Undersized Neutral for 4000A service

[Bifer]

For a 4000A service, we only needed a 480V/3p/3w+gnd from the utility transformer but the utility service provider required the neutral wire for the C/T at the switchboard. What is the smallest neutral wire I can ran with the ground wire from the utility transformer to service entrance equipment (switchboard where the meter is located)?

(The neutral wire will only be used for the utility metering and will be bonded to the ground at the service entrance equipment).

 

[jumper]

See 250.24(C)(1) through (C)(4). 2014 NEC.

 

[infinity]

For a 4000A service, we only needed a 480V/3p/3w+gnd from the utility transformer but the utility service provider required the neutral wire for the C/T at the switchboard. What is the smallest neutral wire I can ran with the ground wire from the utility transformer to service entrance equipment (switchboard where the meter is located)?

You do not need a "ground wire" run with the service entrance conductors because every metal component on the line side of the service disconnect is bonded to the neutral. Also unless you're using an ungrounded system you must bring a neutral conductor to the service.

 

[ron]

As mentioned, from the utility owned transformer, you typically would only bring 4 conductors (3-ungrounded and 1-grounded). There is not typically a grounding conductor into the service disconnect from the utility.

The grounded conductor will serve double duty if needed

 

[Bifer]

Thank you All! Running 3 conductors + 1 grounded conductor makes sense since both the utility transformer and the service entrance equipment are already grounded. Thanks!

 

[Smart $]

You do not need a "ground wire" run with the service entrance conductors because every metal component on the line side of the service disconnect is bonded to the neutral. Also unless you're using an ungrounded system you must bring a neutral conductor to the service.

As mentioned, from the utility owned transformer, you typically would only bring 4 conductors (3-ungrounded and 1-grounded). There is not typically a grounding conductor into the service disconnect from the utility.

The grounded conductor will serve double duty if needed

Not needing a grounding conductor (aka equipment bonding jumper) assumes the service is not a high-impedance grounded neutral system (running a grounded [neutral] conductor is not required). The utility requiring a neutral conductor is a good indication it is not such a system... but it is a good idea with a 4000A serivce to verify before changing plans and or conductors. :happyyes: