I have posted a piece here which is also on the TT topic, but is more general and I think a new thread would be better. Your voice is heard. See below.
If I understand what David is saying, the manufacturers require that the sum of the ratings of the MCBs after each RCD is no greater than the rating of the RCD. So why is it that the sum of the ratings of the RCDs may exceed that of the main switch? (In which case, the sum of the rating of the RCDs may also do so.)
It is also counter to 314.1. Starting from scratch, in let's say a 3-storey house, I might want one circuit for the smoke alarms and three for the lighting (one per floor). One would suffice, but with no difference in load, we have 1 x 6 A or 4 x 6 A MCBs. Similarly with 4 socket circuits (one for each floor with a separate one for the kitchen) we have 4 x 32 A, but it would be bonkers to suggest that this means that the load would ever be 128 A, especially in a modern well-insulated home.
I really must upgrade my own CU: after nearly 40 years of use, it's a wonder that it has been able to cope with 300-odd A of MCBs. ?
If I understand what David is saying, the manufacturers require that the sum of the ratings of the MCBs after each RCD is no greater than the rating of the RCD. So why is it that the sum of the ratings of the RCDs may exceed that of the main switch? (In which case, the sum of the rating of the RCDs may also do so.)
It is also counter to 314.1. Starting from scratch, in let's say a 3-storey house, I might want one circuit for the smoke alarms and three for the lighting (one per floor). One would suffice, but with no difference in load, we have 1 x 6 A or 4 x 6 A MCBs. Similarly with 4 socket circuits (one for each floor with a separate one for the kitchen) we have 4 x 32 A, but it would be bonkers to suggest that this means that the load would ever be 128 A, especially in a modern well-insulated home.
I really must upgrade my own CU: after nearly 40 years of use, it's a wonder that it has been able to cope with 300-odd A of MCBs. ?
