interesting question regarding two flats two metres one consumer unit

[chi won]

interesting question regarding two flats one consumer unit
hi a quick question. there is a property which is split in two flats.
at the moment they share the electricity bill. there is one meter and one consumer unit.
thinking ahead if we want to add two submeters. for example two coin metres. but then normally would have two consumer units but there is no space for that as it is extremely tight space. so the consumer unit currently is just large enough to insert two 100a sw switches. and have two rcd's and just enough mcb's for the two flats. although it maybe a strange situation. but my question is purely to satisfy the regs. is there any issue with having the two sets of meter tails entering the consumer unit and connecting with the two independant 100a sw switches inside the consumer unit.

 

[littlespark]

Downright dangerous.

an electrician can’t work one side of the board without isolating the other.

are these seperate flats, or HMO rooms?

ideally each flat should have its own supply, own meter, own consumer unit, and the CU should be within the property so the occupant can reset tripped breakers.

 

[westward10]

Multi tariff consumer units have more than one set of supply conductors however adapting a unit to suit your need is likely to go beyond the manufacturers recommendations.

 

[brianmoooore]

Multi tariff consumer units have more than one set of supply conductors however adapting a unit to suit your need is likely to go beyond the manufacturers recommendations.

It would be far from an ideal solution, but I can't see how it would be outside the manufacturer's recommendations.

 

[timhoward]

I believe that under 536.4.203 the person assembling and using a CU in this way would essentially become the manufacturer with associated obligations.
It wasn't originally designed for more than one supply to it.

 

[brianmoooore]

It wasn't originally designed for more than one supply to it.

Dual tariff ones are. Often fed from two meters as well.

 

[Lucien Nunes]

BS7671 requires equipment to be designed so that it can be isolated for maintenance. Interruption of the supply to one property to work on another is not reasonable and would not count as suitably designed for this purpose, so I would consider it non-compliant.

Dual-tariff boards may have two supplies but serve one property, so both can reasonably be isolated for maintenance on either section.

 

[brianmoooore]

One house into two flats. One property or two?

 

[timhoward]

Dual tariff ones are. Often fed from two meters as well.

I see what you mean but they tend to be quite large and we've heard that space is limited, hence my assumption that converting a CU was the intention.

One house into two flats. One property or two?

It sounds like two households if two coin meters.
Probably the same answer as one council tax bill or two?

 

[pc1966]

How many circuits do the flats actually need?

Could you use two of the larger "garage CU" side by side with the RCCB acting as the main switch?

 

[Rockingit]

If space is an issue, as also are issues of things like one point of isolation etc etc... thinking outside the box a bit here but you could use a double stack board, so a separate DIN rail for each place and have a simple 1ph DIN meter on each as well. You could, maybe (haven't fully thought this one through..) fit a simple remote switch in the second flat to trigger a shunt trip in order to isolate for emergencies. But nothing will ever resolve not being able to reset a trip when the neighbour's not there....

 

[pc1966]

Looking over the other comments, it seems that @littlespark has a very good point that the CU should be accessible by the flat occupants in case something trips and the other flat occupants are on holiday, etc. In that case you can take a sub-main off a fused-switch to a new CU and coin meter in another location so the cramped space is less of an issue.

Unless all of this is in some communal entrance?

I would also suggest that the flats are checked very carefully to make quite sure that they do not share any circuits. I.e. there is not some socket in flat #2 spurred off a ring in flat #1 so you have a dangerous situation if someone in #2 switches their CU off completely to isolate and finds something still live as fed from #1. Same for the risk of a "doubly borrowed" neutral if there are upstairs/downstairs lights on both CUs, etc.

Not to mention the possible legal fall-out if someone find that an unknown percentage of their bill has been used by the others over years!

 

[westward10]

Dual tariff ones are. Often fed from two meters as well.

It is not so much it has two separate supplies more the fact the configuration is being altered beyond the manufacturers intention.

 

[chi won]

thank you all for your inputs. i am looking through them and digesting.
sorry forgot to mention that it is one house converted to two flats so the consumer unit and meters ect are all in a communal area.

 

[chi won]

Looking over the other comments, it seems that @littlespark has a very good point that the CU should be accessible by the flat occupants in case something trips and the other flat occupants are on holiday, etc. In that case you can take a sub-main off a fused-switch to a new CU and coin meter in another location so the cramped space is less of an issue.

Unless all of this is in some communal entrance?

I would also suggest that the flats are checked very carefully to make quite sure that they do not share any circuits. I.e. there is not some socket in flat #2 spurred off a ring in flat #1 so you have a dangerous situation if someone in #2 switches their CU off completely to isolate and finds something still live as fed from #1. Same for the risk of a "doubly borrowed" neutral if there are upstairs/downstairs lights on both CUs, etc.

Not to mention the possible legal fall-out if someone find that an unknown percentage of their bill has been used by the others over years!

thank you again for your inputs.
so it seems to summarise that a duel/multi tariff would be ideal as ultimately there are two supplies coming in to the cu. obviously to work on the cu would require turning off power to both but that is a practicality (perhaps a nuisance) but nothing dangerous
as it is in the communal area there are no worries of one flat not being able to access the others supply for safety. once again a mean tenant can mess around with his neighbours supply as it is in the communal area but that is a practicality but not dangerous.
i agree the flats should be checked. but ultimately even if there was one socket in one flat that actually spurred off from the other flat the only major downside would be the bills that he is using free electricity. but i do get the danger of one person thinking the whole power is off in his flat when in reality it is not.

what about another possibility of an external 100a dual pole switch placed before the sub meters and then no 100a switch in the consumer unit itself. so the tails from the sub meters would connect straight into the rcb's and then can use a garage consumer unit. would that be an option?

 

[pc1966]

what about another possibility of an external 100a dual pole switch placed before the sub meters and then no 100a switch in the consumer unit itself. so the tails from the sub meters would connect straight into the rcb's and then can use a garage consumer unit. would that be an option?

It would be an odd arrangement, safer as everything in the CU would be off for any work, but hardly considerate to the other flat's occupants.

How much space do you actually have for the meters and CU(s)?

How many circuits does each flat require?

 

[MrPupsi]

Could easily swap the current board over for a couple of small RCBO boards, judging by your diagram.

No point messing about when it can be done properly.