- Thread starter Roogy1
- Start date
Can you give a bit more information. It sounds bit odd.
We have an existing three-phase supply into a building and 3 meters connected to it. However these meters supply 5 services (4 x flats and 1 x landlord supply) so we requested the supplier to install a Bemco or similar unit and provide two additional circuits and two MPAN's so we can have each of the 5 services metered separately. Their solution is to replace the current 3 phase cable coming into the building with a larger one-although three electricians have confirmed the current cable is more than adequate for the user requirements and has been serving the building for 20 years plus. The operator has come up with numerous reasons why they cannot split this existing supply or use the existing cable and contradicted them selves which I have evidence of. I therefore suspect that their objective is to upgrade their network cable at my expense.
This won't help the OP much, but my only comment is that the vast majority of electricians (myself included) would not be conversant with the DNO rules or the parameters they have to work within, and probably therefore not in a position to comment with any authority on the suitability of the supply cable. I know enough to be aware that they are very different rules to the standards we work to, and it's very common to see a thinner cable coming into the property than the one we are obliged to fit where our regs start (the meter tails).
It might also be the case that everything was indeed ok 20 years ago, but any modification has to meet latest standards and things have changed.
That said, there are members on here that do work or have worked for DNO's and they are the exceptionally rare breed that understand both sides of the 'fence'. I hope you can find a resolution!
It might also be the case that everything was indeed ok 20 years ago, but any modification has to meet latest standards and things have changed.
That said, there are members on here that do work or have worked for DNO's and they are the exceptionally rare breed that understand both sides of the 'fence'. I hope you can find a resolution!
I've had experience of a DNO trying to charge me £3000+ for essential work that was their responsibility, so I can certainly believe the OP.
I believe the OP too, in fact I thought of you @brianmoooore when I read it.
My intended point was that adding a fourth electricians opinion might not help much unless the fourth electrician is uniquely placed to be able to discuss it with the DNO using the DNOs own terms of reference.
My intended point was that adding a fourth electricians opinion might not help much unless the fourth electrician is uniquely placed to be able to discuss it with the DNO using the DNOs own terms of reference.
I have worked for a couple of DNOs, not actually in the lv connection area, but am generally aware of the rules/guidelines and so on.
I can't comment on your particular circumstances, but my first thought would indeed be the existing incoming cable would be unsuitable.
Taking the guides from both DNO I know, the normal size for the incoming service cable is 25mm^2, and any fuse size should be 60A, 80A or 100A (one DNO has 100A as standard whilst the other has 80A) - this is for new supplies.
Therefore if you want three connections, each would have say 80A fuses meaning that the single service cable could experience 240A (or 300A or 180A - depending upon the fuse sizes) - this would be more than the capacity of the cable. (Even ignoring the looped supply rules.)
At the moment the supply would likely be 100A fuse, and then you are fusing down for each sub-customer, irrespective of the actual load, their service cable is effectively limited to 100A by the main fuses and one supply point.
The DNO cannot supply less than 60A as the obligation is 60A minimum to allow for evcp and/or solar panel.
The maximum service cable length is normally 30m, so this is the only portion that you should be responsible for if you require new supplies, their LV main is their responsibility alone.
A looped supply is no longer permitted, it is permitted to link off the single service cable to two supplies (to the SAME customer) but then the maximum total fuse limit is 120A , along with a number of other rules concerning multiple supplies into a multi occupancy building.
However, it is sometimes possible to breach individual rules providing that they get permission from the Compliance and Performance Manager within the Connections directorate, though this would be rare.
Please remember, when the DNO provides a service point, by law they are obliged to service this for its lifetime to all the legal requirements.
Even though you may say, we only need 40A and intend to keep the load well below this. In 20 years, when you have moved on, the new customer would have every right to demand their supply complies with the regulations/law, irrespective of what you may have agreed.
So no matter what the current load is (and why your electricians say the cable is big enough) it is the regulations that must be followed. Unlike the wiring regs which are kind of supported by law in a round about way, via hse and building regulations - their obligations are directly supported by law.
I should have added more Re multi-occupancy buildings.
Basically there are two systems applicable to you A1 and A2 , A1 is basically separate service cables to each meter and is where each occupant is separate (including water and gas supplies if metallic).
A2 is where you provide a metering room in a single building, in this case there are a couple of flavours - small and general, the general has large 95mm^2 ++ service cable, whilst the small (up to 3 or 4) has a minimum of 35mm^2
These are detailed in ENA EA G87 (attached)
All DNO have to adhere to these
so if your existing supply is 25mm^2 (or less in older installations) you could not use this for A2, if you have shared metallic water/gas you cannot use A1.
