Gap in boiler tube help

[Timmy D]

I wouldn’t even worry about it. Looks like the top is nearly touching and due to the angle of flue, the bottom has opened up a bit.

I’m not saying I’d install it like this but if we use a bit of common sense, it’s the air intake. It’s not an air tight seal to begin with, so a 5mm gap, makes very little difference.

It’s not under positive pressure, so any leak in the inner tube won’t get forced out of the air tube but rather sucked in to the boiler and reburnt.

If I found it, rather than break cement, dismantle/reinstall flue, I’d test and likely wrap it with silver tape, refit the clamp and screw the clamp.

I’d also be quite happy to stand up in court and explain my decision process.

Sometimes we as engineers need to use our common sense and on site judgement.

Now if I found something like this......it’s a different story....

 

[solidsponge]

Tbf and afaik, majority if not all boilers or intake/flue arrangements are of a similar setup, as in they have a clamp bracket over a joint, no seals as only air intake.

I wouldn’t even worry about it. Looks like the top is nearly touching and due to the angle of flue, the bottom has opened up a bit.

I’m not saying I’d install it like this but if we use a bit of common sense, it’s the air intake. It’s not an air tight seal to begin with, so a 5mm gap, makes very little difference.

It’s not under positive pressure, so any leak in the inner tube won’t get forced out of the air tube but rather sucked in to the boiler and reburnt.

If I found it, rather than break cement, dismantle/reinstall flue, I’d test and likely wrap it with silver tape, refit the clamp and screw the clamp.

I’d also be quite happy to stand up in court and explain my decision process.

Sometimes we as engineers need to use our common sense and on site judgement.

Now if I found something like this......it’s a different story....

View attachment 81776View attachment 81777View attachment 81778

That looks awful. I'm still not totally happy about it and overall I don't feel its safe, although a gas safe person installed it and a gas safe engineer moved the bracket for me, but he didn't apply any tape and he didn't put any of the self tapping screws in.

Im not sure if I should get someone else out to apply some tape and screw it in or if its not worth it. Even doing that it seems a terrible design to have two pipes the same diameter just meet and then put a cover over it. They could at least overlap, but if this is the design of the boiler and flue then it must be meant to be like this I guess and Ill just always be worried about it.

I also found a video on youtube installing it (slightly different boiler but looks like exact same flue) and he asked the official alpha rep about the holes in the cover and they said they were self tapping screw holes but it does not need the self tapping screws (so why have the holes then!?) Unfortunately in the video he does not show installing the flue part so I cannot see if he had a gap too.

I also turned it on the other day when the heating was on and the water came out at 80 degrees for a brief moment (stated on boiler, apparently not the real temp) and the boiler made a weird clank noise. So it really is not inspiring any confidence from me, even though its brand new (installed by previous owner to just sell house)

 

[solidsponge]

Sorry Im sure no one is interested, but the best photo I can find it appears this is the design flaw imo. I don't see how any engineer can fit it much better, two pipes with the same diameter to meet and that bracket covers the gap, which is inevitable to have a small gap.

(Although I cannot tell from the photo, maybe it does slide in and provide an overlap. One thing I don't have is the plastic covering finishing piece on the wall, that I guess is missing)

The further flaw is, having the "self tapping screw holes" (which according to Alpha tec don't need to be used) means if the bracket is installed slightly forward or back, these holes can let air out by mistake.

 

[Timmy D]

these holes can let air out by mistake.

That’s the thing, it is just an air pipe. It’s fresh air being drawn in.

Not all boilers are “room sealed” with concentric flues, as yours is.

They can be “open flued”, drawing their combustion air from the room, in through the case.

I’m theory, you could completely disconnect the white air pipe, keeping the internal combustion flue connected, and as long as the combustion flue is installed correctly and undamaged, there’s no risk.

It’s not a flaw, it’s a calculated, safety tested design decision.

 

[IND_Nick]

That’s the thing, it is just an air pipe. It’s fresh air being drawn in.

Not all boilers are “room sealed” with concentric flues, as yours is.

They can be “open flued”, drawing their combustion air from the room, in through the case.

I’m theory, you could completely disconnect the white air pipe, keeping the internal combustion flue connected, and as long as the combustion flue is installed correctly and undamaged, there’s no risk.

It’s not a flaw, it’s a calculated, safety tested design decision.

To be fair, it's not just an air pipe. It's an integral part of a room sealed, balanced appliance that should be installed correctly. I appreciate what you are saying, and with experience you can make, correctly, decisions on safety. However, as a rule there should not be holes or gaps of any sort in this type of flue.
Open flue/naturally vented appliances are completely different and in my opinion should not be mixed up in this thread as completely different.
The original query was the gap/hole in the flue. If the collar had been installed correctly covering the joint equally, tightened etc, job done.

 

[solidsponge]

Thank you for your information guys. On the one hand it appears fine, a gas safe engineer originally installed it (previous owner) I've had another engineer say its ok and move the bracket (he also said it wasn't a fan of the boiler though) On the other hand it doesn't feel safe to me to have a gap in a pipe like this.

Here is a picture of the outside, you can see the white showing through and also that is the side where there is a gap on the interior, so I guess it's at a slight angle probably.

The boiler has good reviews online but I don't feel that safe with it, it seems to make a clank inside when the heating is on for a while and you turn on the hot water in the kitchen next to it, the temperate shoots up in temperature briefly and Ive twice now heard a clank noise inside.