An extract from NFPA-NEC 2014
240.8 Fuses or Circuit Breakers in Parallel.
Fuses and circuit breakers shall be permitted to be connected in parallel where they are factory assembled in parallel and listed as a unit. Individual fuses, circuit breakers, or combinations thereof shall not otherwise be connected in parallel.
I was surprised when I asked if there was a minimum value parallel OCPD’s could be used I was told “no”.
This is a 200A breaker consisting of two 100A units used in a service disconnect until recently.
The only time I’ve seen this used in the UK has been for specialist applications such as semiconductor fuses, not for bog standard protection. If you need a 3200A fuse you buy a 3200A fuse not two 1600’s.
I know RoB will step in with his 8000A ACB he had made out of two 4000A units in parallel and I can counter with 4000A units in series due to voltage and fault levels. Both are exceptions.
It just seems a weird idea to me and wondered if anyone else knew of other instances.
240.8 Fuses or Circuit Breakers in Parallel.
Fuses and circuit breakers shall be permitted to be connected in parallel where they are factory assembled in parallel and listed as a unit. Individual fuses, circuit breakers, or combinations thereof shall not otherwise be connected in parallel.
I was surprised when I asked if there was a minimum value parallel OCPD’s could be used I was told “no”.
This is a 200A breaker consisting of two 100A units used in a service disconnect until recently.
The only time I’ve seen this used in the UK has been for specialist applications such as semiconductor fuses, not for bog standard protection. If you need a 3200A fuse you buy a 3200A fuse not two 1600’s.
I know RoB will step in with his 8000A ACB he had made out of two 4000A units in parallel and I can counter with 4000A units in series due to voltage and fault levels. Both are exceptions.
It just seems a weird idea to me and wondered if anyone else knew of other instances.
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