Gas smell from boiler when it switches off.

[Dan Robinson]

I know how frustrating it can be working with people who know less than you but this really isn't an acceptable way to behave towards them. If you don't want to help, don't but don't just sit around being insulting towards them. As you say, you've been in the industry for over 36 years and the OP is a DIY-er. You'll obviously know more than him - that's why he's here asking questions.

Perhaps you should have a reread of this thread.

 

[penguin16]

Perhaps you should have a reread of this thread.

Oh I have - it's mind numbingly boring stuff - it still doesn't really warrant such personal abuse towards him.

 

[Mikefromlondon]

But the turret seal or the cover seal must also be defective. My background is pressure testing oil industry equipment and the design of clipping the boiler casing cover on top and bottom just doesn't seem very great to me. If the casing seal is so significant from a safety point of view I think it should have more fixing points round the whole perimeter of the casing to ensure the seal is contacted all the way round.

I agree with you on the cover being held on by clips alone, a bit like my Vaillant VCW GB 221, which has a cover that is clipped at the top and just 3 screws to hold it in position, and by now 22years into service the seal must have become hardened and depressed such that it is no longer making a perfect seal, and on a boiler that is balanced flue where there is no fan assistance to remove products of combustion, but touch wood, so far so good my CO detectors haven't yet gone off. They are on a standby just in case.

by the way, CO is never emitted on its own in its pure form, it is part of the product of combustion and so if you can smell other products of combustion then it is safe to surmise that you are also getting some amount of CO as well. How much Co, this depends on how well your boiler's combustion is, on mine it is 1 part per Million, when it was recently analysed by an RGE.

 

[Restoration man]

No idea why I've been labeled a time waster or a tosser. Find it bizarre that trade folk who are good enough to give up there time on here for advice get so wound up.

My story hasn't changed. I have provided updates as things have happened and answers to questions I've been asked.

For those interested the summary is as follows:

Boiler was serviced. Sump removed during service due to a small condensate drip the boiler had since last service. We were told everything was perfect when he left.

About 4 weeks later came home to CO alarms going off.

Mains gas eng checked meter to boiler supply. All ok. No CO. No CO alarm explanation.

Service eng came out. No faults found. Suggested changing burner and gasket.

Service eng took off burner which was refitted with new gasket. New burner not required.

Stink of combustible products (just for you ianmcd) next day. No CO alarm. The CO alarms have never gone off again!

Service engineers came back tested everything ok. No reason found for combustible products smell. Told to reuse boiler.

Smell again service engineers came back tested everything ok. No reason found for combustible products smell. Told to reuse boiler.

Smell again. Figured out ourselves this smell only happened 10 to 20 minutes after the boiler had gone off.

Called Ideal. They wouldn't discuss with me and we're duty bound to call out mains gas eng again.

Mains gas eng revisited. All checks up to boiler ok.

Original service engineer who did the boiler service turned up. Was concerned about the sump he'd removed. Removed sump. Found damaged sump seal. Replaced sump seal.

So far since yesterday no further combustible products smell which is good.

Down side is the combustible products which appear to have been leaking from the sump gasket must also have been leaking out from the boiler casing.

No tests from the mains gas eng or the service eng ever detected anything from outside the casing.

So potentially casing seal sometimes seals when's it's been off and refitted and sometimes doesn't. Or never seals but there was no leak when the service engineers were actually here testing.

Could change casing seal but I'd want to be able to positively test the current one doesn't hold and confirm a new one once fitted does. I don't know if that is possible.

Thanks

 

[Mikefromlondon]

I think you have made it clear enough that it was your damaged sump gasket, so your GSEngineer replaced it and now the problem is gone, but if you are talking about an outer cover, on many boilers like mine it is not a gas tight seal, it is just a cover to protect gubbings, yours may have a secondary seal, but clearly that failed in your case, since your CO detectors went off. The cover I was talking about on my vaillant boiler is the cover on its combustion chamber, that in is a crucial component and to keep POC well away from leaking back into the house. Having a room sealed balanced flue means there is no means of extraction of POC to outside as it relies on convection currents, so there is no negative pressure and under drafty conditions the POC can leak back into the house through a poorly sealed cover. Another version of a similar boiler later on had a fan added to it, I am not sure what the heck it is called but yes an improvement i would say.

 

[Mikefromlondon]

One day I was doing a BBQ in my garden and it suddenly started to pour down! so i collected my BBQ charcoal grill , it is smallish and round bought it from Lidl it looks like a Sputnik Russian spacecraft sliced in half horizontally! and so thought let me take it in the Kitchen place it over my cooker hob, under the cooker hood and turned my extractor fan full on, within about 5 minutes my CO detector went off, I had to call off my BBQ! Should there be strict regulations regarding BBQs and remember a couple of people died in their tents when they went camping and were doing BBQ with a portable grill.
A bit like this: https://encrypted-tbn1.gstatic.com/...UU7BwH7RJKDgM5JjLa89THgXnt8QqhOVpwd5NThe557mQ

 

[ollski]

One day I was doing a BBQ in my garden and it suddenly started to pour down! so i collected my BBQ charcoal grill , it is smallish and round bought it from Lidl it looks like a Sputnik Russian spacecraft sliced in half horizontally! and so thought let me take it in the Kitchen place it over my cooker hob, under the cooker hood and turned my extractor fan full on, within about 5 minutes my CO detector went off, I had to call off my BBQ! Should there be strict regulations regarding BBQs and remember a couple of people died in their tents when they went camping and were doing BBQ with a portable grill.

