creating condensate when it hasn’t fired??

I am 99% sure the answer is no, but just wondered if because the boiler was on electrically could it make a difference? I don’t see how... doesn’t condensate only come from the boiler firing?

The condensate line is standard drop/gravity based (there is no pump or anything on the line).

Am just thinking could it be the HX is letting by?
There is also a manual valve inside the boiler by which the boiler can be emptied straight to condensate line - could that be leaking?
Or is what I described normal?
I could turn the boiler off electrically but I don’t see what difference that makes.

The condensate isn’t a constant trickle all the time it seems to batch the condensate in glugs so for an hour or so nothing, then a dump of water, then trickle from the dump then another dump - I’ve read elsewhere that the Worcester does “batch” the condensate but not sure if that is true?

really appreciate any thoughts or comments.

 

[EvilDrPorkChop]

Sounds like your HEX has a leak internally which is draining down the condensate - it's not uncommon but can be easily missed. I'm guessing there is no way to isolate the boiler from the system due to it being a regular heat only boiler rather than the system version (this has valves underneath you can isolate).

 

[SJB060685]

As above. Condensate is a by product of the combustion process, if the boiler is not running then its not going to condense. The fact you say your system is losing pressure during this time reinforces the possibility of a leaking HEX.

 

[Anj]

Sounds like your HEX has a leak internally which is draining down the condensate - it's not uncommon but can be easily missed. I'm guessing there is no way to isolate the boiler from the system due to it being a regular heat only boiler rather than the system version (this has valves underneath you can isolate).

I can isolate the return as there are 1/4 ball valves for the magma clean which is the last thing in the return.
The pump is directly underneath the flow but that has gate valves which I am told by folks here are rubbish and do not reliably seal so I’d never really know. (I am changing (ordered) all the other valves to ball valves as a result of advice I have been given on this forum).
The pressure gauge(s) however are on the system side so I can’t really isolate the boiler and see the pressure drop in the boiler. I could try to isolate the boiler and see if the pressure holds and the water is still collected but the darn gate valves on the pump will always leave a doubt?
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As above. Condensate is a by product of the combustion process, if the boiler is not running then its not going to condense. The fact you say your system is losing pressure during this time reinforces the possibility of a leaking HEX.

Thanks. Good to have two concurring opinions. It’s still on warranty so I’ll get Worcester out to have a look.

 

[SJB060685]

I can isolate the return as there are 1/4 ball valves for the magma clean which is the last thing in the return.
The pump is directly underneath the flow but that has gate valves which I am told by folks here are rubbish and do not reliably seal so I’d never really know. (I am changing (ordered) all the other valves to ball valves as a result of advice I have been given on this forum).
The pressure gauge(s) however are on the system side so I can’t really isolate the boiler and see the pressure drop in the boiler. I could try to isolate the boiler and see if the pressure holds and the water is still collected but the darn gate valves on the pump will always leave a doubt?
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Thanks. Good to have two concurring opinions. It’s still on warranty so I’ll get Worcester out to have a look.

If its still under warranty then that's your first call!
Even if you managed to isolated boiler, without the pressure gauge on that side of the system then you won't see the pressure stable or drop anyway.
PS. Pump valves are notorious for weeping after you've fiddled with them. Some people like to re pack them to stop any weeps, we however always replaced.

 

[EvilDrPorkChop]

I can isolate the return as there are 1/4 ball valves for the magma clean which is the last thing in the return.
The pump is directly underneath the flow but that has gate valves which I am told by folks here are rubbish and do not reliably seal so I’d never really know. (I am changing (ordered) all the other valves to ball valves as a result of advice I have been given on this forum).
The pressure gauge(s) however are on the system side so I can’t really isolate the boiler and see the pressure drop in the boiler. I could try to isolate the boiler and see if the pressure holds and the water is still collected but the darn gate valves on the pump will always leave a doubt?
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Thanks. Good to have two concurring opinions. It’s still on warranty so I’ll get Worcester out to have a look.

Gate Valves as you said aren't always reliable to get a perfect seal, although I wouldn't go unnecessarily replacing them all in your system because of this.

Regarding the pressure gauge though - if you did close both pump valves and the Magnaclean valves and assuming they all sealed closed correctly then on reopening the valves if the boiler has leaked you would see your system pressure decrease; also before reopening you should see you system maintain it's pressure if it's the boiler (As this will have been isolated from the system).

You need to get Worcester out under warranty, however I suspect they will want some proof it's the HEX before replacing it - especially under warranty.

 

[Anj]

Gate Valves as you said aren't always reliable to get a perfect seal, although I wouldn't go unnecessarily replacing them all in your system because of this.

Regarding the pressure gauge though - if you did close both pump valves and the Magnaclean valves and assuming they all sealed closed correctly then on reopening the valves if the boiler has leaked you would see your system pressure decrease; also before reopening you should see you system maintain it's pressure if it's the boiler (As this will have been isolated from the system).

You need to get Worcester out under warranty, however I suspect they will want some proof it's the HEX before replacing it - especially under warranty.

How would I prove it’s the HEX then?
The engineer would need to be here for 8 hours or so to see the condensate “jug” fill up?

one of the reasons I was going to replace the other gate valves that isolate the central heating system was so the Bosch engineer wouldn’t fob me off with “gate valves are leaking and the there is another leak in the system somewhere”.

