P
Piratepete
Just done a domestic CU change. The cutout was 100 Amps (used to supply Economy 7 storage heaters but no longer). Existing tails 16sqmm. Therefore need to change to 25sqmm as normal.
But existing tails are routed out of the top of an external flush meter box up through the (uninsulated) wall cavity into the old Wylex FB which was mounted close to the ceiling other side of wall. Couldn't shift em let alone pull new ones through!
So, I've left em, and got the supplier to reduce the cutout size to 80 Amp at no cost to the customer or myself.
Unless I'm mistaken, taking all factors into account and Ref Method C the 16sqmm cables are rated at 87 Amps. If you also assume a 25 deg ambient they are good for 89.6 Amps.
In this case, could I also have just written a note in the 'Departures from BS7671' box? From a practical point of view, the original tails were never likely to get stressed!
If I'm not mistaken, this could also be a good wheeze to avoid changing the tails, which can be a costly exercise where they come directly out of the meter and an isolation switch is needed.:angel_smile:
Pete
But existing tails are routed out of the top of an external flush meter box up through the (uninsulated) wall cavity into the old Wylex FB which was mounted close to the ceiling other side of wall. Couldn't shift em let alone pull new ones through!
So, I've left em, and got the supplier to reduce the cutout size to 80 Amp at no cost to the customer or myself.
Unless I'm mistaken, taking all factors into account and Ref Method C the 16sqmm cables are rated at 87 Amps. If you also assume a 25 deg ambient they are good for 89.6 Amps.
In this case, could I also have just written a note in the 'Departures from BS7671' box? From a practical point of view, the original tails were never likely to get stressed!
If I'm not mistaken, this could also be a good wheeze to avoid changing the tails, which can be a costly exercise where they come directly out of the meter and an isolation switch is needed.:angel_smile:
Pete
