Generator Neutral Bonding Issue

Old 12-08-08, 07:33 PM
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Generator Neutral Bonding Issue

Ok I have installed a Briggs & Stratton 7kw (model 040248) stand-by generator and a 16-circuit SIEMENS 2-pole manual transfer switch. I installed everything and once I fired up the generator and plugged into the 240 outlet the 30A GFCI breaker on the generator tripped and subsequently each other time I tried. After playing with it I noticed that if I disconnected the ground from the 4-wire cord going into the disconnect box on the outside, the generator would run and provide power to the house.

I then came in and did some research last night and found that the generator and the transfer switch are by code not compatible as the generator's Neutral is BONDED to the chassis, and technically you would need a transfer switch to "switch the neutrals". Well after a large investment in money and time and no way to take anything back, I am in search of a solution.

One thing I came across was that I can "REMOVE THE BOND" on the generator and everything should work because it would bond to the main panel in the house.

My ultimate question is if this the direction I should take? Are there any other alternatives? If this is the direction I need to go how do I effectively un-bond the neutral on the generator. I have included a link to the "WIRING DIAGRAM" below for assistance. I also have opened up the control panel on the generator and found a screw through the chassis in the back with 4 wires under it (2 white and 2 green), do I remove the whites from the bolt and tie them together and I am done or what are my options.

Also Manual of course says DO NOT REMOVE BOND as GFCI OUTLET WILL NOT WORK AND CAN CAUSE INJURY, but if everything flows down through to the main panel will the GFCI still not work?

I am new to this forum and I thank you in advance for any help.

Old 12-09-08, 08:14 AM
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I should think the solution to this might be a dual use set-up.

A way to use the generator connected to the transfer switch - either a connection before the GFCI on the generator or not bonding of the neutral on the generator.

Then also a way to safely use the generator as a stand alone unit - The neutral bonded and use the GFCI.

This whole thing is complicated and my mind is going in circles!

What I'm thinking of is the power company connection at the power company transformer. How is this wired? Well they ground the neutral at the pole. But there is no GFCI between the electric company transformer and your house!

So I should think a similar setup with the generator would be ok as well, a grounded (bonded) neutral at the power source and no GFCI.

But then looking backwards, you would then have your neutral bonded to ground at your main electric panel which would then sort of be a subpanel, but then this panel would not be supplying power, the transfer switch would!

So with the generator supplying power, would the bonding of ground to neutral at your main panel in any way be a safety issue?

I would say no since the main electric panel would not be carrying any power. However this ground would "translate" to your transfer switch (the neutral bonded to the ground), however the transfer switch would be like a "main panel" as it relates to the generator.

But now we have a different situation from the electric company service and that is instead of 3 wires to the transformer (2 hots and a neutral), you also have a ground wire run to the generator.

So is it necessary to run the ground wire to the generator?

It is not necessary to run a 4th ground wire to the electric company transformer!

(I have no idea what to do in this situation, so don't do anything based on what I have said here. I am just "throwing this out for discussion"!)
Old 12-10-08, 08:02 PM
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I had a little time today and was able to search for and find a transfer switch which is compatible with a generator which has a GFCI.

This transfer switch (B&S) also has a wiring diagram of what it is switching. What it does (as you said above) is to disconnect the neutral from the main power panel and connect the neutral to the generator at the same time. So no GFCI tripping issue.

Thinking about this, I guess this would be the safest solution. Basically all power provided to the house would be GFCI protected. Plus if someone wired something wrong and power was being sent out on to the electric company's lines, these would be GFCI protected as well - or at least up to the power company transformer.

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