(3) Trailer w/ 60A panels on (1) 70kVA Generator

[MomentumElectric]

I'm trying to figure out how to hook-up (3) jobsite trailers to (1) 70kVA generator.


I'm pretty sure that the inspector is going to want to see (2) ground rods driven at each trailer, plus two at the generator.


I'm not sure, but I think I may need to run SE cable to a subpanel on a pole, and then run (3) mastheads out of the pole, and then (1) masthead into each of the trailers.


It seems like that's a lot of bullshit and a lot of copper to have overhead, but since the panels are 60A, it exceeds what the code allows for SOOW cord.


Even if I could run SOOW cord, could I run it on the ground from the generator?


The alternative would be to put a 50A breaker in each of the panels, and take out the 60A (see attached picture). I think this would allow me to avoid the mastheads and overhead wiring, but not the ground rods.


The codes I could find that apply to jobsite trailers are included in the first attached document "5958 Horton"

Here is the generator:

http://www.multiquip.com/multiquip/DCA70USI.htm





Thanks for any help with this.

 

[iwire]

We would avoid going overhead if at all possible.

We generally use aluminum SER run on the ground, sleeved in PVC where needed to protect it from damage.

The last two trailers I did I put ground rods at the generator but no additional ones at the trailers. What your AHJ will require is anyone's guess.

but since the panels are 60A, it exceeds what the code allows for SOOW cord.

Is this a local rule you are talking about?

We wire generators supplying 3,000 amp switch gear with rubber cords.

 

[MomentumElectric]

We would avoid going overhead if at all possible.

We generally use aluminum SER run on the ground, sleeved in PVC where needed to protect it from damage.

The last two trailers I did I put ground rods at the generator but no additional ones at the trailers. What your AHJ will require is anyone's guess.




Is this a local rule you are talking about?

We wire generators supplying 3,000 amp switch gear with rubber cords.

The code seems to say that anything over 50A used with a mobile home / trailer doesn't allow for SO cord. Here's what I found on that. I might be reading it wrong though.

550.10(I)(1) Mast Weatherhead or Raceway. Where the calculated load exceeds 50 amperes or where a permanent​

feeder is used, the supply shall be by means of either of the following:​

​

(1) One mast weatherhead installation, installed in accordance with Article 230, containing four continuous, insulated,​

color-coded feeder conductors, one of which shall be an equipment grounding conductor​

​

(2) A metal raceway or rigid nonmetallic conduit from the disconnecting means in the mobile home to the underside​

of the mobile home, with provisions for the attachment to a suitable junction box or fitting to the raceway on the​

underside of the mobile home [with or without conductors as in 550.10(I)(1)].​

​

The manufacturer shall provide written installation instructions stating the proper feeder conductor sizes for the​

raceway and the size of the junction box to be used.​

 

[Dennis Alwon]

Since the setup is temp. the authority having jurisdiction may not require the methods used in 550. I am not sure a mobile trailer would qualify for art. 550 which is for homes. Art. 590 is for temp installations

 

[Smart $]

What you have pictured does not fall under Article 550. Those fall under Article 545.

JMO.

 

[zbang]

The last two trailers I did I put ground rods at the generator but no additional ones at the trailers.

We usually have two rods at the genny and one at each trailer. It does seem like every AHJ is different on this

We also usually use 6/4 SO cable, but it's protected at 50a. Unless you need heat, that's usually enough for most job trailers.

 

[iwire]

We usually have two rods at the genny and one at each trailer. It does seem like every AHJ is different on this

We also usually use 6/4 SO cable, but it's protected at 50a. Unless you need heat, that's usually enough for most job trailers.

In this area heat is pretty much assumed, because of that most of our job trailers need 100 or 125 amp feeders.

I don't think I have ever seen rubber cord used for temp trailers.