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

[Cerendib]

Hello - I would appreciate your help on the question of whether I need a 2nd gas meter.

At present I have a U6 meter serving a WB combi 28kw, a gas hob 8kw (downstairs) and a 49 yr old Glow-worm boiler (14kw) (upstairs).
The Glow-worm boiler has finally packed up and has been disconnected as it has started leaking gas.
I am replacing this with a Vaillant combi 35kw.
As I understand it this now totals 71kw which exceeds the U6 meter capacity so an upgrade to U16 is planned.
I suspect the supply to the meter to be adequate (as I had an informal chat to one of the installers when they were putting in meters for the road
a couple of years ago) - I have also booked a Cadent (London) survey to check.

So, assuming the supply to the meter is adequate for a U16, my questions are:

1. The (max) figs for U6 are 64 kW and the flow rate is labelled as 6m3/hr although he has measured it currently as lower (I forget the number), what are the numbers for a U16?
ie. Will the U16's flow rate or volume output be sufficient for the two combi's and the hob? (I suspect the kW is OK).

2. My gas boiler installer says no and I will have to have a second gas meter to cope with the volume of gas required.
He has done various calculations using pipe lengths, elbows, T's into account. I think he is allowing for 20m of 28mm copper pipe
from meter to both boilers in both locations, (although about 8 of this is 22mm), plus various amounts for elbows and T's. What are the calculations involved and is he right?

3. The installer says that my only alternative if I want to only use one meter is to fit a commercial meter, is he right? (I am worried that he is leaning to the commercial side with his calculations - he has done a lot of commercial work)

I would really like your input and a 2nd/3rd opinion as both these alternatives are worrying me.
A commercial meter is out of the question - I am a pensioner on a basic state pension - and it is only for domestic use.
I really want to avoid a 2nd meter as the running costs (2nd meter standing charges) would be a constant expense for which I would have to make big sacrifices, my supplier is currently to get back to me with an installation cost, (which I'm sure will not be cheap).
My supplier also says that to change the U6 to a U16 will be free and the standing charge would stay the same irrespective of meter.

Your help would be greatly appreciated.

Many thanks.

 

[ShaunCorbs]

I’m guessing a house converted into two flats ??

Also why the 35kw boiler when the old one was 14kw so 25-28kw

This would put you under a u6 meter

 

[snowhead]

How big is this house and as per Shaun is it split with 2 households.
71kw capacity of heat is a lot for a single dwelling.
I'm confused as to the suggestion of 2 meters otherwise.

Is the 35kw combi just to get a good hot water flow rate?

Re the flow rate, the clue is in the title of the U.16 meter.

 

[Brambles]

I suspect that the installer is proposing a second primary meter installed in the property, because he/she wants it located close to the second boiler. Whilst a meter upgrade to U16 is free, the installation of a second primary meter is not - and it is not cheap either.

Establish with your installer exactly what he / she is proposing and the size (diameter) / extent (and price) of pipework from the meter to the boiler location.


Points made in previous posts reference boiler sizing are absolutely key to resolving this issue in a cost effective manner.

 

[Cerendib]

I’m guessing a house converted into two flats ??

Also why the 35kw boiler when the old one was 14kw so 25-28kw

This would put you under a u6 meter

Hi - thanks for taking time out to reply.

No the house is not converting. I have my daughter her husband and children (and other relatives) coming to stay regularly and my son comes for extended periods to help out so they all stay upstairs. It is in fact the only place where the family, including ones from abroad, can meet and stay together.

The old one was 14kw but many years ago we put in an Ascot water heater for the hot water for the one bathroom, (not sure of the exact reason but probably because the hot water from the Glow-worm was not working so well, eg. not enough pressure/not hot enough/etc.) and it was probably a cheaper/better solution recommended to us 30 odd years ago than replacing the heavy floor-standing cast-iron boiler - as I say I can't remember the exact reasons. Anyway, we replaced the Ascot water heater about 2 years ago when visitors kept mentioning they smelt gas when they came in the house - although no one in the house smelt gas. A plumber tested the Ascot and said there was a very small escape and we should think of replacing the Ascot as parts were not available to fix it. At the time the Glow-worm boiler (used for heating) was working fine. In fact, although I knew nothing about this, the replacement water heater has a nominal heat input of 30kw - so this takes us over the U6 max. (28+8+14+30). It was a large company that installed it and they never even mentioned anything like this to me.

