Boiler flue issues - basement and flue termination

[Mjward]

Hello

new to the forum so will say thank you in advance to all and any assistance you can provide.

background: current boiler installed in Basement in 2011. Six months ago it failed gas safety for the first time, I sought a second opinion and same thing. Diagnosis being that the flue termination is too close to the ground.

Nothing has changed re the setup so I’m not going to get bogged down in why it was fine and now it isn’t,the regs are the regs.

after a bit of googling I’m confused about the rules that govern this, in particular definitions of the terminology. I know flue clearance must be 300mm from the ground but clearance of what? My logic would have thought the outlet of the flue ie where the gases escape (which is 2.5m from ground) but can only assume my setup is failing because it covers the height the piping exits the property at the horizontal (at 0.15m above a dug out area that enables circulation for an airbrick into the basement)

if it is in fact 300m from where the pipe simply exits the property (even if not terminated there) what are my options?

1) does increase the depth of the dug out area to increase the distance from it to the horizontal to 300mm suffice (even if still below adjacent “normal” ground level)
2) drill through room above and take flue further vertical so it doesn’t exit the property horizontally until 300mm above normal ground level
3) anything else?

once again appreciate any advice you can give
Thanks

 

[PETE 123]

If the air intake for boiler is below the grd then it would fail as if it snowed may block up air intake or effect boiler operation.

 

[Mjward]

Hi PETE 123

Thanks for your response. It was my understanding that the air intake is only happening at the top of the flue vertical extension kit (in red in the diagram) which is 2.5m above ground. The pipework that is coming out from the boiler in the basement and exiting the property below ground is not open to air intake, it's just a bend upwards to the extension

 

[gmartine]

At least 300mm of clearance above ground level (I). At that height though (< 2m) you'll have to install a terminal guard, no need to raise it to 2.5m.

 

[Mjward]

At least 300mm of clearance above ground level (I). At that height though (< 2m) you'll have to install a terminal guard, no need to raise it to 2.5m.

So can you understand why two gas Safe engineers have failed the setup I have given the outlet for the flue on top of flue extension is 2.5m above ground level. They seem to be solely judging it on height pipework exits the property which is not 300mm above ground but surely the regulations deal with the termination of the flue ie where the gases are escaping and don't care about covered pipework itself?

 

[Last Plumber]

As @PETE 123 points out, if the air intake was in a dug out below ground level, it would fail.
Is the air intake in there?

Have you a photo of the external flue and dug out.

It is possible that there has been a misunderstanding of the regs but we would need to see the actual flue and its surroundings in order to pass comment.

 

[Mjward]

As @PETE 123 points out, if the air intake was in a dug out below ground level, it would fail.
Is the air intake in there?

Have you a photo of the external flue and dug out.

It is possible that there has been a misunderstanding of the regs but we would need to see the actual flue and its surroundings in order to pass comment.

Apologies I'm not currently at the property so don't have access to better pictures but pls find these from my records include a diagram of it helps

[automerge]1583318119[/automerge]
Plus image from valiant themselves of the extension

 

[ShaunCorbs]

I would want the flue to the same height as the plume kit eg replace the flue and bring it full height both the air and exhaust

 

[Mjward]

I would want the flue to the same height as the plume kit eg replace the flue and bring it full height both the air and exhaust

Hi Shaun

Thanks for helping. Not sure I fully understand your suggestion, what's the difference to a flue and plume kit? (Apologies for my ignorance!)

 

[ShaunCorbs]

Hi Shaun

Thanks for helping. Not sure I fully understand your suggestion, what's the difference to a flue and plume kit? (Apologies for my ignorance!)

plume kit is what you have now the flue is moving the air intake from below ground to where the existing plumb kit is (top)

 

[Mjward]

plume kit is what you have now the flue is moving the air intake from below ground to where the existing plumb kit is (top)

Do you have an example of the kit I should change it with? I'm still not sure I understand what my current setup is doing wrong

 

[ShaunCorbs]

Do you have an example of the kit I should change it with? I'm still not sure I understand what my current setup is doing wrong

your air intake is below the ground so could get blocked / submerged

and best ask a gas safe engy to sort it out

 

[Last Plumber]

Hi Shaun

Thanks for helping. Not sure I fully understand your suggestion, what's the difference to a flue and plume kit? (Apologies for my ignorance!)

Hello.
The flue on your boiler has two pipes. One external (large 4" white metal) which draws air into the Boiler combustion chamber to mix with the fuel to create the right mixture and an internal (2" plastic) exhaust pipe which takes away the products of combustion.
In your case the flu pipe exits the building into the dug out and the air intake terminates there. The exhaust is then extended away from the ground, window and dug out to a satisfactory position. However, it is possible for your air intake could become blocked with snow/leaves etc or if the dug out fills with water, that could enter the air intake and ultimately the boiler. Even if you covered it with a mesh guard to stop things falling in, it could still become blocked by things lying over it like the board you have there now.

If the air intake becomes blocked or partially blocked, then the Boiler will not be supplied with enough oxygen to burn safely/correctly. This is why it falls foul of the rules and regulations. It should never have been installed like that really, so it was never fine.

