Grounding two mobile offices feed from one generator

Status
Not open for further replies.
S

strugglinsparky

Member
Location
Fort Collins, CO
I have to hook-up two mobile office trailers from one generator. The generator is a 38 KW single phase. The mobile trailers have a exterior panel, and have a 125 amp main breaker. I have been assured by the company that the big trailer draws about 80 amps with the air conditioner running. The mobile offices are expected to be in place for 3 months, but who knows.

My plan is to use 6-4 SJOOW with 4 wire Hubbell 50 amp twist lock to connect to the generator which has a overcurrent of 50 amps, and direct wire to the panels on the side of the mobile offices. It's about 30' from generator to trailer.

I believe this is a solid plan. My question starts when I start thinking about grounding and bonding. I know I should drive a ground rod at the generator, I however do not think I should drive a ground rod at the mobile office. The G.C. is demanding that I do. This is my first job with a this client and do not want to start off with friction. I think to appease the G.C. I will drop ground rods at the mobile offices and connect them each with a #6 bare copper bonding conductor. Am I right in thinking this. The job was a no bid and price is not that important.

Thanks,
Strugglinsparky
 
You will probably have a couple of issues, since it is coming upon winter, the A/C loads will not be the issue, but the heating load will be. Usually the heat is electric heat strips, because a heat pump would be useless in Colorado, unless they heat with gas in construction trailers in Colorado. The strips draw much more power than the compressors. 50 amps is probably not going to cut it. As far as the ground rods are concerned, you can drive them at the trailers also, because they tie to the EGC, not the neutral, at the trailer.
 
strugglinsparky said:
I have to hook-up two mobile office trailers from one generator. The generator is a 38 KW single phase. The mobile trailers have a exterior panel, and have a 125 amp main breaker. I have been assured by the company that the big trailer draws about 80 amps with the air conditioner running. The mobile offices are expected to be in place for 3 months, but who knows.

My plan is to use 6-4 SJOOW with 4 wire Hubbell 50 amp twist lock to connect to the generator which has a overcurrent of 50 amps, and direct wire to the panels on the side of the mobile offices. It's about 30' from generator to trailer.

I believe this is a solid plan. My question starts when I start thinking about grounding and bonding. I know I should drive a ground rod at the generator, I however do not think I should drive a ground rod at the mobile office. The G.C. is demanding that I do. This is my first job with a this client and do not want to start off with friction. I think to appease the G.C. I will drop ground rods at the mobile offices and connect them each with a #6 bare copper bonding conductor. Am I right in thinking this. The job was a no bid and price is not that important.

Thanks,
Strugglinsparky
Click to expand...

hillbilly1 has a good point on the resistance heating load. Also is it two trailers connected one service panel or two and two?
 
Also is it two trailers connected one service panel or two and two. The two trailers each have their own service panel. I feed each one with a 50a breaker and with both heaters on full today the amperage was about 35 per phase, on the large traler. I told the customer that he would be ok to run small office equipment, but if he were to need to run any power tools, or the microwave to move them to the small trailer with only one heater. Thanks for the response's.
 
Status
Not open for further replies.
Top