Grounding a mobile sound truck

[BlakeAB]

A friend wants to build a mobile sound booth and stage for musical productions and wants to have the option of either using a single phase 120/240 50 amp four wire plug or a single phase 120/240 50 amp four wire generator mounted on the truck. As I see it, the 4 wire plug's equipment ground will be suffient but what of the generator? The one he's looking at comes as a 4-wire system. The metal of the truck will be bonded to the generator ground. Does he have to drive a ground rod at every location?

 

[LarryFine]

Article 550?

 

[iwire]

Does he have to drive a ground rod at every location?

Not if everything is cord and plug connected.

Check 250.30 (Off the top of my head)


Larry 550?

Isn't that Mobile Homes?

 

[Pierre C Belarge]

This is an interesting situation, one the AHJ could most likely help with as far as how to classify this "structure".

Ground rods in a case such as this are installed mostly as protection for Lightning.
So, I say it would come down to how the AHJ classifies this structure.

 

[iwire]

This is an interesting situation, one the AHJ could most likely help with as far as how to classify this "structure".

Ground rods in a case such as this are installed mostly as protection for Lightning.
So, I say it would come down to how the AHJ classifies this structure.

I would say only if the AHJ decides to entirely ignore 250.34(A) or (B).

250.34 Portable and Vehicle-Mounted Generators.

(A) Portable Generators. The frame of a portable generator shall not be required to be grounded and shall be permitted to serve as the grounding electrode for a system supplied by the generator under the following conditions:

(1) The generator supplies only equipment mounted on the generator, cord-and-plug-connected equipment through receptacles mounted on the generator, or both, and

(2) The non?current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame.

(B) Vehicle-Mounted Generators. The frame of a vehicle shall be permitted to serve as the grounding electrode for a system supplied by a generator located on the vehicle under the following conditions:

(1) The frame of the generator is bonded to the vehicle frame, and

(2) The generator supplies only equipment located on the vehicle or cord-and-plug-connected equipment through receptacles mounted on the vehicle, or both equipment located on the vehicle and cord-and-plug-connected equipment through receptacles mounted on the vehicle or on the generator, and

(3) The non?current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame, and
(4) The system complies with all other provisions of this article.

We had an extremely long thread about this before.

Beside the fact it is not an NEC requirement (IMO) it is also of questionable value.

Actually bonding an otherwise electrically isolated system to earth may introduce more hazards than leaving it isolated.

 

[Pierre C Belarge]

My post was not for advocating the use of a ground rod, it was just thrown out as information. I could not see how installing a ground rod would really help this installation... that is just my opinion.

P.S. if there is a lightning storm and they decide to go ahead with the event, that is their problem

 

[iwire]

My post was not for advocating the use of a ground rod, it was just thrown out as information. I could not see how installing a ground rod would really help this installation... that is just my opinion.

10-4

P.S. if there is a lightning storm and they decide to go ahead with the event, that is their problem

If lighting strikes will a rod make a bit of difference?

The lightning jumps across the sky miles hits the trailer roof but can't make the final 8" from the steel rims past the rubber tires to the dirt?

It's just hard for me to understand what the rod will do for anything.

I certainly could be wrong.