 

[SJB060685]

How would I prove it’s the HEX then?
The engineer would need to be here for 8 hours or so to see the condensate “jug” fill up?

As DrEvil suggested. If you isolate one of the magnaclean valves and one pump valve this is effectively isolating the boiler. Top up the system first and then do that. If like he said you hear a rush of water when you reopen them then thats a good sign it was leaking and the jug of water will confirm that. I should of gone in to more detail and I apologise.
If you proved that first before they arrive thats good ground to start on.

 

[Anj]

As DrEvil suggested. If you isolate one of the magnaclean valves and one pump valve this is effectively isolating the boiler. Top up the system first and then do that. If like he said you hear a rush of water when you reopen them then thats a good sign it was leaking and the jug of water will confirm that. I should of gone in to more detail and I apologise.
If you proved that first before they arrive thats good ground to start on.

Got it. Will do. Thanks a lot for the advice

 

[SJB060685]

Got it. Will do. Thanks a lot for the advice

Obviously make sure the boiler is electrically isolated at switched fused spur. You don't want the burner igniting

 

[Anj]

Obviously make sure the boiler is electrically isolated at switched fused spur. You don't want the burner igniting

Yes. Thanks again. Much appreciated.

 

[John.g]

I’ve been having a few pressure drop issues with my heating system. One problem already diagnosed and sorted (thanks to this forum) was a leaking EV at the valve end (replaced) but I am still seeing a pressure drop (albeit slower than before 1.5 -1.4-1.3bar) and wanted to ask a question..

I have a Worcester 40CDi Regular this is a condensing system boiler (4 years old but previous owner maintenance very minimal if anything).
I’ve dismantled the condensate line and put a jug under.
The odd thing is even when the boiler has been not been firing for several hours it still produces condensate.
overnight boiler off at 17:30. no CH at all (which i have valved off anyway)
no water cylinder heating until 07:45 but when I checked at 07:30 before the boiler fired the condensate jug was overfilling (so more than 0.5litre) but the boiler hadn’t fired at all and was showing 16degC (it’s in the garage). The pressure was down by ~0.5bar

so again boiler was off after the morning water heating enidng at 08:30. Waited an hour and then replaced the jug. At 10:30 the jug was empty but by 1600 it was overfilling again (temp 20degC) and Boiler wasn’t due to fire until 16:45.

So the question is should a condensing boiler be creating condensate when it hasn’t fired??

I am 99% sure the answer is no, but just wondered if because the boiler was on electrically could it make a difference? I don’t see how... doesn’t condensate only come from the boiler firing?

The condensate line is standard drop/gravity based (there is no pump or anything on the line).

Am just thinking could it be the HX is letting by?
There is also a manual valve inside the boiler by which the boiler can be emptied straight to condensate line - could that be leaking?
Or is what I described normal?
I could turn the boiler off electrically but I don’t see what difference that makes.

The condensate isn’t a constant trickle all the time it seems to batch the condensate in glugs so for an hour or so nothing, then a dump of water, then trickle from the dump then another dump - I’ve read elsewhere that the Worcester does “batch” the condensate but not sure if that is true?

really appreciate any thoughts or comments.

You say that you have put a jug underneath the drain, in that other thread you said -"--- however it can dump water direct to the condensate line through a manual valve--" so just be happy that the jug is actually monitoring the Hx condensate out and nothing else.

 

[Anj]

You say that you have put a jug underneath the drain, in that other thread you said -"--- however it can dump water direct to the condensate line through a manual valve--" so just be happy that the jug is actually monitoring the Hx condensate out and nothing else.

Yes John.G..... the design of the boiler means that both the manual dump valve and the condensate both come out the same line (the two opaque rubber pipes connect together inside the boiler). There is no way for me to actually know if the HEX is leaking or the manual valve is letting by. I think that part I have to leave to the Bosch chap?.

In theory I could undo the hose for the manual valve but I’d rather not mess about with anything inside the casing (other than looking at it) not only in case it goes bang but in case I invalidate the warranty. My thinking is in either case Bosch needs to fix it.
Thanks for the post.

 

[John.g]

Also, pressure dropping from 1.5bar to 1.3bar would indicate a leakage of 2.5 litres, a fair drop.

 

[SJB060685]

Yes John.G... the design of the boiler means that both the manual dump valve and the condensate both come out the same line (the two opaque rubber pipes connect together inside the boiler). There is no way for me to actually know if the HEX is leaking or the manual valve is letting by. I think that part I have to leave to the Bosch chap?.

In theory I could undo the hose for the manual valve but I’d rather not mess about with anything inside the casing (other than looking at it) not only in case it goes bang but in case I invalidate the warranty. My thinking is in either case Bosch needs to fix it.
Thanks for the post.

So both the PRV and condensate discharge both terminate in the same discharge point?
If that's the case you failed to mention that above.
You changed the expansion vessel so let's assume its of adequate size and charged correctly, i would still isolate the boiler as we discussed before and don't run the boiler. If the boiler drains its either a leaking HEX or the PRV is letting by. To prove one or the other i would separate the PRV discharge hose and hang in a bowl