Grounding/Bonding a Portable Generator

[mystereons41]

I am using a portable generator that I will only be using with cord and plug connected equipment. I have checked with the meter and the neutral and ground are not bonded. The manual states that the frame needs to be earth grounded.

My questions are:

1. Should the neutral and ground be bonded? From what I understand, since the system is not connected to the house service panel, the neutral and ground should be bonded on the generator. This is to prevent electric shock/fire by providing a low resistance path for current and thus allowing the GFCI to trip in an emergency. Is this correct?

2. Does the frame need to be grounded? According to NEC:

250.34 Portable and Vehicle Mounted Generators

(A) Portable Generators. The frame of a portable generator shall not be required to be connected to a grounding electrode as defined in 250.52 for a system supplied by the generator under the following conditions:

1) The generator supplies only equipment mounted on the generator, cord and plug connected equipment through receptacles mounted on the generator, or both and

2) The normally non current carrying metal parts of the equipment and the equipment grounding conductor terminals of the receptacles are connected to the generator frame.

The first condition is satisfied because I am using only cord and plug connected equipment through receptacles mounted on the generator.

The second condition I think is requiring the neutral and ground to be bonded. Is this correct?

I think what I have determined so far is that for my use, the neutral and grounded should be bonded and that I am not required to earth ground the frame.

But I wanted to double check.

Any thoughts would be appreciated!

 

[Little Bill]

I am using a portable generator that I will only be using with cord and plug connected equipment. I have checked with the meter and the neutral and ground are not bonded. The manual states that the frame needs to be earth grounded.

My questions are:

1. Should the neutral and ground be bonded? From what I understand, since the system is not connected to the house service panel, the neutral and ground should be bonded on the generator. This is to prevent electric shock/fire by providing a low resistance path for current and thus allowing the GFCI to trip in an emergency. Is this correct?

2. Does the frame need to be grounded? According to NEC:

250.34 Portable and Vehicle Mounted Generators

(A) Portable Generators. The frame of a portable generator shall not be required to be connected to a grounding electrode as defined in 250.52 for a system supplied by the generator under the following conditions:

1) The generator supplies only equipment mounted on the generator, cord and plug connected equipment through receptacles mounted on the generator, or both and

2) The normally non current carrying metal parts of the equipment and the equipment grounding conductor terminals of the receptacles are connected to the generator frame.

The first condition is satisfied because I am using only cord and plug connected equipment through receptacles mounted on the generator.

The second condition I think is requiring the neutral and ground to be bonded. Is this correct?

I think what I have determined so far is that for my use, the neutral and grounded should be bonded and that I am not required to earth ground the frame.

But I wanted to double check.

Any thoughts would be appreciated!

I think you have mostly answered your own questions with the exception of what you stated in red above. That (2) is not saying to bond the neutral and EGC, it is saying that anything metal not normally carrying current and the EGC terminals should be connected to the generator frame.
Welcome to the Forum.

 

[suemarkp]

I don't see a requirement to bond neutral and ground. Normal thought goes out the window with an unbonded system. A fault isn't a hazard if the generator is not bonded because there is no reference to earth. You can bond neutral and ground if you want to, but I don't think it helps much.

One thing about grounding the frame is for dissipating static electricity build up. This seems to be covered in more recent rules indicating generators over 15KW must be grounded (not sure if that is just an OSHA or UL thing, or NEC too). But a metal framed generator sitting on the earth should bleed out any static build up. If it is on rubber tires, you may want to give the frame some better path to earth (paths for static electricity can be in the K ohm range). They make static dissipators for cars. You can frequently seem them under police cars -- looks like a little flex strip about 1" wide and a half inch thick dangling down onto the pavement.

 

[mystereons41]

Thanks both for the input! I will keep your suggestions in mind

 

[jwelectric]

I don't see a requirement to bond neutral and ground. Normal thought goes out the window with an unbonded system. A fault isn't a hazard if the generator is not bonded because there is no reference to earth. You can bond neutral and ground if you want to, but I don't think it helps much.

If the ground fault path is not bonded to the neutral how do you suppose it is to clear the fault?
Just what part does earth play in clearing a fault?

 

[M4gery]

If the ground fault path is not bonded to the neutral how do you suppose it is to clear the fault?

It won't clear a fault. But on the flip side, a fault is not dangerous to you.

A fault is only dangerous in a conventional system because we purposely bond neutral to ground/Earth. If we didn't do that, you could dance around in puddles holding a hot wire and not get shocked.

Just what part does earth play in clearing a fault?

Nothing anymore.

 

[jwelectric]

It won't clear a fault. But on the flip side, a fault is not dangerous to you.

A fault is only dangerous in a conventional system because we purposely bond neutral to ground/Earth. If we didn't do that, you could dance around in puddles holding a hot wire and not get shocked.

Well what about one winding of the generator fault to ground but the appliance is plugged into a device that is supplied by the other winding? What is the potential at the appliance?

Remember that the equipment grounding is bonded to the frame but the neutral point is not.

Don?t think it would much matter if you were standing on 10 inches of rubber matting or water puddle or whatever as all the potential is in one?s hand should it be something like a drill that is plugged in.