# Portable generator "system ground is not connected to AC neutral"



## Shawn MacAnanny (Oct 27, 2012)

Hey guys, i had a mobile power unit setup that was giving me some problems, so i pulled the lima generator out and im just sticking a cheepo 10kw unit back in its place but i have some concerns about the new generators manual saying that the ground is not attached to the AC neutral. This trailer has a few outlets connected, a couple air compressors and a couple 240v outlets. When i removed the generator it was connect to the power distribution panel with 4 wires, the two hots, going to each ammeter, and the neutral and the ground running together and to a lug on the frame of the trailer/distribution box/chasis ground.

In reading this manual i am concerned that bolting this new dual voltage generator (selectable 240v/120v) may cause issues by not having them connected together at the generator. Am i corrrect in assuming this? I plan on only running the generator in 240v, and connecting it back up just like the larger unit had been that i removed. Should i make a jumper connection at the generator to connect the neutral wire to the frame of the generator? Being this is going to be bolted metal to metal to the chasis what would be the safest way to run this generator? Would this have any effect if i needed to power a house in an emergency? Or am i just reading too much into this excerpt from the owners manual?


----------



## Shawn MacAnanny (Oct 27, 2012)

From what i am reading, i should disconnect the ground wire from the wires coming from the generator to the power distribution box on the trailer. Is this correct? Will it interfere with the function of the air compressor or chasis GFI outlets on the trailer? Or if i were to use it to power a home in an emergency? Maybe the ground should be on a switch to be "ON" when using the trailer and components, and "OFF" when connected to a home?


----------



## aandpdan (Oct 8, 2012)

Hi Shawn,

How do you connect to the trailer? Via a cord and plug? Will you unplug the trailer and plug the house directly into the generator if you need to?

If so, wire the new generator EXACTLY as the old. There should only be one neutral/ground bond. Since you have a panel on the trailer where they tie together you don't have to make any changes. 

For the house, again, you don't have to do anything to the generator. The neutral/ground bond takes place in the panel.

The only likely problem would result when you ARE NOT plugged into the house or trailer. If you plug something, say a saw, into the generator directly there would be no neutral/ground bond. In this case you would need to bond them. 

A little trick, make up a plug with just the neutral/grounds tied together that you can plug into a spare outlet IF you ever run into that situation.


----------



## Shawn MacAnanny (Oct 27, 2012)

Thanks!

The generator will be bolted to the trailer, so the chassis of the trailer will be bolted to the trailer where the junction box for the trailers components are connected, which is in contact with the trailer chassis so the neutral wire and ground feeding into the trailers junction box are making contact with the generators frame this way.

The large generator i removed was wired directly to the sub panel. This new generator i wired in a 6ft 50 amp range cord to plug into the new 50amp outlet on the generator. I have a 50amp outlet coming out of the sub panel on the trailer for a welder to plug into that i was thinking i could power a home from like i could in the past with the larger unit, but now i am thinking i should just unhook the cord i have hooked generator to trailer sub panel, and run a large 50amp cord from the generator to a home if i needed. This would leave the trailer neutral and ground bonded since it has 120v GFI outlets on it, but it would allow the neutral / ground to be broken by directly connecting to the generator to a large 50amp cord to connect to a home right?

So going over this i think i have it. I plug the trailer in, its bonded at the sub panel on trailer, and by the frame being bolted to the trailer chassis. this make the 50amp outlet from the sub panel safe to use with a welder and all outlets on the trailer safe because the neutral and ground are bonded inside of the sub panel.

By unplugging the trailer 50amp plug, i would then plug in a separate 50amp extension cord to power a home. This would then leave the neutral and ground unbonded and safe to use to backfeed an a home panel in an emergency right? I think the old generator was wired wrong in having the neutral and ground connecting if it were to be used to feed a home. Thats what i discovered when removing it.


----------



## aandpdan (Oct 8, 2012)

Shawn MacAnanny said:


> By unplugging the trailer 50amp plug, i would then plug in a separate 50amp extension cord to power a home. This would then leave the neutral and ground unbonded and safe to use to backfeed an a home panel in an emergency right? I think the old generator was wired wrong in having the neutral and ground connecting if it were to be used to feed a home. Thats what i discovered when removing it.


As long as there is only ONE neutral ground bond you are fine. Using a 4 wire cord to plug in the trailer panel OR the house is fine. (The neutral/ground bonds are done at EACH panel.)

I won't go into backfeeding, I'm hoping you're using an approved transfer panel or interlock. But yes, the neutral/ground should not have been tied together. If the house was plugged into the trailer, it would have been bonded by that panel however.


----------



## Shawn MacAnanny (Oct 27, 2012)

Yes while removing the old unit it i found it was bonded to the trailer and it would have been incorrect to run it plugged into the trailer. But plugging directly into the new generator will eliminate this problem so all should be fine now. I havent installed the new generator on the trailer yet, that's tomorrows project but i was going over the manual tonight and saw the neutral being unbonded and led me to start researching what exactly the proper way to ground it was. 

Thanks for all you help!


----------

