As Motability pay for the EV charger, the extra cost from Ohme may still be much less than paying for my own EV Charger and installation. The second CU arrangement is Tails > Type A RCD (100/30-A 100 Amp Double Pole 30mA 10kA) > SPD followed by the individual circuit breakers. It also has 4 slots available. So may have been ideal if the 25mm tails had been fitted
However, as you note, what Ohme say and what the electrician say’s when they’re on site are two different things ! I wont say anymore about the electrician and the 16mm tails except to say ‘they’ no longer benefit from any form of accreditation. Re the HB, the block /insulation was found to be at fault between the two poles according to the report from the fire investigators. We were watching TV when we heard the cracking and the power dipped in the street. Within 10 minutes their house was ablaze.
However, as you note, what Ohme say and what the electrician say’s when they’re on site are two different things ! I wont say anymore about the electrician and the 16mm tails except to say ‘they’ no longer benefit from any form of accreditation. Re the HB, the block /insulation was found to be at fault between the two poles according to the report from the fire investigators. We were watching TV when we heard the cracking and the power dipped in the street. Within 10 minutes their house was ablaze.Your second CU, I take is for the heatpump -Do you know if your heatpump is inverter driven and what MCB A supplies the heatpump?
[A downstream protective device may protect a conductor against overload, but it can’t protect it against faults, for that you’re reliant upon whatever is upstream, which in this case is the DNO’s fuse. Therefore in theory it’s just a matter of calculating based on the fault current, characteristics of the protective device and the adiabatic behaviour of the conductor.]
Another approach is not have fault protection, BS 7671 only allows that in very specific circumstances – conductors less than 3m in length, installed in such a manner to reduce the risks of faults to a minimum and reduce the the fire risk or danger to a person. The get out is only for protecting the conductors against fault currents , not protecting people against shock as a result of a fault, so likely care is still needed with metallic containment/enclosures seen on modern 18th edition CU’s.
The other issue is, the DNO’s fuse is really outside of the scope of BS 7671 and the DNOs tend to like to keep their options open for future purposes. Meaning an installation that’s supplied by a 60A cut-out fuse today might be supplied by something else in the future (80A or 100A). The DNO won’t want to start, or is it in their scope to start having to re evaluate the designs of consumer’s installations every time they upgrade a fuse. Hence the reason, you commonly see DNOs recommend the likes of maximum (with the exception of an isolator) of 3m of 25mm² tails on a 100A fuse or 16mm² on a 60A fuse and will refuse to connect/upgrade if smaller tails are found.]
It doen’t matter what you understand of that rant, but 100A cut-out > 16mm tails > 100A RCD, does not afford protection and question the use of a Type A RCD, if your heatpump is inverter driven.
You won’t get any logical sense out of Ohme customer service, they are just office staff.