- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Two somewhat odd questions. I will have two transformers operating in parallel. Each secondary will be protected by a 2000 amp fuse and a network protector. The calculated neutral current is well below the ungrounded conductor?s current, so I won?t need the neutral to have the same ampacity as the ungrounded. The engineer designing this system wants to use the following:
? 5 conductors for phase A, each 750 MCM copper.
? 5 conductors for phase B, each 750 MCM copper.
? 5 conductors for phase C, each 750 MCM copper.
? 3 conductors for the neutral, each 750 MCM copper.
All of these will be single-conductors, and all will be routed within the same enclosure that connects the network protectors to the downstream busway. The distance within the enclosure is under 2 feet, so I don?t expect derating issues. The conductors are not part of a cable system, and I would not call the connecting enclosure a ?raceway.? So I don?t think 310.4(C) comes into play.
The two transformers are not identical, in that one is 500 KVA and the other is 1000 KVA. This is an existing situation; we are not creating or changing that disparity. We are replacing a PCB-liquid filled transformer, and the specifications for the new transformer will require matching impedance with its future roommate.
Question 1: Is it code compliant to have a different number of conductors for the phase conductors and the neutral conductors.
Question 2: Is there a code requirement that would be violated by having differently rated transformers?
? 5 conductors for phase A, each 750 MCM copper.
? 5 conductors for phase B, each 750 MCM copper.
? 5 conductors for phase C, each 750 MCM copper.
? 3 conductors for the neutral, each 750 MCM copper.
All of these will be single-conductors, and all will be routed within the same enclosure that connects the network protectors to the downstream busway. The distance within the enclosure is under 2 feet, so I don?t expect derating issues. The conductors are not part of a cable system, and I would not call the connecting enclosure a ?raceway.? So I don?t think 310.4(C) comes into play.
The two transformers are not identical, in that one is 500 KVA and the other is 1000 KVA. This is an existing situation; we are not creating or changing that disparity. We are replacing a PCB-liquid filled transformer, and the specifications for the new transformer will require matching impedance with its future roommate.
Question 1: Is it code compliant to have a different number of conductors for the phase conductors and the neutral conductors.
Question 2: Is there a code requirement that would be violated by having differently rated transformers?