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Powering Detached Garage from Generator

gump1376

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Jan 6, 2021
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NM
Good Day! Long time lurker, but first post. I didn't see anything similar, but my question is,

Has anyone powered a detached garage/shop from a large generator?

Reason I ask is our house has a 200amp service which goes to our 200amp panel in our house. Which then goes and powers the main detached garage (120V only) and our guest house (100amp service panel). We don't have any further room for another set of breakers in our panel and the run to what we call the RV garage (what I want to power) would be well over 250 feet. So burried line would be 00 or larger wire but wouldn't really have that many amps for using a welder or plasma cutter. I also asked the County if we could get another transformer/meter and we need another 1/2 acre in order to do that, unfortunately. So my thought was to use a generator and build out the RV garage as a small shop that I could work in and have our main detatched garage for actually housing our daily drivers instead of my wifes car and my project(s).

I was thinking of something similar to the Duromax 15,000 watt dual fuel portable generator. (https://www.duromaxpower.com/produc...ric-start-dual-fuel-hybrid-portable-generator). The RV garage is a single bay metal building of ~20' wide by ~40' long and 16' tall. Anytime I wanted to work in the shop, I'd roll the generator outside and plug it in and then I could have power for the following: LED lights, exhaust/intake fans for when it's hot out, 60-80 gal air compressor, 9000 lb 4-post lift, and enough juice to power either a welder or plasma cutter and other metal fabrication tools.

If this is something that's workable, then I'd probably add a second story to the back portion for storage of parts so I can get them up and out of the way. I'd also put in some walls with quite a bit of insulation for better control of heat and cold for working in the summer and winter.
 
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mm08822

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Jan 13, 2012
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NJ
You can make it safe and be ready to one day connect a permanent supply to the shop.

Install a "sub-panel" with a main disconnect and isolated neutral block in the shop.
Drive 2 grd rods and connect to ground block.
Wire all of the needed circuits directly back to the panel.
Install a Power Inlet Box (PIB) in the intended generator location.
install a 50A 2 Pole CB with interlock to the main cb (there is no feed to the main cb, but ready to accept one).

This makes all of your wiring permanent, safe and can locate anything where it is needed, instead of an extension cord jungle.
You probably can't get this inspected as I don't think it would pass w/o a permanent source of power provided. At least it would be safe.

If one day, you need more power, then consider the permanent feed. All wiring within the shop would be ready w/o modifications needed.

Generator would need to be bonded for this use. I would install a toggle switch on gen to change between bonded/unbonded.
 
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nadogail

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Jan 23, 2009
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Location
Coronado, CA
I have a generator that I use to power my welder and air compressor on remote jobs.

It’s a “Home Brew” with a 13 Horse Engine and a 10 KW Peak alternator. I welded together a cart from scrap steel pulled from a Dumpster and casters from a old shopping cart.
 

dcg9381

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Jun 20, 2018
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11,968
Location
Austin, TX
We can power the shop with a 10kw generator. Shop has a generator inlet (50A) and main panel has an interlock.
A 10kw generator is loud... With a 15KW generator, you're going to need to investigate what the next step up is from standard 240V @50A 14-50R to be able to use that power. Most generators of that size are hard wired.
 

mm08822

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Jan 13, 2012
Messages
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Location
NJ
We can power the shop with a 10kw generator. Shop has a generator inlet (50A) and main panel has an interlock.
A 10kw generator is loud... With a 15KW generator, you're going to need to investigate what the next step up is from standard 240V @50A 14-50R to be able to use that power. Most generators of that size are hard wired.
Yeah, he could also consider 60A PIB also. L14-60/14-60. Might have to make that. I've only seen up to 50's. I doubt OP needs the full 15KW anyway.
 
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exranger06

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CT
You can make it safe and be ready to one day connect a permanent supply to the shop.

Install a "sub-panel" with a main disconnect and isolated neutral block in the shop.
Drive 2 grd rods and connect to ground block.
Wire all of the needed circuits directly back to the panel.
Install a Power Inlet Box (PIB) in the intended generator location.
install a 50A 2 Pole CB with interlock to the main cb (there is no feed to the main cb, but ready to accept one).

This makes all of your wiring permanent, safe and can locate anything where it is needed, instead of an extension cord jungle.
You probably can't get this inspected as I don't think it would pass w/o a permanent source of power provided. At least it would be safe.

If one day, you need more power, then consider the permanent feed. All wiring within the shop would be ready w/o modifications needed.

Generator would need to be unbonded for this use. I would install a toggle switch on gen to change between bonded/unbonded.
You can't have the neutrals unbonded in the panel AND have the generator's neutral unbonded. Neutral has to be bonded to ground at some point, or the EGCs won't work at all. I would keep the generator bonded and keep the neutrals in the panel isolated.
 

mm08822

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You can't have the neutrals unbonded in the panel AND have the generator's neutral unbonded. Neutral has to be bonded to ground at some point, or the EGCs won't work at all. I would keep the generator bonded and keep the neutrals in the panel isolated.
You are correct. 👍 I was flipping back and forth between sub-panel use and main panel use (with/ without feeder) and inverted this detail.

Corrected now.
 

TractorJeff

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Dec 8, 2013
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Elkhorn, WI
I tried the generator route while finishing the Shop. It was OK (sort of), till Wintertime when you had to drag it outside in the dark(6pm) to start it. Then I sort of felt bad for the neighbors that could probably here it running?
 

RPH

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Dec 17, 2006
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4,190
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Michigan Thumb
The noise, the noise. I go to the shop for peace and quiet. If I make noise that’s one thing but the generator running kills that peace and quiet. I have had to do it here for quite awhile. Now I avoid it if possible. Plus it’s the most expensive electricity money can buy!
 
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