From the flueing question in General Plumbing Forum.

[AWheating]

What boiler is it, and what exactly do you mean by hole not filled in?

Vaillant and Intergas (definitely), and W-B (I'm pretty sure) explicitly state that it's acceptable to core a 125mm hole for a 100mm flue, and use the rubber ring provided to make the external seal, without the requirement to bond to the building fabric with mortar.

150mm hole needed and a flat wall surface for the worcester bosch greenstars and they still require you to seal the hole with expanding foam or sand and cement from the inside.

never seen it advised on a vaillant or intergas but i aint fitted either for a few years tbh.

 

[Chalked]

Re: Outside flue hole not filled in by plumber

Sounds like its been put through the old balanced flue opening and only made up on the inside.

Dont tell anyone but just like mine ( will get it done soon. Honestly)

 

[clarky101]

Re: Outside flue hole not filled in by plumber

Could be four storeys up.....

 

[Phil]

Re: Outside flue hole not filled in by plumber

Lardlord job for plumber? Exposed plastic everywhere with wacking great holes chiseled everywhere?. Contact landlord.

 

[Masood]

Re: Outside flue hole not filled in by plumber

150mm hole needed and a flat wall surface for the worcester bosch greenstars and they still require you to seal the hole with expanding foam or sand and cement from the inside.

You got me thinking there! Just double-checked Vaillant manual and it is definitely 125mm and no mention of sealing. Obviously it's good practice to seal with sand & cement from inside and I always do.

 

[kirkgas]

Re: Outside flue hole not filled in by plumber

Sounds like its been put through the old balanced flue opening and only made up on the inside.

Dont tell anyone but just like mine ( will get it done soon. Honestly)

Haha brilliant, I only sealed round my flue when the builders were coming to build my extension, boiler was about 4 by then, (think I will service it soon)

 

[Ermintrude]

Outside flue hole not filled in by plumber

You got me thinking there! Just double-checked Vaillant manual and it is definitely 125mm and no mention of sealing. Obviously it's good practice to seal with sand & cement from inside and I always do.

Don't all mfrs state that flue must be installed to bs5440? Isn't it explicit that all flues should be sealed against fabric of building and be 25mm from flammable material? Haven't got to hand but from memory?

Can't see any thing in valiant instructions regarding the rubber being ok? The diagrams show all the flue systems touching wall fabric either side. Think it's a bit like their instructions don't state that u can't use speed fit for gas?

 

[SafeGasInstall]

Re: Outside flue hole not filled in by plumber

You got me thinking there! Just double-checked Vaillant manual and it is definitely 125mm and no mention of sealing. Obviously it's good practice to seal with sand & cement from inside and I always do.

Make sure you make good all flues outside with sand and cement

 

[Kev the gas]

Re: Outside flue hole not filled in by plumber

Haha brilliant, I only sealed round my flue when the builders were coming to build my extension, boiler was about 4 by then, (think I will service it soon)

Kirkgas, when your condense bucket is full you can borrow one of mine !!m

 

[kirkgas]

Re: Outside flue hole not filled in by plumber

Don't all mfrs state that flue must be installed to bs5440? Isn't it explicit that all flues should be sealed against fabric of building and be 25mm from flammable material? Haven't got to hand but from memory?

Can't see any thing in valiant instructions regarding the rubber being ok? The diagrams show all the flue systems touching wall fabric either side. Think it's a bit like their instructions don't state that u can't use speed fit for gas?

I'm sure there "were" boilers which did allow the rubber seal to be used as final seal, can't remember which make, it's years since I've done any real work, but there was one we used on a contract which deffo stated that in a high rise install you could up the core size and fit the full flue with rubber tracked through the wall and pull it back to use the rubber as the seal,
Re the MI not stating you can't use speed fit for gas, it's covered under " gas pipeworks must be installed to BS6891"

 

[nickelarsed]

Re: Outside flue hole not filled in by plumber

How to install a flue for a Greenstar boiler - YouTube

Here is what Wooster actually say on it.

 

[hammers4spanner]

Re: Outside flue hole not filled in by plumber

If you plaster the inside and put rubber seal on external what are the actual odds of a poc issue??

 

[Ermintrude]

Re: Outside flue hole not filled in by plumber

Every day is a school day!

 

[kirkgas]

Re: Outside flue hole not filled in by plumber

If you plaster the inside and put rubber seal on external what are the actual odds of a poc issue??

The actual odds are very low, but technically the POC's could enter the cavity and rise up causing a problem above,

 

[hammers4spanner]

Re: Outside flue hole not filled in by plumber

Be interested to know if there is an actual incident where poc's got under the rubber seal and caused an issue .

 

[Ermintrude]

Re: Outside flue hole not filled in by plumber

Be interested to know if there is an actual incident where poc's got under the rubber seal and caused an issue .

Reg man might know?

 

[Masood]

Re: Outside flue hole not filled in by plumber

Don't all mfrs state that flue must be installed to bs5440? Isn't it explicit that all flues should be sealed against fabric of building and be 25mm from flammable material? Haven't got to hand but from memory?

Can't see any thing in valiant instructions regarding the rubber being ok? The diagrams show all the flue systems touching wall fabric either side. Think it's a bit like their instructions don't state that u can't use speed fit for gas?

"If the desired position for the wall penetration is accessible from the outside of the building, you
can drill the hole with a 107 mm diameter core
drill and insert the external wall seal from the
outside of the building.

Push the air/flue pipe (1) together with the external wall
seal through the wall until the external wall seal opens
out again on the outside.
> Pull the air/flue pipe back towards the boiler until the
external wall seal is in contact with the external wall
(¬ fig. 3.6 and ¬ fig. 3.11).
> Make sure that the air/flue pipe (1) is central inside the
hole and that the terminal is correctly positioned with
the inlet grille on the underneath (¬ fig. 3.6 and
¬ fig. 3.11).
> Slide the wall rosette (2) over the air pipe until it is flush
against the wall (¬ fig. 3.7)."

No mention of bonding to building fabric either externally or internally, just the use of rubber seal and rosette. From Vaillant EcoTEC flue installation manual, P.14

http://www.vaillant.co.uk/stepone2/data/downloads/25/44/00/ecoTEC flue instn instructs.pdf

 

[Masood]

Re: Outside flue hole not filled in by plumber

Make sure you make good all flues outside with sand and cement

If you're installing on the 7th or 8th floor (or higher) either you can comply with MIs (as linked above) or you can price yourself out of the job by adding 2 grand for scaffolding. I know what I'd rather do! I go above and beyond MIs by sealing internally with sand & cement anyway.

 

[Ermintrude]

Re: Outside flue hole not filled in by plumber

Flicked through the same . It's amazing what u see when you read!! I only saw

Always thought to fill both sides of the flue with mortar. Fire rated expanding foam to fill voids then 30mm of 4:1
Never done more than a repair above 4th floor! Always binned jobs off because of su ducts. Think there is a fanned flue designed for job though?? I hate flats. Stairs !

What would be in accessible in your mind? 3rd or above? Love lugging the triple 16 rung ladders out, prefer access platform but not always enough money. Now that the flue rubber is on the cards.......

 

[Reg Man]

Re: Outside flue hole not filled in by plumber

Reg man might know?

Don't bait me. Where ever there is a passage for POC to enter the building, there is always a risk. Most of the time nothing will be noticed, its normally when other criteria come in, such as poor terminal position, lack of servicing, when it all goes into danger mode. Look at that incident some years ago, regarding covered passage ways Domonic Rogers died in the upstairs bedroom. Loads of people had the opinion that this could never happen but it did.