Hello. We have a 1600A ATS which is being fed form a generator on the emergency side and a substation of the normal side. The generator is a 900KW gen, with a 1600AF/1200AT circuit breaker and same is breaker sizing on the normal side (Substation side). We are in process of replacing the generator. The existing cables are 4 sets of 500MCM (1520A). The contractor is suggesting the new cables need to be re-sized to 600MCM. Is there a NEC code reference to this, that they should be sized to FLA of 1600A?
Wire sizing
- Thread starter adi2873
- Start date
- Status
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
The conductors maybe as oversized as you like. You protect them at their rating. 240.4(C) in your case, says that your 1200A breaker can be matched with any conductors with ampacity 1200A or larger.
Got it. Is there a reference to your Comment in NEC?
- Location
- Illinois
- Occupation
- retired electrician
There is no specific language in the code. Assuming that breaker uses a "rating plug" to set the current, the rating of the plug is the rating of the breaker. The frame is the maximum size rating that can be used.
If this is an adjustable trip breaker, then you need to look to the requirements of 240.6(C).
- Location
- New Jersey
- Occupation
- Journeyman Electrician
The frame versus trip is similar to a fused switch. You can have a 1600 amp switch with 1200 amp fuses and 1200 amp conductors.
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