35kw is a bit large I agree and 28kw would be sufficient for upstairs but we do have a loft that was in a very bad state (loose slates/gaps, badly insulated/difficult and dangerous to move around in/etc.) but a good large space. So I, with help of course, am converting it (very slowly) into a usable two rooms with bathroom, so I didn't want to install yet more appliance up there but thought to use the connections from the upstairs boiler, hence a boiler with a larger capacity.
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How big is this house and as per Shaun is it split with 2 households.
71kw capacity of heat is a lot for a single dwelling.
I'm confused as to the suggestion of 2 meters otherwise.

Is the 35kw combi just to get a good hot water flow rate?

Re the flow rate, the clue is in the title of the U.16 meter.

How big is this house and as per Shaun is it split with 2 households.
71kw capacity of heat is a lot for a single dwelling.
I'm confused as to the suggestion of 2 meters otherwise.

Is the 35kw combi just to get a good hot water flow rate?

Re the flow rate, the clue is in the title of the U.16 meter.

Hi Snowhead thanks for replying.

The house is 2 floors with an attic space.

71kw does seems a high figure but it is an old Victorian house with quite a few room, some small. and it is only 2 combis and a 4 burner hob in the kitchen.

The 35kw is to get a good flow to all rads + hot water + for attic conversion (eventually).

So that means a U16 has a max. flow rate of 16m3/hr ? And what about this gas volume thing that the installer keeps talking about as the reason we need a 2nd meter?
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I suspect that the installer is proposing a second primary meter installed in the property, because he/she wants it located close to the second boiler. Whilst a meter upgrade to U16 is free, the installation of a second primary meter is not - and it is not cheap either.

Establish with your installer exactly what he / she is proposing and the size (diameter) / extent (and price) of pipework from the meter to the boiler location.


Points made in previous posts reference boiler sizing are absolutely key to resolving this issue in a cost effective manner.

Hi Brambles - The proposal is to put the 2nd meter next to the first outside the front door.
At present the (28mm) piping from the existing meter turns one corner, runs along the alley and into the house under the stairs then goes under the floor to the d/s boiler.
The (28mm) piping to the new Vaillant combi is proposed to run parallel to the existing then run vertically up the wall in the alley and across for about a metre and through to the wall mounted Vaillant. Total distance 6m.
Yes, although I am still waiting on a price from my supplier, I think a second meter will not be cheap.

The installer has given me a fixed price for the whole job parts and labour and I have no problem with that.
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I suspect that the installer is proposing a second primary meter installed in the property, because he/she wants it located close to the second boiler. Whilst a meter upgrade to U16 is free, the installation of a second primary meter is not - and it is not cheap either.

Establish with your installer exactly what he / she is proposing and the size (diameter) / extent (and price) of pipework from the meter to the boiler location.


Points made in previous posts reference boiler sizing are absolutely key to resolving this issue in a cost effective manner.

Sorry - didn't add up correctly: total external distance is 12.1m (+/-) of 28mm copper pipe with 3 elbows.

 

[Brambles]

Cerendib,

You need to get a decent heating engineer to review the complete requirements for your property and put some credible recommendations to you

If you are oversizing a boiler because the house is leaking hot air and is poorly insulated - you will get far better value by investing in insulation and draughtproofing, rather than spending money on excessive gas consumption. As an order of magnitude, 70kw of gas fired heating at full tilt is going to burn gas at the rate of around £2.80/hr.

A properly configured 35kw boiler, with the correct smart controls should be more than capable of providing heating and hot water for a large properly where a number of the rooms are not in regular use.

Apologies if this sounds rather blunt,

 

[ShaunCorbs]

Why not just use one boiler now large enough for both properties and an unvented cylinder if your mains will take it

 

[Stu-B]

There’s better ways of managing your hot water and heating requirements than just sticking in the biggest boilers, I’d be more inclined to pair 2 smaller boilers together and go with an invented cylinder for hot water and maybe a pumped accumulator if your mains supply isn’t sufficient. As brambles has suggested, get a decent local heating engineer in to give you a design quote, and look into your homes insulation too. It’ll save you plenty in the long run

 

[king of pipes]

