Two Flats, Two Boilers, One Meter?

[Nino]

Hi all,

I'm hoping to pick some-ones brains here as I haven't done much servicing since my apprenticeship and training days having worked for a company and been employed mainly as an installation engineer.

Since starting up on my own I am doing more servicing and repair and today went to a job that threw me a bit.

The property is a 3 bed terrace that has been converted into two flats. There is a combi boiler in each flat but only one pre-pay Quantum gas meter situated outside. There is 28mm off the meter which continues into bottom flat and changes down to 22mm for top flat.
Load is my primary concern here-I can obviously work it out but was sure you need two meters. So I came home to consult the book and seem to have found diagram of typical installation for two flats which seems to require two meters for two flats. Which is what I thought. Can't seem to find anything definite though to report back to landlord with.
Any advice/experience greatly appreciated!

[dancinplumba]

hi and welcome are, you an rgi ??

[Nino]

Thanks and yes I am Gas safe registered!

[kirkgas]

a meter is only a device for someone to be charged for the gas used, so depending on how the building is split then one meter is adequate, there will be one bill sent to the person who is listed as the customer and its up to them to decide how the gas bill is actually split if it gets split, there are plenty of properties that have a granny flat with the bill being paid by the householder.
re the load a U6/E6 meter will supply gas to a total of about 63kw so its easy to work out whether the meter will supply boilers and cookers if there are any, after that you need to look at the supply pipe to ensure it is adequately sized and split to supply the boilers, only having one meter is fine ( you cant have a quantum as a primary meter if you have a secondary meter fitted, but if there is only one meter it will be fine)

[Howsie]

Who pays for the gas out of interest?

[bennygas]

kirkgas is quite right, you need to mindful of the pipe sizing, and meter capability, and I would also suggest that you're mindful of the correct positioning and provision of ECVs within the property, also, would the tech bulletin re fsds on hobs/cookers apply here - cant remember.

On the meter capability, the total heat input of the appliances permitted on the meter is subject to diversity factors - there's this in BS6400-1:2006. Annex A, Section A.1

"A diversity factor is given to each type of appliance according to the normal degree of intermittent use. Where there is only one or two appliances (e.g. a combi and a 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.

Table A.1

Appliance Diversity factor

Central heating appliances (other 1
than combis)

Unit heaters 1

circulators 1

combination boilers 0.8

instantaneous wtr htrs 0.8

sink wtr htrs 0.6

room htrs 0.6

tumble dryers 0.6

hotplates 0.6

ovens 0.6

cookers 0.4

refrigerators 0"

So the idea is that if you've got a 30 kW combi, the heat input load on the meter is given by:

30 (Heat input in kw) x 0.8 (diversity factor) = 24kW

You go through and repeat this calculation for each connected appliance and then add all these kW's together. That gives you the total energy load. You then convert this to MJ/h (1kW=3.6MJ so multiply your kw by 3.6), then you need to convert the MJ/h into m^3/h, which can be done by dividing your answer by the CV of the gas involved, i.e. 39MJ/m^3 for nat gas.

[bennygas]

i wonder where the ground lies with regard to having a quantum meter supplying two flats - if the thing runs out due to heavy use in one flat, and a hob with no fsd is on in the other flat, then first flat puts more credit on...isn't this the same situation that was hoped to be addressed by having no secondary meters after a quantum primary?

[kirkgas]

kirkgas is quite right, you need to mindful of the pipe sizing, and meter capability, and I would also suggest that you're mindful of the correct positioning and provision of ECVs within the property, also, would the tech bulletin re fsds on hobs/cookers apply here - cant remember.

On the meter capability, the total heat input of the appliances permitted on the meter is subject to diversity factors - there's this in BS6400-1:2006. Annex A, Section A.1

"A diversity factor is given to each type of appliance according to the normal degree of intermittent use. Where there is only one or two appliances (e.g. a combi and a 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.

Table A.1

Appliance Diversity factor

Central heating appliances (other 1
than combis)

Unit heaters 1

circulators 1

combination boilers 0.8

instantaneous wtr htrs 0.8

sink wtr htrs 0.6

room htrs 0.6

tumble dryers 0.6

hotplates 0.6

ovens 0.6

cookers 0.4

refrigerators 0"

So the idea is that if you've got a 30 kW combi, the heat input load on the meter is given by:

30 (Heat input in kw) x 0.8 (diversity factor) = 24kW

You go through and repeat this calculation for each connected appliance and then add all these kW's together. That gives you the total gas load. You then convert this to MJ/h (1kW=3.6MJ so multiply your kw by 3.6), then you need to convert the MJ/h into m^3/h, which can be done by dividing your answer by the CV of the gas involved, i.e. 39MJ/m^3 for nat gas.

a quicker way is to multiply the total kw input by 0.094 to give m3/hr, but after totalling the HI as long as its under 63 kw it will be ok

[bennygas]

the only reason I brought it up was because if you've got a couple of decent sized combi in a house, plus a few other bits, the diversity factors are good to know about. it's come in handy for me once or twice.

[SimonJohns]

I must admit that I don't care about diversity factors.

If I have 75kw in a house. A u6 is undersized. Not worth the risk for the drop in pressure when all in use.

If there was a flueless fore there you would really risk someone's life

[bennygas]

quite agree. but the fact of the matter is, regardless of opinion to some extent, if this is what the standards say, it's what they say, unless there were some other grounds for invoking the unsafe situations procedure, it's kind of beyond our remit if you like. if an engineer had a customer who was clued up (don't ask me why they would be), and that engineer shut them off on these grounds. the engineer could come unstuck in a legal sense - other than a gut feeling that "it ain't right", and some standards saying it is right, he's on a sticky wicket. don't get me wrong - it is quite hypothetical. I quite agree that pipe sizing is likely to have to be spot on with that gas load though, and it's highly unlikely to be spot on. the index would fly round.

[Nino]

Who pays for the gas out of interest?

The tenants are friends and have amicable agreement!! One is away a lot which also concerns me. Thanks all for your v helpful posts