Gas pipe sizing

[cyclonebri2]

Hi, can anyone help difuse a potential problem with our contracter/plumber?

As basically as possible we are renovating a fairly good sized house. The builders ripped out an existing 28mm gas main that ran 8 metrs through the property.

It supplied a 100btu CHB and tee'd off to feed a 5kw gas fire and an unknown load for a kitchen gas hob.

So, the plumber has relaid a 22mm main that now has to supply a 35/38kw boiler and the 5kw gas fire. The gas feed to the hob is no longer required, but there will be a take off a metre or so along the run for a 2nd gas fire.

Hope thats clear. Is the 22mm pipe good enough for this load????

Need to acy quickly before the whole lot gets boxed and plastered,

Cheers.

 

[kevplumb]

As basically as possible we are renovating a fairly good sized house. The builders ripped out an existing 28mm gas main that ran 8 metrs through the property.

why ??

Hope thats clear. Is the 22mm pipe good enough for this load????

no chance it's not big enough for the boiler by the sound of it

Need to acy quickly before the whole lot gets boxed and plastered,

act then sack the numpty

 

[cyclonebri2]

The pipe was removed as it was in a suspended ceiling under a soild concrete floor and got damaged, but would have had to have been raised anyway.

Sacking the numpty, no, we are reasonable folks, as is the builder, we would like to keep this friendly but rule out any errors, sure you know what I mean?

From my own experience the reduction in pipe size seems "unwise", just need something concrete either way before we adress the issue

 

[davebgas]

I would have hoped the fitter calculated the correct pipe size for the installation. Ask them to demonstrate this calculation. It's bread and butter for a proper engineer. Ask them how they intend to keep a max 1mb drop across the system with that size pipe and appliances.

 

[kevindgas]

I would have hoped the fitter calculated the correct pipe size for the installation. Ask them to demonstrate this calculation. It's bread and butter for a proper engineer. Ask them how they intend to keep a max 1mb drop across the system with that size pipe and appliances.

sound advice there dave agree 100%

 

[cyclonebri2]

So, can anyone do their own calculation anmd determine if correct or not???

Dave, don't know if your signature is right or what re Canada, but here in the UK plummers are not described that way

Maybe if you are so equipted and based on the info I have supplied you could make a call???

 

[bengasman]

Sacking the numpty, no, we are reasonable folks, as is the builder, we would like to keep this friendly but rule out any errors, sure you know what I mean?

You may want to keep this friendly, but some one who is clearly incompetent, or simply does not care how things should be done, should be sacked. It is not an error, it is a bad case of flawed practice.

 

[bengasman]

So, can anyone do their own calculation anmd determine if correct or not???

Apart from insufficient data without which the calculation can not be done, we do not give safety critical information on an open forum. You can carry on with the current chap, and afterwards ask for an inspection from by an impartial inspector. The downside of that of course is that he will turn the gas off if it is not up to spec.

 

[davebgas]

I can't give you a calculation because you have not given ALL required information
how many elbows, tees, reducers, etc etc etc.
Yes I am in the uk and my signature is correct. Anyone can do the calculation yes but I feel your supposed 'plummer' (which should be 'plumber') should be doing this. If he can't then either
a) he's not gas qualified and a danger
b) incompetent

as has already been said that size boiler with 2 fires will not operate on 22mm under full load. Does this person not even suspect that's the case?? 28mm supplying a smaller boiler but somehow 22mm will??

You're paying the man not me, we won't do his job for him by sizing up your gas carcass.

 

[bengasman]

I can't come up with any 38 kW combi, what make and model is it? Maybe it is a lot smaller than 38 kW.

 

[doitall]

Yep quick calculation says minimum 28mm.

That's on 48Kw at 8m, so could even need to be 35mm.

Best to get an RGI to do the job.

 

[cyclonebri2]

It is not an error, it is a bad case of flawed practice.

It's more probably a case that the builder did not explain the need for the existing gas fire supply to the plumber, as they had removed this also when demolishing the roof.

I dodn't think it's incompetant, just bad communication. As said the builder has a load more work to do so I need to be on frim ground before I raise the issue,
Cheers

 

[cyclonebri2]

You're paying the man not me, we won't do his job for him by sizing up your gas carcass.

All I was asking is am I correct in thinking an error has been made, I'll give a bit more detail

 

[cyclonebri2]

Yep quick calculation says minimum 28mm.

That's on 48Kw at 8m, so could even need to be 35mm.

Best to get an RGI to do the job.

Thanks for that, he he a corgi reg guy, methinks the builder has not given him the full SP

 

[cyclonebri2]

I can't give you a calculation because you have not given ALL required information
how many elbows, tees, reducers, etc etc etc.

Ok, the pipe from the meter is 28mm for about 1ft vertically, 90 deg elbow then is reduced (now) to 22mm. It then runs straight for about 8mtr before sweeping, (bend), down a mtr or so then through a couple of elbows into the boiler.

the 1st gas fire which is non existant at present will eventually be fed from the short 28mm section as it is very close to meter. The feed to the 5kw fire that they have missed originally came from a tee at the end of the straight run where they now have a bend. There is then a 15mm feed of about 11mtrs and 5 elbows to the fire.

The boiler is a 25kw unit which theoretically is just sufficient to heat the house. We fully expect to have to change this in the future to something like a 35kw unit. The builder was made aware of this.

Yes of course I can challenge him, (the plummer), to prove the sizing, but we are dealing through the builder and if it's his error, if indeed there is an error, I would like to be armed with something substantial

Anyway, regardless, thanks for taking the trouble to reply.