Hence you may have a number of reasons which appear contradictory - but that's likely due to the two arrangements possible.
I suspect they are stating the service cable size has to be increased to enable an A2 option.
Basically there are two systems applicable to you A1 and A2 , A1 is basically separate service cables to each meter and is where each occupant is separate (including water and gas supplies if metallic).
A2 is where you provide a metering room in a single building, in this case there are a couple of flavours - small and general, the general has large 95mm^2 ++ service cable, whilst the small (up to 3 or 4) has a minimum of 35mm^2
These are detailed in ENA EA G87 (attached)
All DNO have to adhere to these
so if your existing supply is 25mm^2 (or less in older installations) you could not use this for A2, if you have shared metallic water/gas you cannot use A1.
Hence you may have a number of reasons which appear contradictory - but that's likely due to the two arrangements possible.
I suspect they are stating the service cable size has to be increased to enable an A2 option.
I add an extract from a typical code of practice which translates the myriad of regulations into practice below:
Separate Services Originating outside the Building (A1)
This type of arrangement is suitable where each of the Premises, eg flats, maisonettes, retail and small industrial, has separate access at ground floor level, or where first-floor Premises, eg flats, have external access via a staircase and landings and rising services can be safely accommodated external to the building. There shall be no communication between Premises and no indoor communal area.
Services shall be installed in accordance with standard "New Whole-current Metered Connections up to 60kVA."
Service terminations and meters may be accommodated in outside viewing cabinets or inside the Premises.
LV Connection to Intake Position within the Building (A2, A3)
Group Metering at the Intake Position
An example of this arrangement for a small number of Customers is illustrated in Figure A2 and for a larger numbers of Customers, Figure A3.
This type of arrangement is suitable for any number of floors and Customers.
One multi-way distribution fuseboard, with either group metering, as described here or distributed metering.
Boundary metering (for DUoS purposes) is not required. "This DNO" will install
a cut-out at the Intake Position. Up to three Customers, with an additional single-phase connection for a landlord’s service, may be connected directly to the "This DNO" cut-out connected via a 3-core 35mm2 SAC incoming service cable (Figure A2).
Where the number of Customers, or their demand exceeds that which can be
accommodated in this way, the BNO shall install a main switch (or switches) and multi-way distribution fuseboard for connection to the cut-out (Figure A3). A 200A distribution board fed via a 3-core 95mm2 SAC incoming service cable may be used to feed more than 3 customers, up to 6 customers.
The BNO shall be responsible for all equipment that is beyond the "This DNO" cut-out.
The BNO shall arrange for the fitting and connection, by the appropriate Meter Operator, of the appropriate meters to the main switches or to the multi-way distribution fuseboard.
Notes
The figures are in G87, and the bits in "..." are where I have replaced specific DNO information
Separate Services Originating outside the Building (A1)
This type of arrangement is suitable where each of the Premises, eg flats, maisonettes, retail and small industrial, has separate access at ground floor level, or where first-floor Premises, eg flats, have external access via a staircase and landings and rising services can be safely accommodated external to the building. There shall be no communication between Premises and no indoor communal area.
Services shall be installed in accordance with standard "New Whole-current Metered Connections up to 60kVA."
Service terminations and meters may be accommodated in outside viewing cabinets or inside the Premises.
LV Connection to Intake Position within the Building (A2, A3)
Group Metering at the Intake Position
An example of this arrangement for a small number of Customers is illustrated in Figure A2 and for a larger numbers of Customers, Figure A3.
This type of arrangement is suitable for any number of floors and Customers.
One multi-way distribution fuseboard, with either group metering, as described here or distributed metering.
Boundary metering (for DUoS purposes) is not required. "This DNO" will install
a cut-out at the Intake Position. Up to three Customers, with an additional single-phase connection for a landlord’s service, may be connected directly to the "This DNO" cut-out connected via a 3-core 35mm2 SAC incoming service cable (Figure A2).
Where the number of Customers, or their demand exceeds that which can be
accommodated in this way, the BNO shall install a main switch (or switches) and multi-way distribution fuseboard for connection to the cut-out (Figure A3). A 200A distribution board fed via a 3-core 95mm2 SAC incoming service cable may be used to feed more than 3 customers, up to 6 customers.
The BNO shall be responsible for all equipment that is beyond the "This DNO" cut-out.
The BNO shall arrange for the fitting and connection, by the appropriate Meter Operator, of the appropriate meters to the main switches or to the multi-way distribution fuseboard.
Notes
The figures are in G87, and the bits in "..." are where I have replaced specific DNO information
Last edited:
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