You need to get a gas safe registered person to make the necessary alterations and make it safe.

 

[gmartine]

So can you understand why two gas Safe engineers have failed the setup I have given the outlet for the flue on top of flue extension is 2.5m above ground level. They seem to be solely judging it on height pipework exits the property which is not 300mm above ground but surely the regulations deal with the termination of the flue ie where the gases are escaping and don't care about covered pipework itself?

Yes, I can now...

A "plume kit" or as Vaillant describe a "vertical termination kit" has been used to raise the flue intake from it's termination point to 2.5m (it is not a flue extension) however the flue exhaust still terminates below ground level which is why it has been pulled up. As described above a balanced flue attached to your boiler contains both the intake and exhaust ports, the plume kit will need to be replaced with an actual flue that can terminate at 300+mm above ground level as long as it is caged or above 2m where it does not.

You can see from the diagram that the vertical termination kit is a lesser diameter from the actual flue exiting the boiler, that's because it is only extending the exhaust port meaning in your case the intake (at termination point) will still be below ground level with the potential to get blocked.

Your confusion (and mine a bit) lies in the belief the plume kit is the same as an actual flue and therefore terminates at a legal height, it does not it only partially does via a plume (exhaust) extension kit. Hope that clarifies things.
[automerge]1583411327[/automerge]

Yes, I can now...

A "plume kit" or as Vaillant describe a "vertical termination kit" has been used to raise the flue exhaust from it's termination point to 2.5m (it is not a flue extension) however the flue intake still terminates below ground level which is why it has been pulled up. As described above a balanced flue attached to your boiler contains both the intake and exhaust ports, the plume kit will need to be replaced with an actual flue that can terminate at 300+mm above ground level as long as it is caged or above 2m where it does not.

Corrected, sorry way around.
[automerge]1583411399[/automerge]

Yes, I can now...

A "plume kit" or as Vaillant describe a "vertical termination kit" has been used to raise the flue intake from it's termination point to 2.5m (it is not a flue extension) however the flue exhaust still terminates below ground level which is why it has been pulled up. As described above a balanced flue attached to your boiler contains both the intake and exhaust ports, the plume kit will need to be replaced with an actual flue that can terminate at 300+mm above ground level as long as it is caged or above 2m where it does not.

You can see from the diagram that the vertical termination kit is a lesser diameter from the actual flue exiting the boiler, that's because it is only extending the exhaust port meaning in your case the intake (at termination point) will still be below ground level with the potential to get blocked.

Your confusion (and mine a bit) lies in the belief the plume kit is the same as an actual flue and therefore terminates at a legal height, it does not it only partially does via a plume (exhaust) extension kit. Hope that clarifies things.
[automerge]1583411327[/automerge]


Corrected, sorry wrong way around.

 

[Mjward]

Fantastic. Thank you...I've gone from completely baffled to 100pct understanding the situation now.

I think cheapest solution is to take the flue vertically up into the room above and then horizontally out which would be greater than 300mm.

Much appreciated

 

[gmartine]

I don't think they're will be a great deal in it tbh as the new termination point will need to be core drilled again. Get a couple or three quotes and see what the engineers recommend as it looks like you have a couple of windows in close vicinity.

 

[Mjward]

I don't think they're will be a great deal in it tbh as the new termination point will need to be core drilled again. Get a couple or three quotes and see what the engineers recommend.

I've got a plumber I've had good success with recently who estimated it as £250-350 which seems reasonable

 

[AlsPlumbing]

Well, I've just come across this thread for the same reason. I too need to fit a new boiler in the basement and find a means of a good termination of the flue.
My plan was to do exactly as Mjward suggested in his original drawing. Which only shows a Flue and doesn't go into detail of the air intake. - which is fine. ( no talk of plume kits)
If it is terminated above ground ( at the correct height) then the only draw back I can see is Ingress of rain, snow or leaves which would gather in the ' cut out' opening or pit which allows the flue to exit the basement in the first place.
So, my plan would be was to build a small structure around this with pitched roof. build a couple of doors on the front and then this would give access to inspect any joints on the outside of the property and of course would keep it weather tight.

please let me know your thoughts.

 

[king of pipes]

No no no ! You can't do that must be open all sides it can have a wire mesh guard fitted around the air intake . Kop

 

[gmartine]

Any chance of running the flue internally, check your boilers MI's as you should be able to run the flue quite a distance horizontally before turning upwards.

 

[AlsPlumbing]

Any chance of running the flue internally, check your boilers MI's as you should be able to run the flue quite a distance horizontally before turning upwards.

Unfortunately not. My customer said his kitchen cupboards will sit over this spot.
[automerge]1588411004[/automerge]

No no no ! You can't do that must be open all sides it can have a wire mesh guard fitted around the air intake . Kop

Cheers for reply.
Yes, I know this, but the terminal will be outside. It would be off a vertical flue with pitched flashing coming out from the 'cupboard pitched roof' only problem i think would have is the external wall distance, which i'm going to look up now. Anything more than 300mm, I'm probably stuffed!