Panel feeder conductors on a trailer with generator

[FAZERS]

I'm having trouble understanding how to apply some of the Section 250 tables/terminology to my design. I am installing a panel on the deck of a refrigeration equipment trailer where a generator is also installed nearby. The feeder from the generator enters the panel through some LB conduit, where I am running a few branch circuits for compressors and a condenser, which are the vast majority of the load. The ground on the generator is jumped to the neutral at the generator. I am not using 277V anywhere in my design and haven't needed neutral. My questions are:

1.) Is there code requiring that I run the neutral conductor to the panel, in similar fashion to the ungrounded conductors (power distribution lugs, in my case)

2.) Are the notes in the following diagram (attached) sufficient assumptions in how I should apply the conductor sizing requirement tables?

Thanks,

 

[petersonra]

I don't believe there is any requirement to run the neutral if it is not used.

Note A does not seem to apply since your control panel is downstream of these things.

Note B would seem to apply.

Note C does not seem to apply since there should be no GEC to your control panel unless the transformer exceeds 1000 VA.

 

[FAZERS]

Hey Bob, thanks.

For Note A, I made the assumption that my ground conductor grouped with the feeder conductors (those entering the PD/C enclosure through the LB conduit where 'A' is placed) would correspond to a "System Bonding Jumper" which seems to be incorrect. Would this be sized in accordance with just 250.122 like note B?

For note C, the externally mounted transformer is currently designated as a 3kVA dry-type (3S40F). Does wiring X2 to the ground bar qualify as that "GEC" as long as I'm within adequate size? Even at 1000VA, I needed my secondary with a common reference because the compressor heaters, safety ECMs and solenoids throughout the zone this equipment is used will all use 120. (I have avoided designating this an "instrumentation transformer" for this reason as I didn't want to assume any concessions there.)

 

[petersonra]

Hey Bob, thanks.

For Note A, I made the assumption that my ground conductor grouped with the feeder conductors (those entering the PD/C enclosure through the LB conduit where 'A' is placed) would correspond to a "System Bonding Jumper" which seems to be incorrect. Would this be sized in accordance with just 250.122 like note B?

It seems to me it is a regular EGC and should be sized that way.

For note C, the externally mounted transformer is currently designated as a 3kVA dry-type (3S40F). Does wiring X2 to the ground bar qualify as that "GEC" as long as I'm within adequate size? Even at 1000VA, I needed my secondary with a common reference because the compressor heaters, safety ECMs and solenoids throughout the zone this equipment is used will all use 120. (I have avoided designating this an "instrumentation transformer" for this reason as I didn't want to assume any concessions there.)

I don't think it is an "instrumentation transformer" because I don't think that is a NEC defined term. It is an SDS and a class 1 source and if less than 1 kVA the code allows it to be grounded to the EGC w/o a GEC. If it exceeds 1 kVA you would need to bring in a GEC and connect earth to the EGC.

My guess is few people actually do so because it is a requirement that serves no real purpose.