Gas pipe reduction query

[Spenbeck]

I’ve just had a new Ideal35 boiler fitted and was told that my existing 15mm gas pipe was incompatible and I would need to have it replaced with 22mm piping. This involved a new pipe run of approx. 10m. When installation was complete I noticed that the gas engineer had simply attached the new 22mm pipe to the old 15mm pipe approx .5m outside the meter box.
I mentioned to him that if this was a water flow that I was wanting to increase then his setup would not work, you can’t go from a small pipe to a large pipe and expect to get better flow. His reply was that gas is different, “it’s all about volume not flow”.
Can anyone tell me if this is correct as I’m still dubious.
many thanks

 

[Brambles]

Assuming that the boiler you have had fitted is an Ideal Logic 35 Combi - that requires a gas supply to support 35.4kw net.

From what you describe the gas pipework installed is significantly undersized. Using 15mm before upsizing to a larger diameter is fine, but it restricts the overall length of pipework that can follow.

The regulations require a pressure drop if no more than 1mb from the meter to the appliance.

From the pipework you have described, I would gues that the pressure drop is in excess of 1.5mb.

Assuming that you have no bends, reducers or tees ( which you will have) from the meter to the appliance 0.5m of 15mm followed by 10m of 22mm alone will give a pressure drop of 1.3mb.

The appropriate regulation is the Gas Safety (Installation and Use) regulations 18 to 24 part D.

A definitive calculation can be completed if you post a sketch of the actual pipe layout.

Hope this helps

 

[Spenbeck]

Assuming that the boiler you have had fitted is an Ideal Logic 35 Combi - that requires a gas supply to support 35.4kw net.

From what you describe the gas pipework installed is significantly undersized. Using 15mm before upsizing to a larger diameter is fine, but it restricts the overall length of pipework that can follow.

The regulations require a pressure drop if no more than 1mb from the meter to the appliance.

From the pipework you have described, I would gues that the pressure drop is in excess of 1.5mb.

Assuming that you have no bends, reducers or tees ( which you will have) from the meter to the appliance 0.5m of 15mm followed by 10m of 22mm alone will give a pressure drop of 1.3mb.

The appropriate regulation is the Gas Safety (Installation and Use) regulations 18 to 24 part D.

A definitive calculation can be completed if you post a sketch of the actual pipe layout.

Hope this helps

Many thanks for your prompt reply.
Can I assume from your message that the solution would be to connect the 22mm piping directly to the Meter?
[automerge]1572259085[/automerge]
Many thanks for your prompt reply.
Can I assume from your message that the solution would be to connect the 22mm piping directly to the Meter?
(sorry if i've duplicated this reply, still learning how the message system works)

 

[Chuck]

His reply was that gas is different, “it’s all about volume not flow”.
Can anyone tell me if this is correct

IMO, it's not correct in this context. In this case, if it were "all about" anything, it would be pressure drop between meter and boiler.

There are differences between how incompressible fluids (such as water) and compressible fluids (such as gas) behave when flowing through pipes, etc. but simplified calculation methods of the type Brambles gave you are all that's needed for domestic installations.

 

[Brambles]

Spenbeck,

It is unlikely that 22mm would suffice from the lengths you have given. That is also assuming that you have no other gas appliances in the premises.

You installer needs to properly size and instal the pipework in accordance with the regulations.

In simple terms I would expect at least 50% of the installed 22mm pipe will require replacing with 28mm dia pipe -assuming of course that it is copper pipe.

I don’t want to be Dr Doom, but it can be quite dangerous if you have an undersupplied Combi and an old gas hob (with no flame safety device) on the same installation. The Combi on full load can starve the ignited hob of gas, once the combi goes off, the gas (unignited) flows back to the hob.

 

[townfanjon]

I have covered this on here before , yes the pipe increase will help the volume but doesnt actually mean the boiler will make the required gas pressure and gas rate correctly , the only way to get it right first time is by a pipe sizing calculation .

 

[Spenbeck]

Thanks once again for your help

 

[king of pipes]

Most definitely undersized brambles has got it we'll covered above don't be fobbed off 28mm minimum from the meter , Gas safe can do a site visit it only takes a phone call has the boiler been registered yet ?

 

[Spenbeck]

Not yet, installation only completed last Thursday

 

[king of pipes]

Tell your installer you intend to get the install inspected by gas safe see if he changes anything ? harsh words from one installer about another but we all need to stay working within the regulations I had this done to me and it will definitely make him less complacent , thankfully it all worked out . Good luck kop

 

[Spenbeck]

I will, how do I organise an inspection by Gas Safe?

 

[ShaunCorbs]

I will, how do I organise an inspection by Gas Safe?

Phone gas safe up and tell them your not happy with the gas pipework

 

[king of pipes]

Just ring em up say you are concerned about a recent install it will all go from there have all the information in front of you

 

[Spenbeck]

Thank you, I’ll call them in the morning.

 

[king of pipes]

Can you update us on the outcome of this please . Regards kop

 

[Spenbeck]

Update - I have raised a complaint with GasSafe and am waiting for them to call me to arrange a site visit. I will update again with their conclusion.