Do I need a 2nd gas meter or will upgrade suffice?

[ShaunCorbs]

Sorry I wasn't clear, I meant how did you calculate the 7m3h? But it's not that important as I know it will be over the U6 capacity.

Meter flow rates I got from previous, but the key question is: is there a limit on the volume of gas in the pipes, elbow, t's above which necessitates a 2nd meter, irrespective of whether the existing meter is a U6 or U16? And how is that calculated?
My installer says that the volume of gas in the system plus the new pipework (approx. 12m x 28mm) exceeds the capacity/allowance from one domestic meter, even if it's a U16. So I have to get a 2nd meter. I haven't seen his calculations.
In May this year you replied to a previous posting where a domestic engineer asked if he was allowed to work on a job where the gas volume calculation came below a certain number, and you did a calculation. But I can't find any mention, here or elsewhere, of a calculation of gas volume for a U6/U16 meter to see if I really do need a 2nd one.

Cadent /Nat. Grid are coming tomorrow to assess the supply pipe and I will ask if 80kW means I need a new pipe - hopefully not.

I guess he means it will be into commercial scope on your sized pipe work volumes

 

[DuncanM]

I came across something similar a while back and it was too big for me to do. Meter plus pipework ment I was unable to carry out the work due to the purge volume of the gas line. Maybe they are suggesting a second meter as this could be classed as two separate installations with two meters? Rather than say no to you they are proposing costing you more money than necessary. Best advice when it comes to such large installs, get a commercial engineer. They are qualified to install large diameter pipework and over 70kw.

 

[Cerendib]

That's figure referred to is more associated with pipework testing requirements above which an engineer has to be commercial qualified due to the procedures used.
It's not a figure that relates to the capacity / sizing requirements of a meter or system design.

OK I understand - not appropriate
[automerge]1572538971[/automerge]

I guess he means it will be into commercial scope on your sized pipe work volumes

Many thanks for all comments.

I have been doing a little research - time permitting - and the most useful info I have come across is from posters to this site! It's a great pity that very useful info an considered opinion and facts from experienced and knowledgeable engineers is hidden away in old posts and forgotten - there must be a way to hive off the most useful into a separate section so they can be referenced easily and updated when superseded, eh Mod?
Anyway, the first point relates to 'diversity factors' (Kirkgas - Jul 6 2012) when calculating max. flow rates. I'll leave you to look up the post, and the few prior for context.
But essentially: "...A diversity factor is given to each type of appliance according to the normal degree of intermittent of use. Where there is only one or two appliances (e.g. combination boiler and cooker) the diversity factor shall have a value of one. Where there are more than two appliances the diversity factors listed in Table A.1 shall be used."
Relevant bits from Table A.1: "Combination boilers 0.8, Hotplates 0.6..." (Taking mfr's Gross input values).
So in my case it is: (28 x 0.8) + (35 x 0.8) + (8 x 0.6) = 55.2 kW x 0.094 (easier way to conv. kW/h to gas rate - see Kirkgas's following post) = 5.188 m3/hr.
Which a U6 of 6m3/hr should be able to cope with. (So this seems to be saying: don't simply add up all kW of all appliances there's more to it).

Next, static volume of gas in pipework, less than 0.035 = domestic, greater than this = commercial. (Cadent engineer). My installer is giving me grief over this, I will shortly go over his calcs. with him, (he's been called for some 'emergency' commercial work in a hospital).
Add together ivp (installation volume of pipe) + ivf (installation volume of fittings) + ivm (installation volume of meter) to get total static volume of gas in system.
In my case this is: ivp= 16.1m of 28mm + 7m of 22mm + ivf= add 10% of ivp + ivm of U6 or U16 meter. (Similar to Tamz - Dec 21 2013)
=> 16.1 x 0.00054 (vol. of gas in 1m of 28mm) + 7 x 0.00032 (for 1m of 22mm) + 0.0010934 (10%) + 0.008 (for U6) or 0.025 (for U16 - Cadent engineer))
=> 0.0200274 m3 for U6 or 0.0370274 m3 for U16. So a U6 is OK but a U16 makes it in the commercial range.

So a U6 meter should suffice from both points of view.

If anyone knows different, eg. the figures are wrong / this ... has been superseded with this .... / the regs. .... say this..... / diversity factors no longer used, use this instead / etc., etc. Please let me know. (I am a little nerdish in needing to know figures and reasons behind procedures and actions, especially when asked to cough up £££'s more).

Btw. the Cadent engineer visited. Took one look at the set-up (basic U6 in the usual white box fitted to the outside of the house), took a photo and said '...yeah, upgrading to a U16 or fitting an additional meter to your supply would be no problem'. I asked if he needed to do any measurements, he said no, he could tell by looking the supply would be OK, no calculations required. When I rang the office they said '...we'll need a week to do the calculations and send you our report, you can't get it any quicker...' Happy days!

Thanks for reading.

