NEC 230 - Multiple Service Entrances - Neutrals

[2manynotez]

A quick question.

Condition:
I have a very large building (5.6 acres under roof) that because of the loads (~ 5MVA) we require two separate entrances at different ends of the building. From what I see, NEW 230 allows multiple entrances under our conditions (amperage, occupancies, use, etc...)

Question:
Is is required by code to interconnect the neutrals for these two loads? I can not find where this is discussed in the NEC

Thanks in advance

 

[chris kennedy]

Likely will be via 250.50 or 250.104.

 

[iwire]

I agree with Chris but I am curious if you really have two services or two feeders.

When I have worked on large buildings the service was basically at the property line at 13.8kv and everything beyond that was a feeder.

 

[2manynotez]

I agree with Chris but I am curious if you really have two services or two feeders.

When I have worked on large buildings the service was basically at the property line at 13.8kv and everything beyond that was a feeder.

Sorry, I was a little sketchy on information. Basically the footprint of this facility is huge and we will have two padmounted transformers [Delta/Wye] at one end serving one electrical room and the same on the other end to a second electrical room.

As far as why we want two involves (for one reason) the fact that it is a sensitive mission critical military facility with millions of dollars worth of equipment inside and we need redundancy.

Frankly I do not feel there will be any need to interconnect the neutrals between the two services, or to look at it another way, between the two electrical rooms. A work mate of mine feels differently.

We are the QA/QC group and this is not really my expertise.. I do the high voltage Transmission and Distribution technical reviews but our inside electrical man is on vacation..

 

[iwire]

Frankly I do not feel there will be any need to interconnect the neutrals between the two services, or to look at it another way, between the two electrical rooms. A work mate of mine feels differently.

There is absolutely no NEC requirement to directly connect the neutrals together and to do so in would likely be a violation in the fact that each neutral would be bonded twice.

However as Chris said the neutrals will be indirectly bonded together via the grounding electrode and bonding requirements.

 

[2manynotez]

There is absolutely no NEC requirement to directly connect the neutrals together and to do so in would likely be a violation in the fact that each neutral would be bonded twice.

However as Chris said the neutrals will be indirectly bonded together via the grounding electrode and bonding requirements.

Thank you... as I thought.

Forgive me all for being somewhat sketchy in my description of my issue..

 

[David Hinton P.E.]

Thank you... as I thought.

Forgive me all for being somewhat sketchy in my description of my issue..

You will want to bond the grounding electrodes together of both services but not the neutrals. Otherwise you will get current ground loops and are bonding the neutral (grounded conductor) and EGCs twice through both panels' MBJs. The attached pic should help.