How far out of horizontal can a flue be?

[woodface]

How far out of horizontal can a flue be?

Our new combi boiler install (gas safe registered engineer, contracted by national firm) has its flue pointing 5 degrees up from horizontal. Presumably increasing the risk of condensed vapour dripping back toward the boiler.

This also means the outer collar does not sit flat to the wall, leaving small gaps. For rain or gases.

The inner collar has been cut leaving a one inch gap! (I imagine he couldn't get it to fit flat).


Building regs apparently say:

1) A boiler flue must be appropriately fixed in place and sealed on either side of the wall to ensure the emissions cannot return into the property via any gaps around the flue itself.

(No collar seal means it fails on this point?)

2) There are regulations in relation to the angle at which the flue is installed to protect from any water or chemical droplets formed within the pipe from dripping back into the boiler.

I can't find the full wording to see if a specific angle is mentioned.

Before I contact the firm who assigned him this job, I 'd like to know if you agree that the hole needs to be remade level.

 

[DP]

Before you jump to conclusion, check the manual as to slop of flue
Flue sealed on the inside, so how are the fumes going to enter the room where the boiler is fitted?

2) There are regulations in relation to the angle at which the flue is installed to protect from any water or chemical droplets formed within the pipe from dripping back into the boiler.

Where did you get this nugget from?

1) A boiler flue must be appropriately fixed in place and sealed on either side of the wall to ensure the emissions cannot return into the property via any gaps around the flue itself.

GSIU is the document that covers gas work. Manufacturers manual has the final say regarding appliance in question

 

[DP]

The inner collar has been cut leaving a one inch gap! (I imagine he couldn't get it to fit flat).

You are imagining wrong, naughty of the chap but you are assuming too much. Have seen this collar not even fitted at times

This also means the outer collar does not sit flat to the wall, leaving small gaps. For rain or gases.

Post a picture of that collar please

Our new combi boiler install (gas safe registered engineer, contracted by national firm) has its flue pointing 5 degrees up from horizontal. Presumably increasing the risk of condensed vapour dripping back toward the boiler.

I would be quite happy with that to happen if the manual says so

 

[mcmoby69]

You can ask gassafe to inspect the install if you have concerns.
Does look a tad iffy to me.

 

[Madrab]

Certain boiler manufacturers ask for a flue fall back to ensure that the flue condensate does run back to the boiler. Others have the fall back built into the standard flue, so the flue is then fitted horizontally.
InterGas MI -
The horizontal wall terminal must be installed level as the flue terminal already has a 3 degree rise built in. If the use of flue extensions are needed then they must be fitted with a 3 degree fall back to the boiler and have a bracket fitted ever meter to support the flue
Vokera MI -
The flue system should have a minimum of 1º; maximum of 3º rise from the boiler to outside, to ensure any condense fluid that forms, is allowed to drain back to the appliance.

As long as the annular space between the flue and the wall is sealed with a suitable medium (e.g. mortar) then that's ok. To meet the regs a flue should be sealed internally and externally but the internal wall collar isn't too important. Looks like he forgot to put it around the flue when fitting so has cut it and then fitted it, seen it many times, he could have been neater about it though TBH.

 

[woodface]

Thanks everyone. I tracked down a Viessmann flue MI which says ≥3 degree fall (50mm per metre) toward the boiler, so it sounds okay. I think building the fall into the flue is much neater - I'd never seen a slope like this before.

 

[vulcancontinental]

He cut the collar because he forgot to put it on and couldn't be bothered the disassemble it I reckon.