Trainee gas questions in this thread ONLY please

[Dotty]

Thread from open forum merged in. Sorry Lee, it's bumped your post down!

 

[bassmonster]

Unsafe situation? It only has a rubber seal on the outside but not cemented inside.....

 

[kirkgas]

Depends on MI of specific boiler, some allow rubber collar to be used as weather seal, only required on the outside to stop POC's re entering property and going up cavity, inside seal is only for decor

 

[bassmonster]

Thank you Kirk. I'll have a nosey in the MI to be sure

 

[albatross]

Unsafe situation? It only has a rubber seal on the outside but not cemented inside.....

View attachment 17879

View attachment 17880

If neither wall is cemented its at risk. Flue must be sealed to the building with cement.(not expanding foam/silicone. Also flue must be adequately supported and the rubber will not do that and just being attached at the boiler is not good enough. If it was low enough some flues could work loose/ be pulled out causing fumes to go into the room if not securely cemented in.

 

[Killy Bing]

If neither wall is cemented its at risk. Flue must be sealed to the building with cement.(not expanding foam/silicone. Also flue must be adequately supported and the rubber will not do that and just being attached at the boiler is not good enough. If it was low enough some flues could work loose/ be pulled out causing fumes to go into the room if not securely cemented in.

reminds me, i have a flue i need to go fit....
damnit

 

[tamz]

If neither wall is cemented its at risk. Flue must be sealed to the building with cement.(not expanding foam/silicone. Also flue must be adequately supported and the rubber will not do that and just being attached at the boiler is not good enough. If it was low enough some flues could work loose/ be pulled out causing fumes to go into the room if not securely cemented in.

Depends on the manu. Worcester and vaillant don't care much but baxi and vokera want it sealed.
Common sens says mix up some compo but common sense also says i've more chance of having a heart attack humping Kylie than anyone ever being at risk of anything.

 

[kirkgas]

Albatross, EVERY un cemented flue isn't AR, you need to be boiler specific when you say that as some manufacturers allow the rubber seal, in fact (can't remember make model) I remember we fitted some boilers in 5 high flats and chose the boiler as we could fit the flue and rubber seal from the inside, I'm sure we had to drill 6" hole rather than 5" to accommodate rubber ring going through from inside, I've always done what manufacturer said, but on contracts where we had builders on site anyway I always got them to cement the flue holes, but I wasn't paying for a 5 high scaffold to seal them when I could choose a different boiler and fit flue from inside, the wall on the inside is only for decor, if the flue corrodes the POC's would go up the cavity, and any fumes blowing back in from outside would always go up the cavity rather than right back into the house

 

[albatross]

Albatross, EVERY un cemented flue isn't AR, you need to be boiler specific when you say that as some manufacturers allow the rubber seal, in fact (can't remember make model) I remember we fitted some boilers in 5 high flats and chose the boiler as we could fit the flue and rubber seal from the inside, I'm sure we had to drill 6" hole rather than 5" to accommodate rubber ring going through from inside, I've always done what manufacturer said, but on contracts where we had builders on site anyway I always got them to cement the flue holes, but I wasn't paying for a 5 high scaffold to seal them when I could choose a different boiler and fit flue from inside, the wall on the inside is only for decor, if the flue corrodes the POC's would go up the cavity, and any fumes blowing back in from outside would always go up the cavity rather than right back into the house

It is. Gas Regs say a flue must be supported and there must not be an opening in the building within 300mm.

You can do what you just said as long as you cement the inside course and just have the rubber outside. Then you have supported the flue and sealed it. I have done it too.

 

[Mike Jackson]

Gas Regs don't. Building regs do but MIs supersede building regs.

 

[tamz]

This one has been done to death in neumerous posts.

 

[kirkgas]

It is. Gas Regs say a flue must be supported and there must not be an opening in the building within 300mm.

You can do what you just said as long as you cement the inside course and just have the rubber outside. Then you have supported the flue and sealed it. I have done it too.

So are you agreeing or disagreeing with me?
First you said I'm wrong then you said you did the same, if the outside hole isn't cemented is it AR? I said no and you said it was

 

[bassmonster]

Here's another Flue photo. The hole above is for an extractor fan which isn't working. Am I right is classifying the pipe as ncs as it's too close to the flue? Also the hole above, ncs or AR?

 

[albatross]

So are you agreeing or disagreeing with me?
First you said I'm wrong then you said you did the same, if the outside hole isn't cemented is it AR? I said no and you said it was

I'm saying It's ok to do and I've done it as long as you cement one side, either inside or out, it doesn't matter which.

Best practice is cement both inside and out.

High level jobs cement the inside. It will support and hold the flue, comply with not allowing an opening within 300mm of a terminal and stop draughts. Leaving gaps won't help with gas bills.

Then you can sleep at night knowing no one can question your work/call you back. In our job it's not worth sitting in a grey area, cover your backside for an easier life. I'm here to give good advice, not argue and fall out. Even if something is not written down in law or MI's it's worth erring on the side of safety and doing little things like mixing a bit of cement.

 

[mutley racers]

[DLMURL]http://www.radmidlands.co.uk/Downloads/ControlsDom.pdf[/DLMURL]

page 6

https://docs.google.com/file/d/0B6zTTicYyEudZnhHUVlSRnI5cVk/edit

another good source of info for guys learning the trade.

Can't seem to open that bottom one

 

[Whyme]

Here's another Flue photo. The hole above is for an extractor fan which isn't working. Am I right is classifying the pipe as ncs as it's too close to the flue? Also the hole above, ncs or AR?

the flue touching the downpipe is ncs, the outer isnt going to get hot enough to bother it. just guessing on what the measurements are from the pic the extractor hole does need bricking up or sealing somehow (since it isnt used anyway). then uve just got an ncs good times..

 

[Ermintrude]

AR. Easy . Old vent needs to be closed outside as flue gases can fill cavity .

 

[PlumbersMate]

Write ups question.
Do you have to show all your results ie when you calculate a purge write it all in write up, or just say calculated purge and then carried out? Likewise for CPA and burner pressures etc
thanks

 

[Killy Bing]

Write ups question.
Do you have to show all your results ie when you calculate a purge write it all in write up, or just say calculated purge and then carried out? Likewise for CPA and burner pressures etc
thanks

if you're doing purging keep all your working out.
if the purge fails you need to look back through your working out.
along with it covering your backside and making the next time easier.

 

[Ermintrude]

Or set up a purge stack and burn off 20m3

 

[bassmonster]

Write ups question.
Do you have to show all your results ie when you calculate a purge write it all in write up, or just say calculated purge and then carried out? Likewise for CPA and burner pressures etc
thanks

I am writing up all my calculations. Your course center will give you a form stating pipe and meter volumes etc to fill in.

 

[Killy Bing]

Or set up a purge stack and burn off 20m3

isn't that a flare stack

 

[Ermintrude]

Flare / purge it's just a bit of garden hose and a 15mm with a 22mm reducer with some holes drilled in it stood next to an sf2 on low flame .... On the lead roof of that church

 

[bassmonster]

what's a purge stack?

 

[Killy Bing]

what's a purge stack?

with commercial volumes of gas you cant just cut a pipe.
you have to purge it from one end of the line with a blower for air or with nitrogen.
at the other end you have a purge point which you connect your hoses to run to your purge or flair stack.

stacks are basically a unit with a gauge to set your flow rate and then a pipe off the top to disperse the gas safely to open air.

that's pretty basic explanation