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