I agree with the above better to improve the heat loss of the property adding as much insulation as possible batten and insulate the walls , there are companies that can spray insulation directly onto tiles from inside the loft space , replace the windows and doors for better thermal efficiency , as Stu has said better to install a pair of boilers a 300 litre unvented cylinder and a pumped accumulator 60kw should be enough for said property if designed properly pipe sizing must be calculated to achieve the required supply for the boilers 28mm is undersized . Kop

 

[Cerendib]

Cerendib,

You need to get a decent heating engineer to review the complete requirements for your property and put some credible recommendations to you

If you are oversizing a boiler because the house is leaking hot air and is poorly insulated - you will get far better value by investing in insulation and draughtproofing, rather than spending money on excessive gas consumption. As an order of magnitude, 70kw of gas fired heating at full tilt is going to burn gas at the rate of around £2.80/hr.

A properly configured 35kw boiler, with the correct smart controls should be more than capable of providing heating and hot water for a large properly where a number of the rooms are not in regular use.

Apologies if this sounds rather blunt,

Cerendib,

You need to get a decent heating engineer to review the complete requirements for your property and put some credible recommendations to you

If you are oversizing a boiler because the house is leaking hot air and is poorly insulated - you will get far better value by investing in insulation and draughtproofing, rather than spending money on excessive gas consumption. As an order of magnitude, 70kw of gas fired heating at full tilt is going to burn gas at the rate of around £2.80/hr.

A properly configured 35kw boiler, with the correct smart controls should be more than capable of providing heating and hot water for a large properly where a number of the rooms are not in regular use.

Apologies if this sounds rather blunt,

Thanks for your repy - and also to ShaunCorbs, Stu-B, and king of pipes - your views are appreciated.

However, you are all viewing the heating/hot water problem from a whole house review perspective, there are practical as well as financial difficulties with this.

The d/s combi is working fine and less than 10 years old. The d/s c/h is separate from the u/s and has always been so from when the heating was put in so to re-design the heating/hot water for the whole house as one would mean removing the boiler, joining the two systems (if this was posible or practical), with the probable disturbance to the small-bore pipework and consequent leaks under the floorboards - the disruption, time and expense of this let alone the trouble of removing whole rooms's worth of contents to take up floorboards is simply not worth it. The pipework for the d/s and u/s was put in with the original c/h and boilers nearly 50 years ago and is micro-bore (10mm) as that was the way it was done, (much more malleable and easy to sweep bends so eliminating need for most t's and elbows - amongst other reasons I'm sure) and we have had no problems with the pipework. Throughout the house where we have replaced rads we have replace pipework with 15mm but he majority is still 10mm. I have spoken to other heating engineers about this option some 3-4 years ago, The (current) installer, (he does call himself a 'heating engineer' - am I denigrating his job by callling him an 'installer'? I have avoided calling him just a 'plumber' for this reason), has recommended that he does not power-flush the system because his certainty that the pipework will not take it. As for being decent - he is courteous, friendly - and polite!

I am not "oversizing a boiler because the house is leaking hot air and is poorly insulated", the house is (almost) as well insulated as it can be. All windows and external doors are double glazed, all external walls where we have re-decorated the rooms (most of them) are internally insulated, the loft is going to be insulated (floor/walls/roof) shortly (local authority grant) even before we convert it, and there are no draughts.
This is an old Victorian house with many internal plasterwork features so internal insulation not always complete unless we cover these up completely and remove all character of the room but we have done as much as is possible. With solid walls, it is theoretically possible to fit external wall insulation but is extremely expensive and may not be allowed as it would reduce the alley width between houses on either side (I'm certain the neighbours would object) - and completely ruin the front bay windows - even if the local authority approved.

As for excessive gas consumption this is a false assumption: our gas consumption is not likely to rise. The u/s will be used to the same extent as it has always been used by the same number of people for the same frequency. When, and if, the attic is fully converted we may have a couple more persons up there using the heating/hot water and this may or may not be for extended periods. If this results in much bigger consumption then yes we'll have to find a way of meeting this, or re-evaluating the usage, but I am simple trying to give ourselves the best option without having to end up with a converted unusable space which cannot be used at a later date.

Anyone used this gas volume calculation (see earlier) when considering meter capacity?

 

[ShaunCorbs]

Your requirements with the set up you’ve suggested is 7m3h so outside capacity of a u6

Roughly to get the gas meter changed to a u16 is around £5k last quote I had 3 months ago

If it was me I would do the whole system and do it right once

 

[Brambles]

Cerendib,

Many thanks for taking the time to explain the background and the reasoning behind your plans for the way forward.

