200A 3 ph 4 wi fuse protected safety switch

[mikehughes8]

Am I allowed to pull 1 phase from a 200A 3 phase safety switch to feed a single phase 125A panel. I realize this is a strange question but I am trying to spare everyone the lenghty history on this one. If I can't please refer me to the section of the code that says so.

Thanks in advance

 

[ron]

Without more detail, I would say that generally it is okay.

 

[charlie b]

Help me understand the question. You have an existing 200 amp fused switch, serving (I presume) a 200 amp panel somewhere. You want to connect a wire to one load terminal and a wire to the neutral, and with these two wires serve a new, separate, 125 amp panel. Is that right?

I think that if you size the wire to the 125 amp panel such that a 200 amp fuse protects it, or can otherwise apply one of the tap rules to allow the use of a smaller wire, and if you can show by calculation or other means that the combined load is not beyond the ampacity of the feeder to the safety switch, and if the neutral wire in that feeder is ?full sized? (i.e., so that the imbalance created by adding load to one phase will not exceed the ampacity of that neutral wire), then this should be allowable.

But why not provide a 125 amp fused disconnect next to the existing 200 amp fused disconnect, and make your connection on the line side of the 200 amp device? That makes the two downstream panels a bit more independent.

 

[SEO]

Is the 200 amp switch feeding anything else? If not as long as you provide conductors and overcurrent protection sized for your 125Amp panel you could use the three phase panel for single phase. Just leave one fuse out. If it is a delta system omit your power phase and if it is a wye system make sure that you install a full size neutral. and omit one fuse. If the 200amp switch is feeding something else I'll need more information.

 

[mikehughes8]

I suppose a little more information is needed.
There are several 200Amp safety switches. They are usually connected to military vehicles at a loading dock via a a pigtail and a mil spec connector. However, the customer doesn't use all (26) of these switches and would like to use the spares to connect into (3) double wide trailers fabricated with 125Amp single phase panels. Customer wants to complete project at a minimal expense using existing infrastructure where ever possible. I was exploring a couple of options.
1) I could connect the 3 phase 4 wire switch into a 200A 3 phase 4 wire panel. This panel would contain (3) 125A breakers each feeding a its own 125Amp panel on the double wide buildings.
2) In an effort to avoid installing a panel I could tap off of 1 terminal on 3 seperate switches and feed each new double wide panel independently. I would use just one switch except for the fact I don't have a convienient way of connecting (3) neutrals.
I can accomplish phase balance by using A,B,C phase respectively on switches 1,2,3

In a perfect world I would simply run a new feeder from the 750KVA utility transformer to a new disconnect to accomplish this. But that is not going to happen.
It's a retarded setup I admit yet I may not have a choice. I just want to make sure I do this as safely as possible.

 

[jim dungar]

2) In an effort to avoid installing a panel I could tap off of 1 terminal on 3 seperate switches and feed each new double wide panel independently. I would use just one switch except for the fact I don't have a convienient way of connecting (3) neutrals.
I can accomplish phase balance by using A,B,C phase respectively on switches 1,2,3

Do you want (3) 3-wire loads
AB + N to load 1
BC + N to load 2
CA + N to load 3

Or (3) 2-wire loads
A + N to load 1
B + N to load 2
C + N to load 3

 

[mikehughes8]

I am looking for 2-wire loads
A-N
B-N
C-N
Lighting and receptacles only!

 

[mikehughes8]

I am looking for 2-wire loads
A-N
B-N
C-N
Lighting and receptacles only!

Sorry I wasnt thinking (3 wire connection just like in a home)
AB-N
BC-N
CA-N

 

[jim dungar]

Sorry I wasnt thinking (3 wire connection just like in a home)
AB-N
BC-N
CA-N

You want (3) different MWBC fed from a single three pole device? Off the top of my head I don't see why not.

 

[LarryFine]

1) I could connect the 3 phase 4 wire switch into a 200A 3 phase 4 wire panel. This panel would contain (3) 125A breakers each feeding a its own 125Amp panel on the double wide buildings.

This option gets my vote.

 

[Smart $]

...
2) In an effort to avoid installing a panel I could tap off of 1 terminal on 3 seperate switches and feed each new double wide panel independently. I would use just one switch except for the fact I don't have a convienient way of connecting (3) neutrals.
I can accomplish phase balance by using A,B,C phase respectively on switches 1,2,3
...

If you have multiple 3? 4W disconnect switches available for use, just use two poles and the neutral from each of three in staggered fashion—switch1:ABN, switch2:BCN, and switch3:ACN. Fuse at 125 or above and size [3-wire w/G] feeders at an ampacity equal to or greater than the fuse rating.

If you only want to use one switch, fuse at 200A, run 200A [3-wire w/G] feeder, and tap off within the rules to each trailer.

You didn't mention distance, so it remains uncertain which way is the least expensive.

Note for any method, a disconnect switch within sight of and not more than 30' from the trailer served is required. Additionally, it must be external but not attached to the exterior.