Trailer Mounted MEP803a Grounding

[tscott8201]

I'm working on wiring up the house so that I can use my trailer mounted mep-803a as a whole house backup. I'll be using a panel interlock kit so my neutral and ground will not be switched. For this situation, what is the proper grounding arrangement?



Tom

 

[lonesouth]

ground at the panel only. remove neutral ground bar in the generator.

 

[DieselAddict]

ground at the panel only. remove neutral ground bar in the generator.

What he said. Its OK to drive a ground rod at the generator if you like. Removing the bonding jumper at the generator is required to meet code.

 

[tscott8201]

Thanks, That's what I was after.

Tom

 

[Guyfang]

This is something else we should make a sticky. This question gets asked 5 times a week.

 

[Dwnorton1]

I would also bond the trailer and the generator ground together as well to be on safe side and inspectors like the ground that they can see. The reason it is so important to ground your gen set before running is as follows:
Lets say L2 shorts out to frame of generator, what would happen? Nothing. How can they be you say? The 120vac has no reference to know it is shorted so gen will merrily run until you come up and touch it to turn it off, then you gave it a ground reference, you. I for one don't care much for being an electrical conductor. Been there done that can still taste the fillings in my teeth.

Any electrical device used on a house wiring circuit can, under certain conditions, transmit a fatal current. While any amount of current over 10 milliamps (0.01 amp) is capable of producing painful to severe shock, currents between 100 and 200 mA (0.1 to 0.2 amp) are lethal.

OSU

There is safety presentation for today. Be safe out there.

 

[Ken_86gt]

I would also bond the trailer and the generator ground together as well to be on safe side and inspectors like the ground that they can see. The reason it is so important to ground your gen set before running is as follows:
Lets say L2 shorts out to frame of generator, what would happen? Nothing. How can they be you say? The 120vac has no reference to know it is shorted so gen will merrily run until you come up and touch it to turn it off, then you gave it a ground reference, you. I for one don't care much for being an electrical conductor. Been there done that can still taste the fillings in my teeth.

Careful with your words as this might be misconstrued! Only one neutral ground bond in the system is allowed by code. Only One. If you have a bond in the panel that the generator is connected to then there should not be one at the generator, instead just ground the generator frame with a ground rod. More than one bond in a system creates circulating currents on the grounding conductors and this poses a safety risk of shock. To keep it simple lets not get into low impedance grounding circuits and all of the other scenarios - grounding can get complicated so my philosophy is to keep it simple.

If your generator is the only source of power in the middle of a field and not connected to any other service- then yes, bond the neutral and ground - and then drive a ground rod for the generator.

 

[DieselAddict]

Careful with your words as this might be misconstrued! Only one neutral ground bond in the system is allowed by code. Only One. If you have a bond in the panel that the generator is connected to then there should not be one at the generator, instead just ground the generator frame with a ground rod. More than one bond in a system creates circulating currents on the grounding conductors and this poses a safety risk of shock. To keep it simple lets not get into low impedance grounding circuits and all of the other scenarios - grounding can get complicated so my philosophy is to keep it simple.

If your generator is the only source of power in the middle of a field and not connected to any other service- then yes, bond the neutral and ground - and then drive a ground rod for the generator.

I think he didn't meant bonded as it is used in the NEC. I read it as connecting the ground to the trailer. I certainly agree with that.

As as a general FYI the term "bonding" as it is used in the NEC describes connecting the ground and neutral together. It doesn't describe connections in general. In the code it has a specific meaning. It is very common to confuse it as describing general connections.

The section of of the code is titled "Grounding and Bonding".

 

[Dwnorton1]

That's why I'm always hesitant to try explain. I work in offshore oil industry. We bond all equipment to deck. The structure is the ground. When I said bond I mean ground lug to ground rod as well as "visible ground tapped to structure. No bolt thru's." Neutral is only bonded to ground at one point. Distribution panel.

In my generator hook up,1ph 240vac, I use a 4 wire (conductor decided by unit) H H N G. So in effect I gave a huge ground system considering I have 6 separate ground rods in my grid of panels and sub panels. I carry neutral throughout complete system as well.

More eloquently put by gentlemen above.

 

[DieselAddict]

That's why I'm always hesitant to try explain. I work in offshore oil industry. We bond all equipment to deck.

Technically you grounded it. Bonding is something else.

 

[Dwnorton1]

Technically you grounded it. Bonding is something else.

True by NEC. Terminology 101 Lol. All of our skids are "grounded" with external wire, even if welded to deck. Little known fact that loose electrons are attracted to the green of the wiring insulation and will orderly march way over to ground wire during fault. Hence need for ground.