I have a 400A fused disconnect on the exterior feeding a 200A enclosed brkr just inside on the opposite side of the wall. I would like to tap onto the lugs of this service disconnect to feed a 200A MCB panel on the interior (within 10ft). Is this an allowable application of the tap rule under NEC 240.21?
Tap Rule
- Thread starter buccs407
- Start date
- Status
- Location
- New Jersey
- Occupation
- Journeyman Electrician
What side of the 400 amp disconnect are you tapping?
- Location
- Illinois
- Occupation
- retired electrician
It would appear that you would have 3 service disconnects that are not grouped as required by 230.72(A). If I understand your installation correctly, it is already in violation of this section.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
I believe that the 400 amp disconnect is the service disconnect and the taps are on the load side. Would that make the other two feeders, feeder taps?
- Location
- Illinois
- Occupation
- retired electrician
You're correct, I read load as line when I read the post.
Yes, the exterior 400A disconnect is the service disconnect for the building. If this is allowable, Would each set of tap conductors be able to be sized for 200A, or should they be sized for 400A? I know the NEC states that the ampacity of the tap conductors must not be less than the combined calculated loads on the circuits to be supplied.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Will you installation fall under the 10' tap rule? If so, your tap condcutors can be from 40 to 399 amps. If they're 400 amps they're no longer tap conductors.
Volta
Senior Member
- Location
- Columbus, Ohio
No, you're right, they do not need to be adjacent, on in sight from.
The EGC has to be no smaller than a #3, as the circuit is protected at 400 amps.
Volta
Senior Member
- Location
- Columbus, Ohio
Yes, 250.122(G). They both should be #3.
2" will still be ok for everything, unless 3 phase with full neutral in Schedule 80 PVC, then 2-1/2.
2" will still be ok for everything, unless 3 phase with full neutral in Schedule 80 PVC, then 2-1/2.
Volta
Senior Member
- Location
- Columbus, Ohio
Sure thing!
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Since your using tap conductors with an ampacity 1/3 or larger than the 400 amps you could use the 25' tap rule even for taps that enter the building. If the tap conductors are on the outside of the building then their length is unlimited.
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