Parallel Service Conductors
- Thread starter mike12347
- Start date
- Status
- Location
- New Jersey
- Occupation
- Journeyman Electrician
You'll find differing opinions as to whether or not you can use 310.15(B)(2) for parallel service entrance conductors. One thing is for sure 2 sets of 250 KCMIL THHN copper will have an ampacity of 510 amps. (255+255)
- Location
- Massachusetts
Infinity knows your equipment is not 90 C rated and is familiar with 110.14.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
mike12347 said:
As Bob stated, almost all equipment has lugs rated for 75 degrees C. This means that the conductors must be sized for 75 degree C also. 250 KCMIL Cu THHN has a 75 degree ampacity of 255 amps. You can look at the Article Bob referenced, 110.14(C)(1)(b)(2) for more information.
kingpb
Senior Member
- Location
- SE USA as far as you can go
- Occupation
- Engineer, Registered
mike12347 said:
What is your thought on, why it would apply?
kingpb
Senior Member
- Location
- SE USA as far as you can go
- Occupation
- Engineer, Registered
mike12347 said:
Then, I think everyone would agree............
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
IMO, because it does not explicitly state that we can. The rule is a fork in the road from "the normal way" of sizing conductors, with a boatload of restrictions on it.mike12347 said:
The conductors have to serve an individual dwelling unit.
The system has to be 120/240V. 120/208 is not allowed, because it's not mentioned. They intend for it's exclusion, so they intentionally omit it.
When we start to rationalize it and say, "Well, this is practically the same as that..." we start to stray farther from what they intended. It's an exception from the rule, not the rule itself (as far as sizing conductors for equipment goes).
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