 

[Brambles]

Cerenbid,

Unfortunately, you are referencing a calculation process that is not accepted by current GS(IU) Regulations for domestic premises.

The only methodology accepted is an empirical process defined by the regulations. The process uses the Manufacturer's stated net input for each appliance on the installation. Similarly pipework is also sized on aempirical basis.

The reason for this is that any competent engineer using the process will reach exactly the same answer for the installation.

I accept, that in physical terms the answer is not necessarily correct ( but a structured estimate) - but it gives uniformity across the industry in England and Wales. Irrespective of that, it is the only process that Gas Safe will accept.

Please take this comment in the spirit with which it is intended.

Proposing to instal a second U6 meter feeding the same dwelling ( that is not divided into flats) is unusual and raises alarm bells with any credible Gas Safe Engineer. Moving to a U16 (if that capacity is needed) would be the normal route to follow. This would probably move the classification of your installation from domestic to commercial.

If you wish, guides to the GS(IU) Regulations are available to buy ( circa £50) - they cover all the situations you are referring to in a simple straightforward manner, with lots of worked examples.

 

[ShaunCorbs]

Can’t really use diversity on two Combi boilers as there’s a good chance there both going to be running at full at the same time

As for the info it’s not for everyday joe blogs the information is easy to find if your a registered gas tech

My last post on the matter

 

[Cerendib]

Cerenbid,

Unfortunately, you are referencing a calculation process that is not accepted by current GS(IU) Regulations for domestic premises.

The only methodology accepted is an empirical process defined by the regulations. The process uses the Manufacturer's stated net input for each appliance on the installation. Similarly pipework is also sized on aempirical basis.

The reason for this is that any competent engineer using the process will reach exactly the same answer for the installation.

I accept, that in physical terms the answer is not necessarily correct ( but a structured estimate) - but it gives uniformity across the industry in England and Wales. Irrespective of that, it is the only process that Gas Safe will accept.

Please take this comment in the spirit with which it is intended.

Proposing to instal a second U6 meter feeding the same dwelling ( that is not divided into flats) is unusual and raises alarm bells with any credible Registered Gas Engineer. Moving to a U16 (if that capacity is needed) would be the normal route to follow. This would probably move the classification of your installation from domestic to commercial.

If you wish, guides to the GS(IU) Regulations are available to buy ( circa £50) - they cover all the situations you are referring to in a simple straightforward manner, with lots of worked examples.

Thanks for this info Brambles. So I guess the diversity factor is now not used and current regs. simply take the sum of net (not gross) input of all appliances.
I will try to get hold of a copy of the current GS(IU) Regulations to see how this and the total gas volume calculations are done.

I'll also have to get confirmation from Cadent re. what their engineer said about a second U6 meter or whether a U16 would suffice.

Thanks to all contributors for your input - with your help I think I have gone as far as I can with this.

So unless any one has any further comments, which I will answer if required, I'll say thanks again - and goodbye.

 

[Brambles]

No. All gas appliances should be CE marked. The CE mark defines the net heat input. That gives you a consistent measure for all appliances across Europe. From there, if required for the calculation, you convert the net to gross ( for natural gas multiply by 1.11) and proceed with the relevant calculations.

The GS(IU) Regulations are very prescriptive - if you follow them correctly, there is never a debate, it will give you a definitive answer.

 

[Cerendib]

No. All gas appliances should be CE marked. The CE mark defines the net heat input. That gives you a consistent measure for all appliances across Europe. From there, if required for the calculation, you convert the net to gross ( for natural gas multiply by 1.11) and proceed with the relevant calculations.

The GS(IU) Regulations are very prescriptive - if you follow them correctly, there is never a debate, it will give you a definitive answer.

OK.
I did see the multiplication of the net by 1.1 to get gross by topdog (post following kirkgas's referred to above) but he did suggest it was only if mfr's gross figures were not available.

The only regs I seem to be be getting up, from multiple locations, are Gas Safety (Installation and Use) Regulations 1998 (GSIUR) as amended. Approved Code of Practice and guidance (from Gas Safety (Installation and Use) Regulations 1998 (GSIUR) as amended. Approved Code of Practice and guidance) which is very prescriptive on the safety rules but gives no figures or examples, could you give me a link or an actual publication title to look for?

Thanks for your help.

 

[Brambles]

There are a number of manuals that describe the working of the GS(IU)Regulations, they are all around £50 to £60.

NICEIC Domestic Gas Safety Parts 1 and 2
BPEC Core Domestic Gas Safety
Logic Certification Gas Safety Training Manual

plus others, but they are all in a very similar format reflecting the GS(IU)R into real life situations.

With respect to rated capacity. CE rules determine that the legally required number is the Manufacturer's stated net input in KW.

All gas appliances currently sold in the UK must be CE marked.

Having said the above, my advice remains to find a local reputable Gas Safe Registered installer who can talk you through the process and develop a cost effective solution for you. That is what they are trained (and legally registered) to do.