Can you have a cutout for each conductor of a parallel feed?

[Electrical Hazard]

I have a customer who has a 400A parallel feed (25kV). He has two sets of 200A cutouts (a total of 6) that feed the main inside the building. I don't think this is truly a parallel feed anymore. I don't really agree with this practice but need a code reference that proves or disproves this.

 

[walkerj]

Could this possibly be a Main-Tie-Main?

 

[Dennis Alwon]

Here is what the NEC says about parallel. I cannot tell from your description if this is what you have.

310.4 Conductors in Parallel.
(A) General. Aluminum, copper-clad aluminum, or copper conductors of size 1/0 AWG and larger, comprising each phase, polarity, neutral, or grounded circuit conductor shall be permitted to be connected in parallel (electrically joined at both ends).

 

[Electrical Hazard]

Its not a Main-Tie-Main. All Cutouts are closed and they land directly on the line side of Main. They are trying to have a parallel feed but it is only connected at the one end. If the cutouts are closed they electrical connected at one end but if one of the C phase cutouts are open they aren't and it is being back fed at the bottom from the other C phase.

 

[weressl]

I have a customer who has a 400A parallel feed (25kV). He has two sets of 200A cutouts (a total of 6) that feed the main inside the building. I don't think this is truly a parallel feed anymore. I don't really agree with this practice but need a code reference that proves or disproves this.

If the cutout is in a magnetizable sheetmetal plate/enclosure each set of the three phase conductors should enter through a single opening, eg. two openings for each three conductors comprising A-B-C phases. This is to avoid the heating of the plate/enclosure of the inductive heat generated by the unbalanced currents. This is not an NEC requirement AFAIK.

In some cases where single conductor entry is required, one may install a non-metallic, aluminum or non-magnetizable stainless entry plate.

 

[jim dungar]

Its not a Main-Tie-Main. All Cutouts are closed and they land directly on the line side of Main. They are trying to have a parallel feed but it is only connected at the one end. If the cutouts are closed they electrical connected at one end but if one of the C phase cutouts are open they aren't and it is being back fed at the bottom from the other C phase.

If the fuse line sides are on the same bus (the cutouts don't count) and the load side of the conductors are on the same bus, then the fuses are in parallel and therefore are against code, unless they are part of a listed assembly.

 

[jeremysterling]

Here is what the NEC says about parallel. I cannot tell from your description if this is what you have.

I agree with Dennis. The cutout is probably not #1/0 AWG.

 

[weressl]

If the cutout is in a magnetizable sheetmetal plate/enclosure each set of the three phase conductors should enter through a single opening, eg. two openings for each three conductors comprising A-B-C phases. This is to avoid the heating of the plate/enclosure of the inductive heat generated by the unbalanced currents. This is not an NEC requirement AFAIK.

In some cases where single conductor entry is required, one may install a non-metallic, aluminum or non-magnetizable stainless entry plate.

Duh, cutout and knockout......I can never get used to the Utility terms...

 

[masterinbama]

If I get what you are saying, you have 2 conductors per phase and each conductor is fused with a 200 amp cutout.

 

[Electrical Hazard]

Yes, there is 2 conductors per phase and each conductor has a 200A Fused Cutout feeding a 400Amp Main.

 

[pete m.]

Perhaps 490.21(B) may have some bearing on your question.

Pete

 

[dbuckley]

Dennis quoted it and added a clarification "electrically joined at both ends "; you don't have both ends of both conductors go to the same place, thus in my opinion, so they are not parallel conductors by the NEC definition. Each conductor goes to its own fuse.

The arrangement you have is safe, as each conductor is protected by its own fuse, but I have no idea if this is code compliant or not. Jim suggests it is not, and I'm inclined to believe him.

This sort of arrangement is used in other jurisdictions, as you can do this to build a safe high availability path (each conductor being adequate for the full load), whilst having the ability to isolate part of it so one can work on it without it being hot. And also needing two breakers or fuses in parallel to both open before the circuit is isolated, making breaker failure not an availability issue. Makes the coordination and fault currents entertaining, if it ever does go wrong, though...