Building a J-box for your genny.

[lonegunman]

I was wondering what you guys use to power equipment off your gensets?

I won a MEP-002 a couple of months ago and built a junction box of sorts, we used to do this in the military and I like the idea.

Basically I bought a waterproof flexible power cable for an a/c or spa, 6 feet long with three 8 guage wires and added a bare copper ground to the conduit. I attached it to an 8"x8"x4" all weather plastic box that I attached two 15/20a 110 outlets to the outside and a 3wire 250V generator plug to the top of the box.

I used a 4"x4" outlet box that I cut down as a base for three strips and attached all the wires to that on the inside.

The whole thing costs under a hundred bucks and witht he MEP002 set for single phase 120/240 you get 30amps of 240 and four 120 outlets or all of the amps in 120.

My plan is to attach a 30amp gen plug to the shop and use the unit for power after opening a manual switch to kill commerical power. I mostly want to have some lights, the fridge and well pump available and do not need massive power for the house or shop. We have wood heat.

 

[SCSG-G4]

I got a surplus Power Distribution Panel. As originally built, it had an input and output for three phase at 60 amps per phase. I've changed that to allow for 50 amp 208 input driving only phase A and phase B (50 amp RV plug) on the old output side. The output plugs are locking connectors (NEMA L5-20 and L5-30) two of each (one of each per leg) and a straight plug for phase C. I've got a bit more to do to finish up the unit, but it should be good to hook up to a single phase 110/208 generator, or to a GI 3 phase and use all five outlets.

 

[glcaines]

I would highly recommend using a manual transfer switch to switch from commercial power to the generator. That way it is impossible to have a problem with feeding back up the line. Also, if you are not using the ground for your house back to the generator, you will need to ground the generator. However, if you are using the ground for the house, do not separately ground the generator.

 

[SCSG-G4]

If I was to use my setup at the house, what I wanted to run would be disconnected from the wall sockets and plugged in to the PDP, which would be plugged into the generator. The PDP has its own ground connector on the end of the box.

Gary is right - never mix generator and commercial power, even on the neutral/ground side!

 

[cranetruck]

I'm working on a box like lonegunman's and will post images when done. It will include a 3-wire 50A/220 volt socket for a stick welder...

 

[cranetruck]

Here is the junction box. Still needs a strain relief for the cable and a crab handle of sorts.

 

[Coldfusion21]

Nice! I like this idea, Great for field work/repair.

 

[lonegunman]

That actually looks pretty close to mine. I added four 115V outlets to the sides of the box as well. Running the 5KW with a two 1500W heaters in the outlets and running the basic house stuff did not seem to bog it down. I do have an electric shop heater that killed it hard, it is a max amp draw for a bit to long to get it going.

I did put rain resistant covers on everything for outrdoor use.