Gas pipe sizing question

[Bodgitnscarper]

I needed a boiler fitting before Xmas so was pleased that a local firm was able to do it. The guy who came round seemed very knowledgeable but then he didn’t fit it-he sent 2 young lads. They ran the pipe from the back of the external meter box into the extension in 28mm pipe, which in the clips, sticks out about 45mm, up the wall and along the underside of the 1st floor joists. After approx 3m it tees off to 2x 22mm, a further 2m to the boiler with 1 more 90 bend. The other branch of the tee is for a possible future high efficiency gas fire. This 22mm has been capped off and left under the floor into the main house.
The gas flow rate for the boiler (WB 28cdi classic) is 4.2m3 The gas flow rate for the proposed fire is 1.0m3. My interpretation of the sizing charts is that 22mm would have been adequate for the incoming all the way to the boiler and then 15mm to the fire. Instead I have this ridiculously large pipe up the wall and under my ceiling that, if run in 22mm would have fitted behind my dot & dab and also through the joists rather than under them. Is there a reason for the 28mm and is there a way to hide it?
I also note that where the pipe goes into the house (although the hole isn’t filled yet) there is no sleeving where it goes through the rim joist or the part that will be in the wall.
Any comment or advice will be appreciated. Thanks.

 

[DP]

Gas pipes cannot be encased unless cavity is ventillated. So behind dot and dab it is no no.

Re gas pipe in 28, I am with the fitter as gas pipe sizing is easy for some, others make a pigs ear of it.

 

[Bodgitnscarper]

Thanks DP. What are the regs re pipes under floorboards then? The original pipe went under my lads bedroom before we moved the meter.
I take it therefore that it cannot be hidden in a stud wall either?

 

[durhamplumber]

5metre run to a 28kw boiler..with tee to fire.That seems well within limits for 22mm pipe.

 

[FiremanT]

Gas pipes cannot be encased unless cavity is ventillated. So behind dot and dab it is no no.

New builds do it all the time, even to the extent of dropping a gas pipe for the fire in the middle of the wall. Exactly where I always wanted to fit my surround brackets

I have always understood that it is made permissible by encasing the protected pipes in dot n dab adhesive. I am sure that I have read guidance to that effect.

 

[John D v2.0]

encasing the protected pipes in dot n dab adhesive.

Probably more likely that the plasterboard fitters are not gas qualified so they have no idea whether it's allowed. It's then down to the person commissioning the fire to deal with.
Or maybe plasterboard has enough natural ventilation behind anyway though, certainly does through the vertical joints of a blockwork wall.

 

[FiremanT]

Probably more likely that the plasterboard fitters are not gas qualified so they have no idea whether it's allowed. It's then down to the person commissioning the fire to deal with.
Or maybe plasterboard has enough natural ventilation behind anyway though, certainly does through the vertical joints of a blockwork wall.

No

 

[Razor900]

Probably more likely that the plasterboard fitters are not gas qualified so they have no idea whether it's allowed. It's then down to the person commissioning the fire to deal with.
Or maybe plasterboard has enough natural ventilation behind anyway though, certainly does through the vertical joints of a blockwork wall.

Was that an ironic post??

Just asking as you're also not qualified either

@FiremanT is quite correct the gas pipe can run behind the plasterboard as long as there's a continuous run of adhesive either side

I can't imagine a 28kW boiler eats 4.2 m3 of gas per hour

 

[oilboffin]

I wondered about that too razor.Bob

 

[Dan Robinson]

the gas pipe can run behind the plasterboard as long as there's a continuous run of adhesive either side

Thus rendering it not a void or duct.

 

[Razor900]

Thus rendering it not a void or duct.

You made it too easy for him Dan

 

[DP]

The gas flow rate for the boiler (WB 28cdi classic) is 4.2m3

Which number is correct- boiler model or the gas consumption ( in which case will not be 28kw)

 

[John D v2.0]

@FiremanT is quite correct the gas pipe can run behind the plasterboard as long as there's a continuous run of adhesive either side

I hardly call that "encased", but as I say it is down to the person commissioning the fire to decide not the person who isn't qualified

 

[Razor900]

I hardly call that "encased", but as I say it is down to the person commissioning the fire to decide not the person who isn't qualified

But it doesn't matter what you call it John with all due respect you aren't competent to advise the OP are you?

 

[dilalio]

Thus rendering it not a void or duct.

Duh! It’s not rendered, it’s d&d’d adhesive