4000A Main Distribution Panel Minimum Wire Size Line Side

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Zyb

Zyb

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I need to interconnect to a line side of 208Y/120V. 3 phase, 4W 4000A Main Distribution Panel. what's the minimum wire I can use? Thank you
I have 250MCM CU wire (188A PV Solar).

is 500MCM as my ground correct using NEC 250.122?
how about for current carrying conductor?

1668530752797.png
 
texie said:
Before answering your question I'm wondering how you are going to tap those services conductors. Do you realize you have to tap all of them together for each phase and how much room you will need given there are likely about 12 sets for a service this large?
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I am thinking he plans on hitting the bus-bar with an additional lug?

UNGROUNDED CONDUCTOR SIZE(s):

If you figure the 25 foot tap rule (really applies AFTER the Main?) then you use 1/3 the total amp of the feeder(s) . . . 1/3 = 1333 Amps . . . so that would be something like (4 sets) 500 or 600 MCM(s).

If you figure the 10 foot tap rule (really applies AFTER the Main -- and was originally to power control circuits) . . . 1/10 = 400 Amps so that would be something like (1 set) 500 MCM.

If you tap BEFORE the Main -- then it is an additional Service Disconnect -- so the PV Feeder matches the stated: 250MCM CU wire (188A PV Solar) (is that correct?).

GROUNDING CONDUCTOR SIZES(s):

If tapped BEFORE the Main, then Service Grounding is set by the PV Disconnect Amps -- per Table 250.66

If tapped AFTER the Main (now an Equipment Ground) is set by Circuit Breaker or Fuse size -- per Table 250.122.

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Those are my quickie numbers. You mileage may vary to match site conditions and requirements and AHJ.
 
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Agree on the line side the phase conductors would be sized per your solar (250)
The "Grounnd" IMO, would be a bonding jumper based on the 250 so a #2
 
Phil Timmons said:
I am thinking he plans on hitting the bus-bar with an additional lug?

UNGROUNDED CONDUCTOR SIZE(s):

If you figure the 25 foot tap rule (really applies AFTER the Main?) then you use 1/3 the total amp of the feeder(s) . . . 1/3 = 1333 Amps . . . so that would be something like (4 sets) 500 or 600 MCM(s).

If you figure the 10 foot tap rule (really applies AFTER the Main -- and was originally to power control circuits) . . . 1/10 = 400 Amps so that would be something like (1 set) 500 MCM.

If you tap BEFORE the Main -- then it is an additional Service Disconnect -- so the PV Feeder matches the stated: 250MCM CU wire (188A PV Solar) (is that correct?).

GROUNDING CONDUCTOR SIZES(s):

If tapped BEFORE the Main, then Service Grounding is set by the PV Disconnect Amps -- per Table 250.66

If tapped AFTER the Main (now an Equipment Ground) is set by Circuit Breaker or Fuse size -- per Table 250.122.

------------

Those are my quickie numbers. You mileage may vary to match site conditions and requirements and AHJ.
Click to expand...
Those tap rules are for tapping feeders, not service conductors.
 
ggunn said:
Those tap rules are for tapping feeders, not service conductors.
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Agree.

That is why I was breaking it out to "BEFORE" the Main (Service Conductors) and "AFTER" the Main(s)?

I am not seeing ANY Existing Main Service Disconnect(s) in his sketch, are you?

The "Grid" Label has no well-defined meaning in this regard -- but I agree it would "usually" (whatever that may mean) and therefore imply the Existing Main Service Disconnect(s) are in the Switchgear -- but then it may also have multiple Main Breakers (or Fuses) and create additional issues, there.

Such are half-baked, preliminary 1-Lines. ;P
 
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Phil Timmons said:
Agree.

That is why I was breaking it out to "BEFORE" the Main (Service Conductors) and "AFTER" the Main(s)?

I am not seeing ANY Existing Main Service Disconnect(s) in his sketch, are you?

The "Grid" Label has no well-defined meaning in this regard -- but I agree it would "usually" (whatever that may mean) and therefore imply the Existing Main Service Disconnect(s) are in the Switchgear -- but then it may also have multiple Main Breakers (or Fuses) and create additional issues, there.

Such are half-baked, preliminary 1-Lines. ;P
Click to expand...
Yeah, there wasn't much detail there, but he did say it was to be a line side interconnection.
 
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texie said:
Before answering your question I'm wondering how you are going to tap those services conductors. Do you realize you have to tap all of them together for each phase and how much room you will need given there are likely about 12 sets for a service this large?
Click to expand...
It's actually on the bus, this is just how we show it on our drawing
 
Zyb said:
It's actually on the bus, this is just how we show it on our drawing
Click to expand...
So the Existing Main Service Disconnect(s) are in or are the 4000 Amp Equipment?

If so, two more things to consider -- (you might get these waived by AHJ, or AHJ may not catch these)

1. Grouping of Disconnects (if the 4000 Amp Equipment is indoors, and your new Solar PV Service Disconnect is outdoors)
2. Total Number of Service Disconnects -- standard total limit is 6, for both the indoors and outdoors.
 
Phil Timmons said:
So the Existing Main Service Disconnect(s) are in or are the 4000 Amp Equipment?

If so, two more things to consider -- (you might get these waived by AHJ, or AHJ may not catch these)

1. Grouping of Disconnects (if the 4000 Amp Equipment is indoors, and your new Solar PV Service Disconnect is outdoors)
2. Total Number of Service Disconnects -- standard total limit is 6, for both the indoors and outdoors.
Click to expand...
A PV disco doesn't count toward the six handle rule.

Breaking 6 handle Rule?

Would adding a line side tap at the SES for a PV disconnect to an SES that already has 6 disconnects violate the 6 handle rule? We are under the 2014 NEC.
forums.mikeholt.com
 
ggunn said:
A PV disco doesn't count toward the six handle rule.

Breaking 6 handle Rule?

Would adding a line side tap at the SES for a PV disconnect to an SES that already has 6 disconnects violate the 6 handle rule? We are under the 2014 NEC.
forums.mikeholt.com
Click to expand...
Is that true? Or something that varies by AHJ?

Are we both talking about a BEFORE the Main(s) Service Disconnect tap?
 
Phil Timmons said:
Is that true? Or something that varies by AHJ?

Are we both talking about a BEFORE the Main(s) Service Disconnect tap?
Click to expand...
The AHJ could overrule it, I guess, but it's legit by code, and yes, we are talking about between the utility meter and the MSD.
 
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