Parallel or not???

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mollydodger

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I have a concern regarding an installation I am being told to do. This is in a data center and the system is 120/208 volts

1. There are two separate sources of supply, one 400 amp breaker located on one cabinet and one in another cabinet.
2. I am supposed to run two sets of 4/0 copper from each 400 amp breaker to a distribution cabinet which will supply branch circuits.
3. The distribution cabinet has FOUR DISTINCT and separate sections A,B,C and D

I believe this is a violation of NEC as the sets of conductors originate at a single source (paralleled) and terminate in diferent locations at the distribution cabinet. Am I correct? Any comments on potential issues and or NEC violations are appreciated!!!!

Thanks in advance!!!!!!!!!!!
 
You have not indicated what the 4/0 on the load end are terminated to. For example main lug, main breaker or something else.

Since you indicate that the 4/0 conductors terminate in four separate loads I would not consider the two sets of 4/0 originating from a 400 amp breaker a ? (paralleled)? feed.

I would look at this being a 4/0 tap from a 400 amp breaker
 
termination at distribution cabinet

termination at distribution cabinet

david said:
You have not indicated what the 4/0 on the load end are terminated to. For example main lug, main breaker or something else.

Since you indicate that the 4/0 conductors terminate in four separate loads I would not consider the two sets of 4/0 originating from a 400 amp breaker a ? (paralleled)? feed.

I would look at this being a 4/0 tap from a 400 amp breaker
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I was mistaken on my reply to you. The conductors are to terminate at four separate breakers which supply the four separate sections of the distribution cabinet.
 
mollydodger said:
I was mistaken on my reply to you. The conductors are to terminate at four separate breakers which supply the four separate sections of the distribution cabinet.
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The 4/0 conductors would still be a tap from the 400 amp supply breaker, the load end breaker would provide the single overcurrent device for the 4/0 tap.
 
david said:
The 4/0 conductors would still be a tap from the 400 amp supply breaker, the load end breaker would provide the single overcurrent device for the 4/0 tap.
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Did the OP state that the run was less than 25 feet? Otherwise what tap rule would allow it?
 
Strathead said:
Did the OP state that the run was less than 25 feet? Otherwise what tap rule would allow it?
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he didn't state one way or the other.

mollydodger said:
I have a concern regarding an installation I am being told to do. This is in a data center and the system is 120/208 volts

1. There are two separate sources of supply, one 400 amp breaker located on one cabinet and one in another cabinet.
2. I am supposed to run two sets of 4/0 copper from each 400 amp breaker to a distribution cabinet which will supply branch circuits.
3. The distribution cabinet has FOUR DISTINCT and separate sections A,B,C and D

I believe this is a violation of NEC as the sets of conductors originate at a single source (paralleled) and terminate in diferent locations at the distribution cabinet. Am I correct? Any comments on potential issues and or NEC violations are appreciated!!!!

Thanks in advance!!!!!!!!!!!
Click to expand...

he also didn't say that the conductors terminated at an OCPD as is also required for tap conductors.
 
mollydodger said:
I believe this is a violation of NEC as the sets of conductors originate at a single source (paralleled) and terminate in diferent locations at the distribution cabinet.
Click to expand...
It is not a parallel condition unless the conductors are connected to each other at both ends. If they originate from a single source and terminate at different locations, they are not in parallel. Therefore, you would be using a 400 amp breaker to provide overcurrent protection for conductors that are only rated for 230 amps. That is a violation, unless you can meet one of the tap rules. It appears that this would not meet any tap rule.

I agree with Bob, in that if you connect two of the 4/0 feeders to each other both at the point of origin (the 400 amp feeder breaker) and the point of termination (for example at the main breaker for distribution cabinet A), then run a parallel set of 4/0 conductors over to the main breaker for distribution cabinet B, and do the same for cabinets C and D, you will have a compliant installation.

 
if the load side breakers are close enough he could even run the paralleled 4/0 cables to a junction box and tap off a single 4/0 to each load breaker using the tap rules.
 
Being in one distribution cabinet - is this a condition of mutiple circuits to a single piece of equipment? simontaneous disconnecting
 
mollydodger said:
I have a concern regarding an installation I am being told to do. This is in a data center and the system is 120/208 volts

1. There are two separate sources of supply, one 400 amp breaker located on one cabinet and one in another cabinet.
2. I am supposed to run two sets of 4/0 copper from each 400 amp breaker to a distribution cabinet which will supply branch circuits.
3. The distribution cabinet has FOUR DISTINCT and separate sections A,B,C and D

I believe this is a violation of NEC as the sets of conductors originate at a single source (paralleled) and terminate in diferent locations at the distribution cabinet. Am I correct? Any comments on potential issues and or NEC violations are appreciated!!!!

Thanks in advance!!!!!!!!!!!
Click to expand...

I'm still trying to figure out how your running from (2) separate sources of supply to a "Common Distribution" cabinet without going through some type of Transfer switch.
Not sure we're getting the complete picture.

JAP>
 
Strathead said:
Did the OP state that the run was less than 25 feet? Otherwise what tap rule would allow it?
Click to expand...

It could be allowed if most or all of the tap conductor length was outside the building, FWIW.
That includes sufficiently concrete encased to be categorized as outside the building.
 
petersonra said:
IMO, not code compliant then.

HOWEVER, if he were to parallel the (2) 4/0 cables to BOTH downstream breakers it would be OK.
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If the OP took care to size boxes or gutters correctly one way would be to get some 4 hole polaris lugs, two 4/0's in, one out to each 200 amp breaker. In that case I would even suggest that they go down to 3/0. If the 200 amp is what they were anyway.
 
GoldDigger said:
It could be allowed if most or all of the tap conductor length was outside the building, FWIW.
That includes sufficiently concrete encased to be categorized as outside the building.
Click to expand...

The tap conductors would have to originate outside of the building to use 240.21(B)(5).
 
jap said:
I'm still trying to figure out how your running from (2) separate sources of supply to a "Common Distribution" cabinet without going through some type of Transfer switch.
Not sure we're getting the complete picture.

JAP>
Click to expand...

Two sources are supplying four cabinet sections, each section with it's own main circuit breaker. I don't think any transfer equipment would be required.
 
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