boiler distance from gas meter,, help

stevefatboy · 11 Apr 2009

hi, im having a new ariston 28kw fitted in kitchen.the meter is 37m away from the boiler including bends ,which i have allowed .5 meter for each bend.it already has agas line of 22mm,do i need to up grade it to 28mm, i have a gas hob on same line,1 corgi man says you need 28mm other says you can get away with 22mm, help !!!!

kevindgas · 11 Apr 2009

we would need the rating of the hob as well as the boiler and what distance of pipework was shared to answer correctly.

I would think that some of the pipe may need upsizing to 28mm

kevplumb · 11 Apr 2009

,1 corgi man says you need 28mm other says you can get away with 22mm, help !!!! icon_rolleyes.gif icon_eek.gif

you "don't get away " with sizing pipework

swbjackson · 12 Apr 2009

A 28 Kw boiler requires almost 3 cu m of gas an hour. The maximum length of 22 that will pass that much gas is around 2om. Considering you've got a hob I would say that most of it needs to be 28.

Pass the guy that says 22 is alright his Stetson as he leaves.

bengasman · 12 Apr 2009

Quick look at the tables shows 37 meteres in 28 mm gives about 3.7 m3, just enough for your boiler and a modes hob if all joints are neatly deburred. and that is something a lot of plumbers don't bother doing.
I would advice to do the first bit in 35 if it is easy to fit, to allow for additional gas use if you decide to add/upgrade an appliance.

Agile · 12 Apr 2009

Why not do the last bit in 35 mm ?

Tony

bengasman · 12 Apr 2009

Bit of guesswork.
At that length, I guessed the first bit would be a long run under the floor. Easy to do and no need to hide it.
Have you ever tried suggesting to the lady of the manor that you were going to stick a 35 mm gaspipe on the wall in her kitchen? I wouldn't if I were you.

Agile · 12 Apr 2009

It would be a very big house if it was 37m from one part to another!

More likely to be an upstairs flat with external meter.

A transition to a larger pipe gives less restriction than a transition to a smaller pipe!

Not much difference but...

Tony

gas4you · 12 Apr 2009

As you have 2 appliances, then the length of pipe that has to carry the gas for both of these needs to be doubled for your calculation as a starting point.

bengasman · 12 Apr 2009

Agile said:
Not much difference but...

Tony

The difference is:....... drinking the coffee or wearing it.

Forget all the technical relevances.
I am NOT going to suggest to her indoors to stick a great big f... off 35 mm pipe on Her Kitchen wall. NO. Not me. You do it.

I have already lost most of my hair, I don't want to loose most of my teeth too.

bengasman · 12 Apr 2009

gas4you said:
As you have 2 appliances, then the length of pipe that has to carry the gas for both of these needs to be doubled for your calculation as a starting point.

Erh, how do you work that one out Dave?

Agile · 12 Apr 2009

He was basing that ( wrongly ) on both the boiler and the hob using the same power!

Very roughly as the hob might use about 10kW max and the boiler 30 kW then as a rule of thumb he could increase the pipe length by 33% to make 50 m effective length based on a 30 kW load.

That would be very muddling though but it serves to show just how wrong the installer who said the 22 mm gas pipe would be!

Without calculating I would guess that about 25m would need to be in 32 mm.

Tony

bengasman · 12 Apr 2009

Agile said:
...Very roughly as the hob might use about 10kW max and the boiler 30 kW then as a rule of thumb he could increase the pipe length by 33% to make 50 m effective length based on a 30 kW load....

Tony

Still an odd way of doing things.
I find a lot simpler to add the 10 and 30 up, and check the tables for a 40 kw load.
Pipe requirements for 20 metres of 40 kw are not the same as 40 metres of 20 kw, hence increasing the length to compensate for a higher load could lead to using the wrong size.

I must admit usually not bothering with calculations.
Very rough guesstimate, if the result is anywhere near borderline ( within about 20%) I simply ask the client if he would be interested in getting the next size up to allow for future upgrades/additions at 10% increase of price for the gaspipe.
Still need to meet the first one that says: "no, I don't want double the capacity for 10% more money."

gas4you · 12 Apr 2009

Not basing that (wrongly) on both using the same power, just going by the book.

Obviously something you have forgot to read of late Tony

If 2 appliances are installed the pipe work must give only 1/2 mbar drop for each, if 3 then a 1/3 rd each etc etc.

Have a look in the essential gas safety book.

Agile · 12 Apr 2009

gas4you said:
If 2 appliances are installed the pipe work must give only 1/2 mbar drop for each, if 3 then a 1/3 rd each etc etc.

Have a look in the essential gas safety book.

If it really says that then I would question if its correct!

What has changed so that each one can no longer get meter pressure -1 mB or less drop with both appliances on?

Where are the gas trainer/assessors?

Tony

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boiler distance from gas meter,, help

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