Grounded Conductor

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Cody K

Senior Member
Location
Texas
I have a question regarding service disconnecting means, grounded conductor, grounding conductor, and bonding.

An industrial facility (480Y/277) we are installing consists of a 2000A MCB at the utility poles... the feed goes about 50ft into an 2000A MCC building with a 2000A MCB at the entrance (which is also rated for service disconnect although not used for such). We have a 480/277v lighting panel inside that we were planning on using for lighting (at 277), other than that all the loads are line to line. The problem is that there is only one bar inside MCC for grounding so IMO we would bond there and run one grounded conductor along with the other three wires back to the service disconnecting means and up the pole. Also at this point the engineer for the company we bought this equipment from said this MCC was not designed for 4wire and that the 480/277 lighting panel was installed by mistake. So now I am wondering if bonding in the MCC would be wrong and to completely scrap any thoughts of line to neutral loads, also the MCC is not the service disconnecting means if that matters.

Do you guys have some ideas? Thanks
 
Cody, Your neutral/ground MBJ will be done at the service disconnect. It

sounds like the MCC is 3 wire with EGC, no neutral. For your lighting you could

use a 3 phase transformer and generate a SDS for 120/208Y !!
 
Thanks, I am going to talk to the supplier engineer today and that is exactly what he had said before. I'm not real familiar with MCC types, I would have never thought that some would not come with a nuetral bar. Thanks again for you input.
 
Cody, can you post a sketch of what you have? With the MCC downstream of the main disconnect, and serving only line to line loads, you really don't need the neutral there anyway.
 
crossman said:
Cody, can you post a sketch of what you have? With the MCC downstream of the main disconnect, and serving only line to line loads, you really don't need the neutral there anyway.
Click to expand...

You are correct, however if we were to connect the lighting panel which is 277 then we would need the neutral conductor. I think we will run our lights on some other voltage that is available thru transformers. Thanks
 
Oh... so you were going to connect the lighting panel out of the MCC? I was thinking the lighting panel and MCC were both fed from the main disconnect via taps.
 
crossman said:
Oh... so you were going to connect the lighting panel out of the MCC? I was thinking the lighting panel and MCC were both fed from the main disconnect via taps.
Click to expand...

We have several options in the MCC that is fed 3 phase 480Y/277. The options are:

--480/277 three phase lighting panel fed directly off buss (100 panel)
--208/120 three phase fed from an inside transformer (15kva)
--120/240 single phase transformer fed from an inside transformer (5kva)

The cans were setup to conveniently use the 277 panel with the lighting contactor but as luck has it the MCC does not have a neutral bus bar. So we will make plans on using another voltage, it will just require some extra work. I wanted to make sure that the MCC was in fact not setup for such before we planned alternative measures for lighting. I never would have thought an MCC would come without a neutral.
 
Would it be possible to bring the grounded conductor in from the service disconnect and just splice (or not) inside the MCC and go directly to the 277/480 lighting panel? I don't know of any code requirement that would mandate that the grounded conductor having to terminate in the MCC.

Pete
 
pete m. said:
Would it be possible to bring the grounded conductor in from the service disconnect and just splice (or not) inside the MCC and go directly to the 277/480 lighting panel? I don't know of any code requirement that would mandate that the grounded conductor having to terminate in the MCC.

Pete
Click to expand...

I guess we could. Supposing we would still bond neutral and ground at the service disconnect.

The only problem with that is that we would have to run a ground and a neutral conductor (5 wires) back to the service.
 
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