Generac Automatic Transfer Switch Install

chriskay301 · Nov 3, 2020

Hello,

I bought a used generator and transfer switch from a Generac installer. He had a customer that was upgrading, so he bought their old one, and then I got his old one. Anyway, it is a 7kW unit with an automatic transfer switch + panel.

The generator is installed, starts up and runs, and I am now working on the wiring. Everything is hooked up on the generator side, but I am having trouble on the transfer switch side.

I understand where to wire the power, grounds and control wires, however, I am unsure where the neutrals go.

The instructions state to move the circuit with the neutral over to the new subpanel. That neutral would go to the neutral bus in the transfer switch/panel and the circuit in the transfer switch panel. The ground for the circuit remains in the main box.

The thing I don't understand is that there is only one lug to hook up a neutral wire. Wouldn't the neutral bus in the transfer switch need to be able to switch between neutrals depending on which source the power is coming from?

jackhammerJIM · Nov 3, 2020

Yes the neutral must be changed over .

pc1966 · Nov 3, 2020

Normally in the UK the neutral is switched over as the source (utility or generator) is often the point of commonality between the neutral (return for current under normal circumstances) and the earth (ground, return for current under fault conditions). The UK regulations do not allow that link N-E to take place inside the installation, or allow there being two links (to avoid spurious circulating currents in the earth structure).

However, the USA and some other places have different rules and so it is possible that the utility neutral is just left connected as all times, even when on generator. Again, in the UK that is a big no-no in case there is a fault and some worker on the utility side is exposed to a "live" neutral due to back-feed from the generator.

Hopefully one of our American members such as @Megawatt can reply as they will knowe far more than I do about this situation.

chriskay301 · Nov 3, 2020

Yes, that was my thought as to why they need to be switched.

So, looking at the pictures, am I missing something as to where the neutrals would hook up to be switched?

I found the picture below on another forum, and it looks like they hooked the generator neutral to the neutral bar main lug, and the one going back to the main panel in a normal spot on the neutral bar.

This would be incorrect, no?