fanned flue installation query

[oldplumber]

Went to service an ideal boiler yesturday and noticed flue wasnt secured in cavity wall other than by pushing internal and external rubber covers upto walls. this meant that the flue wasnt held at an angle to drain condensate back into boiler, and it was not actually secure.

rang gas safe to query this and told what do you feel?, so i said it was definitley ncs if not ar. he responeded well fix it in on external wall and alls ok! if customers complain we will investigate but otherwise its ok. This was on a newbuild estate of 40 plus houses. I always seal and make good flues on the outside wall, not so worried internally, just wondered what the rest of you do/think😕

 

[kirkgas]

it depends on the manufacture of the boiler and the size of the hole, some MI's allow the rubber seal as the way to seal the hole, as long as the hole isnt too big allowing the flue to possibly move ab out and break the seal at the boiler (AR) some MI's tell you to make good the hole therefore it must be AR if not sealed, dont see how it could ever be NCS as the flue is too close to an opening in a building

 

[wnjswozo]

on some condensing boilers the flue can be run level,ie does,nt need 3 degree fall ,as internal flue of the flue has the fall,worcester,s for one,as for sealing it should be sealed get your foam gun out

 

[oldplumber]

gas safe technical adviced it was ncs, ar was not needed, not what i would have thought tho,

Noted about flues having internal falls, but the neighbours flue actually drained outwards (until i shoved it skyward for them)

The old foam gun did come out of the van, still that leaves 39 plus flues to be sorted.

 

[Billy Bob Bob]

yes but what about maintenance when the expansion vessel fails? that flue will need to come out (if its behind boiler)

 

[wnjswozo]

leave it in add another external pressure vessal

 

[REDSAW]

leave it in add another external pressure vessal

yup, thats what we do.😎

 

[oldplumber]

yes but what about maintenance when the expansion vessel fails? that flue will need to come out (if its behind boiler)

you do wot i do, install remehas and the expansion vessel comes out the front of the boiler, B*gger all this taking them off the wall to replace an expansion vessel. If you cant do that whip off the flue elbow and out comes the expansion vessel, or you can go back to the hard way and drop the boiler off the wall. Better than having fumes in your cavity coming back intio your house and headaches all round

 

[Billy Bob Bob]

leave it in add another external pressure vessal

i do this were possible,but some people dont want a external vessel were possible i try to duct the wall on new installations,old plumbers statement to use filler foam is flawed 1,you have to use heat res foam for flues or intumesant foam 2, the flue will never come out again at least if the holes been cored you can use sand and cement which you have more chance of breaking after should the flue need removing

 

[oldplumber]

I always use intumescent foam but i dont see that this is really needed as the flue already has an airgap where the air intake is surrounding it, and a hacksaw blade will cut through foam a lot quicker than sand and cement which would have to be chiselled out. My norm is to use a bit of foam to secure the flue and render the exterior with sand/cement for the remainng inch to give a water resistant finish.

 

[tamz]

I always use intumescent foam

Well why did you not use some on the service job you were at if it bothered you?
Would have been quicker and cheaper than phoning gas safe 🙂

 

[oldplumber]

Well why did you not use some on the service job you were at if it bothered you?
Would have been quicker and cheaper than phoning gas safe 🙂

Why not read the threads first, i did seal it and the phone call was free anyhow, always use the customers line, my query was, should it have been permanently sealed in in the first place? your views required please. Since you dont have an opinion your response was rather puerile to say the least.😡

 

[tamz]

puerile

Fancy word for a saturday afternoon. I may be a puella?

my query was, should it have been permanently sealed in in the first place?

In answer to your question, read the MI's. Not all require this.
All manu's allow fitting from inside where external access is impossible eg flats, so no external seal other than collar there.
If you were being pedantic you could say the poc's may find their way into the cavity and exit anywhere in the building!

As long as it had both collars fitted correctly then at worst NCS
No collars AR
Sometimes all that is required is common sense.

As for using expanding foam to fill around the flue, in my opinion this should not be done for previous mentioned reasons.
You personally may never have to remove a flue but someone may have to and i can guarantee it takes more than going around it with a hacksaw blade. Try it sometime.