If you go on the hse website and look at co deaths there are usually more camping / bbq fatalities than gas / woodburning appliances

 

[Mikefromlondon]

You truly are an idiot.

No you don't have to call me an idiot and what if I call you a fool how would you feel? I consider myself to be adventures and forward thinking & challenging person taking on things others would just turn around and back off.

Thought you might have got a better idea by suggesting that i could have used a brolly! But you lack imagination, sadly you are not that smart arse I thought you were!

 

[bernardgreen]

Having a room sealed balanced flue means there is no means of extraction of POC to outside as it relies on convection currents, so there is no negative pressure and under drafty conditions the POC can leak back into the house through a poorly sealed cover. Another version of a similar boiler later on had a fan added to it, I am not sure what the heck it is called but yes an improvement i would say.

Room seals have to take into account situations where the air pressure outside the building in the area of the flue terminal is considerably higher than the air pressure inside the building. In the fan sucks directly from the air intake and not from the room sealed interior cavity of the boiler the outside / inside pressure differential does not affect the room seal.

If the fan does suck air from the room sealed cavity which is connected to the outside via the air intake then the room seal has to be able to withstand the outside / inside pressure differential and not leak under any waether conditions ( gales blowing directly onto the flue terminal ).

Not well worded and no doubt "experts" will have their opinions.

 

[Agile]

Maybe the experts know how boilers work?

In reality the air intake goes to the inside of the boiler and circulates around the area and cools the components.

It does not go directly to the burner!

That is why no further compartment ventilation is required on most modern boilers.

Tony

 

[Mikefromlondon]

In other words, manufacturer's have found a way to create revenue,

Room seals have to take into account situations where the air pressure outside the building in the area of the flue terminal is considerably higher than the air pressure inside the building. In the fan sucks directly from the air intake and not from the room sealed interior cavity of the boiler the outside / inside pressure differential does not affect the room seal.

If the fan does suck air from the room sealed cavity which is connected to the outside via the air intake then the room seal has to be able to withstand the outside / inside pressure differential and not leak under any waether conditions ( gales blowing directly onto the flue terminal ).

Not well worded and no doubt "experts" will have their opinions.

Yes I know Bernard, it sucks!

what I also meant by having no negative pressure inside a combustion chamber, or its associated flue system, a fan would create a slightly low pressure such that air and POC are sucked out of the combustion chamber and fresh air continues to be is drawn in, into the system and therefore any gasses within the CC will have no chance of escaping or popping out of your cover seals, at worst if your cover seals were leaky, they would actually draw air into the system rather than push out any through the leaky seals, therefore a fan guarantees this as well as helps avoiding any explosion from any raw gas that may start accumulating if not drawn out that could otherwise get ignited with bad consequences.

On my vaillant VCW221 Gb boiler it does not have a fan as it uses a permanently lit pilot flame to avoid raw gas accumulating, it has to flame monitoring device called a thermo-couple to switch gas valve off if the flame died, as it often does from time to time, though very very rarely. As far as I know my thermo-couple has only ever gone off a dozen or so times in its 22 years service and is still the original as it has never been replaced by anyone to my knowledge. My RGE don't even tinker with it accept when they are conducting a full service every few years when they may clean the tip of it. It has been serviced recently and I was there and saw it for myself, RGE commented how good these boilers are and newer ones need regular service due to condensate problems.

I also believe in some boilers the air is sucked in rather than sucked out, if forcing air into the boiler, it creates a positive pressure rather than a negative, so the forced air is pushed through the system and out through the CC, and then into the exhaust flue rather than being sucked out , so where the air is drawn in by a fan, and forced to go through CC, to be pushed out, there are more chances of a poorly made seal allowing air and perhaps other POC to escape into the room ..

 

[tayzyboy]

Hi Restoration man,
Did you get to the bottom of this ever?
I have a very similar issue with my worcester boiler. emergency gas man came out, smelt the gas, but nothing detected on his instruments.
Gas smell only comes once boiler has switched off after a prolonged heating period.
Gas smell clears after opening window for a few mins.
Had an engineer out for a full service, heating elements and case seal.
Still occuring.
Any things you could suggest would be greatly appreciated.
Thanks
James

 

[HERTS P&D]

Start a new thread.

Andy

 

[CBW]

As per Herts P&D (Andy), Start a new thread, this one is over 3 years old. Then once you do post a few photos of setup including where the flue terminates and the condensate arrangement.

 

[Restoration man]

Tayzyboy. Agree with the others start a new thread with your details but just to tell you where we got. We've had the boiler serviced at least twice since this thread and always been told it's fine. Weve never got a conclusion on it. The wife's observation is this never happens in summer only in winter. She recons the cold in winter means the case seals are less flexible and don't work aswell. Can't say it's a daft theory and can't prove otherwise. We've ended up with carbon monoxide alarms in every room and are very wary. We have had several engineers from different companies including the manufacturer and never found anything wrong so other than replacing the whole boiler we've had no option but to live with it.

Cheers