Could/should a UK domestic dwelling need a 10kA breaker in the future, especially with the rise of high-power EV chargers or heat pumps, as these additions can increase potential fault currents (PSCC) beyond what a standard 6kA breaker can handle, making 10kA a safer, "future-proof" choice for new installations or upgrades, even if 6kA is often sufficient for basic setups
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I'm not sure that installing a heat pump or an EV charger can increase the PSSC - that is more a matter of supply impedance, set by substation transformer size, and then the length and choice of DNO cabling. I don't really see home generation with solar panels changing that either, or even large battery banks, being neither needed nor able to generate currents of more than a few tens of amps, and even a few hundred wouldn't touch the sides in terms of the error bars on a typical PSSC test result.
What I can imagine is that average loads increase, and that may drive domestic split or 3 phase supplies to become more common, as this is both easier in terms of the existing distribution, and quite a lot safer in terms of arc flash and PSSC per line than a single phase higher current supply to get the same total kVA.
How many times do you measure a PSSC greater than 6000A on load side of a 100A cut out ? Round here it is rare, so rare in fact I dont think I've ever seen it ! (while less than 1kA and some muttering about lights that noticeably dim when the kettle comes on, now that is quite common. Maybe I'm out in the sticks a bit. )
Realise also that so long as the cut-out fuse is a modern cartridge type of the BS88-3 or BS1361 (ii) flavour, then the energy limiting action of the company fuse already protects the 6kA breaker, and that in effect means you are good up to supplies of up to about 16kA PSSC - by which time you have to be practically camped on the transformer and or have a factory style busbar instead of a normal meter & tails.
This may be a problem in flats with a transformer on the same floor I suppose, but personally I cannot see high PSSC becoming much more of an issue than it already is.
Mike
PS
Here is a bit more on how important it is that the supply fusing between the substation and the MCB is the right energy limiting type above 6A. Example Bussman 1361 house service fuse data. A 6kA breaker on a supply with a different upstream fusing arrangement, is NOT guaranteed to survive or fail safely on supply with a PSSC above 6kA. Old cut outs with unknown or rewirable fuses may need to be changed, or augmented by a modern fuse but there are hopefully not too many left in use.
Similar shaped BS88-3 curves from Merson (page 50...) show a closer energy limiting action.
The values of I2T is the total let-through - this is what damages downstream equipment. Quoted pre-arc levels are also quite different.
TYPE RATING (A) I2T I2T LOSS(W)
BS88-3 BMF42V100 100 68000 5.8
BS1361 100KR85 100 73,500 6.1
In any case, once above 6kA PSSC at the incomer, it is very important to check the supply arrangements in terms of upstream fusing.
I'm not sure that installing a heat pump or an EV charger can increase the PSSC - that is more a matter of supply impedance, set by substation transformer size, and then the length and choice of DNO cabling. I don't really see home generation with solar panels changing that either, or even large battery banks, being neither needed nor able to generate currents of more than a few tens of amps, and even a few hundred wouldn't touch the sides in terms of the error bars on a typical PSSC test result.
What I can imagine is that average loads increase, and that may drive domestic split or 3 phase supplies to become more common, as this is both easier in terms of the existing distribution, and quite a lot safer in terms of arc flash and PSSC per line than a single phase higher current supply to get the same total kVA.
How many times do you measure a PSSC greater than 6000A on load side of a 100A cut out ? Round here it is rare, so rare in fact I dont think I've ever seen it ! (while less than 1kA and some muttering about lights that noticeably dim when the kettle comes on, now that is quite common. Maybe I'm out in the sticks a bit. )
Realise also that so long as the cut-out fuse is a modern cartridge type of the BS88-3 or BS1361 (ii) flavour, then the energy limiting action of the company fuse already protects the 6kA breaker, and that in effect means you are good up to supplies of up to about 16kA PSSC - by which time you have to be practically camped on the transformer and or have a factory style busbar instead of a normal meter & tails.
This may be a problem in flats with a transformer on the same floor I suppose, but personally I cannot see high PSSC becoming much more of an issue than it already is.
Mike
PS
Here is a bit more on how important it is that the supply fusing between the substation and the MCB is the right energy limiting type above 6A. Example Bussman 1361 house service fuse data. A 6kA breaker on a supply with a different upstream fusing arrangement, is NOT guaranteed to survive or fail safely on supply with a PSSC above 6kA. Old cut outs with unknown or rewirable fuses may need to be changed, or augmented by a modern fuse but there are hopefully not too many left in use.
Similar shaped BS88-3 curves from Merson (page 50...) show a closer energy limiting action.
The values of I2T is the total let-through - this is what damages downstream equipment. Quoted pre-arc levels are also quite different.
TYPE RATING (A) I2T I2T LOSS(W)
BS88-3 BMF42V100 100 68000 5.8
BS1361 100KR85 100 73,500 6.1
In any case, once above 6kA PSSC at the incomer, it is very important to check the supply arrangements in terms of upstream fusing.