I think you can only be guided by a good local heating engineer who has seen the property first hand.

Just have in mind that the service providers for Gas are not regulated in the same way as the providers for electricity / water or sewage who have imposed ceilings on the maximum charges that they can levy. With Gas they charge the actual costs to either connect or make changes to an installation.

Shaun is far more experienced in these matters than I am, but I have never had a quotation from a Gas service provider for amending a Gas meter location that I thought was anywhere near reasonable. My last one was £3,640 to move a U6 meter 35 feet. You also have to pay them to remove it as and when in the future.

I hope that you have found the comments from those who responded to you useful and informative,

 

[Cerendib]

Your requirements with the set up you’ve suggested is 7m3h so outside capacity of a u6

Roughly to get the gas meter changed to a u16 is around £5k last quote I had 3 months ago

If it was me I would do the whole system and do it right once

Yes I believe you are right, my installer said as much although he did not give me a figure for the flow, btw how do you calculate this?

My supplier (ESB) have told me when I made a phone enquiry that they do not charge for replacing a U6 with a U16.
Later I asked them about the charge for a 2nd meter, which they said they would email me, and asked at the same time to confirm there was no charge for the meter upgrade - still waiting on their email.
Hope they won't decide to change their mind.

Still puzzled about this gas volume business, won't the U16 be able to deal with higher volume requirements than a U6, or is the type of meter irrelevant?
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Cerendib,

Many thanks for taking the time to explain the background and the reasoning behind your plans for the way forward.

I think you can only be guided by a good local heating engineer who has seen the property first hand.

Just have in mind that the service providers for Gas are not regulated in the same way as the providers for electricity / water or sewage who have imposed ceilings on the maximum charges that they can levy. With Gas they charge the actual costs to either connect or make changes to an installation.

Shaun is far more experienced in these matters than I am, but I have never had a quotation from a Gas service provider for amending a Gas meter location that I thought was anywhere near reasonable. My last one was £3,640 to move a U6 meter 35 feet. You also have to pay them to remove it as and when in the future.

I hope that you have found the comments from those who responded to you useful and informative,

Absolutely no problem Brambles. My view is that if I want anyone to bother to take their time time to read, consider and reply giving me the benefit of their knowledge and experience the least I could do is to inform them of the facts as I see them. I realize my posts have been somewhat long and considered editing them down but I feel that the more (relevant) info I give the more able others are to give more informed advice.

I will bear what you say in mind re. gas supplier charges. I am waiting for their email regarding this (as I mentioned above to Shaun).

I have indeed found all comments useful and informative and am fully appreciative of all who have taken the time, it has been and continues to be an interesting - and steep - learning experience.

 

[ShaunCorbs]

add all your appliance up

eg

wb 28kw
new boiler 35kw
gas hob 8kw
+ 10%

=78kw required so 80kw thats what you tell the gas / networks people you need a supply capable of ^^

not just the gas meter that needs to be upgraded chances are the supply pipe eg the pipe from the main to the gas meter (supply side) will need to be increased hence the charge

as for meters

u6 = 6m3h/h
u16 = 16m3/h

 

[Cerendib]

add all your appliance up

eg

wb 28kw
new boiler 35kw
gas hob 8kw
+ 10%

=78kw required so 80kw thats what you tell the gas / networks people you need a supply capable of ^^

not just the gas meter that needs to be upgraded chances are the supply pipe eg the pipe from the main to the gas meter (supply side) will need to be increased hence the charge

as for meters

u6 = 6m3h/h
u16 = 16m3/h

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.

 

[snowhead]

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.

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.

 

[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
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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.

 

[Cerendib]

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.

On the basis that one opinion is good but two is better, I have just got two separate (Gas Safe Registered) plumbers to have a look and give me their advice. One said I'd need a separate supply feeding a second U6 meter, the other said replacing the U6 with a U16 would be sufficient; together with my installer who thinks the current supply is good enough for a second meter and the Cadent engineer who gave both views I have no shortage of (differing) opinions. Hmmm.
Since my gas supplier has already told me that a U16 meter would still be within a domestic tarif I know which option I'd prefer.

Many thanks Brambles for the above manuals info, will try to locate them and do some calculations myself for my own piece of mind if nothing else.