What do I do with the neutral and ground when wiring a transfer switch?

Question

I know there are a lot of questions about wiring a generator to a home electrical panel, but I can't find the answer to the questions that I have.

I would like to wire a generator that has the neutral bonded to the frame, to my main panel. The GE panel that I have has no "MAIN", It has four 240 volt breakers that are labeled "MAIN SECTION", and eight 120 volt breakers labeled "LIGHTING SECTION". One 60 amp breaker from the MAIN SECTION feeds the LIGHTING SECTION.

I have a manual two pole 60 amp transfer switch that I would like to use and wire the 60 amp MAIN SECTION breaker to the switch, then back to the LIGHTING SECTION buss. What's confusing me is how to run the ground and neutral wires. I wanted to included a wiring diagram with this, but I can't figure out how.

1. Do I bond the neutral to the transfer switch with the bonding screw?
2. How do I run the neutral and ground from the generator to the main panel with a bonded generator?
3. Do I wire the generator frame to a ground bar?

Answer 1

There can only be one point in the system where neutral and ground wires are joined, and this is usually in the main panel. Therefore, you must lift the bond from the generator, or disconnect the ground wire from the generator to the transfer switch.

If you lift the bond on the generator, you can run both ground and an insulated neutral back to the transfer switch. You will also run ground and insulated neutral from the main panel to the transfer switch, and ground and insulated neutral to the subpanel from the transfer switch. Note that neither neutral nor ground are switched in the transfer switch. The generator can optionally be grounded to a rod.

If you cannot lift the bond, disconnect the ground wire to the transfer switch at the generator (or don't run a ground wire at all). The subpanel will still be grounded from the unswitched ground wire from the main panel. The generator cannot be grounded to a rod because this would tie the neutral to ground in a second location through the bond.

Answer 2

This all depends on whether the generator is designed as a separately derived system, or a non-separately derived system.

Most residential generators work just fine as a non-separately derived system. Essentially meaning the neutrals and grounds are separated just like a sub-panel would be, both at the transfer switch and generator.

Also, by NEC Code, a supplemental grounding electrode "Ground rod" could be installed at the generator to help facilitate ground fault detection, but isn't required if over current protection is integral at the generator.

So, you may be wondering why there exist separately derived systems? This is because in commercial and industrial establishments, especially in hospitals, there may contain multiple generators and doing so makes the electrical protection more sensitive to current divsion on the neutral.

Answer 3

User315 is completely correct from a technical viewpoint.

I will add, touching the generator, while standing on the ground, are a generator ground rod, no option.

Being the path of least resistance, sucks.

Answer 4

The transfer switch is service equipment. It disconnects and reconnects service from two sources. As service equipment, the neutrals (grounded conductor) must be bonded to ground ( grounding conductor). This serves the following purposes 1). It provides the utility company with a better neutral. 2). It provides a ground fault path. Providing for safety. 3). It makes the entire system more energy efficient.