Transfer switch- only connect hot lines for circuit

Question

I have a Generac automatic standby generator with a 8 circuit transfer switch.

I was wondering if because the neutral bars in the main breaker panel are directly connected to the neutral bar in the transfer switch subpanel, could I simply only connect the hot wire of the circuit to the transfer switch breaker, and leave the neutral in the main panel.

Only the hot lines are switched. The neutral lines are not switched. The main panel is hooked to the ground spike and all the grounds run through the main panel ground, and the neutral/ground bonding only happens in the main panel.

I was looking at connecting the circuits from the main breaker panel to the transfer switch sub panel. I was going to connect them by running the hot AND neutral wires for each circuit from the transfer switch to the main panel. Disconnecting the hot AND neutral lines from the breaker and neutral bar in the main panel, and using wire nuts to connect them to the wires to the transfer switch. Inside the transfer switch sub panel, the hot wires would be connected to the circuit breaker, and the neutral to the neutral bar. I would leave the ground wires connected to the ground bar in the main panel.

The neutral bar in the transfer switch sub panel, is connected to the generator neutral and to the neutral bar in the main panel. The ground/neutral bonding happens only in the main panel.

Or, do I have to move the neutral as well, even though the neutrals are all always connected to each other.

I couldn't find any answers that directly matched my question

It is a 8 circuit Generac transfer switch. Essentially, it is a normal 8 circuit breaker panel, but with an automatic transfer switch at the top. The 8 circuits that need to be backed up are all currently in the main panel. The directions have the neutral from the main panel hooked AND the neutral from the generator panel, hooked up to the neutral bar in the transfer switch panel. The neutrals from the main panel, sub panel, and generator, are always connected to each other.

So, I was wondering if I still needed to move the neutral wires from the bar in the main panel, to the one in the transfer switch panel. If the neutral bars are permanently connected, does it matter which bar their on

This page has all the stuff on the generator and the transfer switch https://www.generac.com/service-support/product-support-lookup/product-support-details?productid=024662fe-9257-449e-9290-86a521bf142d

EDIT

There was a large storm recently and power was out for about 4 days, so I got it hooked up and running and an electrician checked it yesterday and said it was good.

Ok, so the generator cable is a 8/3 + 10/1 + 18/6 TC-ER-JP 600 Volt Direct Burial Power and Data Tray cable.

The circuit breaker was drywalled into the wall between studs, and at some point in the past some circuits were added that went through a couple bottom knockouts, and they sprayed foam insulation in the drywall hole. After ripping apart the drywall above it, I could access two of the top knockouts, fortunately, the main power cable comes in from the bottom knockout, so I still had access to the top knockout that can has rings so can do 1.0, 1.25,.1.5, or 2.0 inch depending on how many rings you remove after the center 1.0 inch circle is removed. I also had access to a 3/4 inch knockout on the top. I had no access to anything else.

That comes through the wall into a junction box because the cable he bought was about 5 feet too short. Inside the junction box the 8/3 is connected to three 8 gauge THHN wire, they were out of some gauges because of the storm and supply chain issues from covid, so I connected the 10/1 ground wire to 8 gauge THHN wire, and I connected the 16/6 wires to 14 gauge THHN wire. I also used 10 gauge THHN for connecting all the circuits. In the junction box I also connected a short 8 gauge wire to the nut connecting the grounding wires between the generator and the transfer switch, wrapped the copper end of the stub wire around the junction box grounding screw and screwed it in.

My understanding is that it is ok to use a thicker wire than the other wire in the run as long as the thinnest wire is rated for the maximum current going through the circuit and the breaker/fuse is sized for the weakest wire.

There was not enough room to maneuver solid conduit, and keep it within 24 inches for the 16 10 gauge THHN wires for the 8 backed up circuits.

1. I used 1 inch LFNC-B to connect the generator tray cable from the junction box to the transfer switch.

2. I used 1 inch LFNC-B just under 24 inches, to connect all 16 of the 10 gauge THHN wires for the 8 circuits

3. I used 3/4 inch LFNC-B to connect four 8 gauge THHN wires from the 50 amp double pole breaker in the main panel, to the transfer switch. The 2 hot wires, a neutral, and a ground.

On the individual THHN cables. To identity wires better.

I used black, red, white, and green colored wires for the 8 gauge wires used for the power and ground wires connecting both the generator tray cable on the junction box to the transfer switch, and the wires connecting the 50 amp double pole breaker in the main panel to the transfer switch.

For the 8 circuits moved to the transfer switch, I used black and white 10 gauge THHN wires. Black for live and white for neutral.

I put a label sticker from a label maker on each end of each individual THHN wire. The label on the wires for each of the 8 circuits, was just several rows of 11111111 to 88888888 on the blacks and the same on the whites. The 8 gauge colored wires for power, just are labeled Generator or Main Panel.

When moving a circuit, i used the same numbered black and white 10 gauge THHN wires. For example, for the 5th circuit I moved, I used the black wire with the label that had rows of 5s on it and the white wire with the 5s on it. To make it even easier on the future, I also wired each numbered black wire to that number circuit breaker in the transfer switch.

Answer 1

Neutrals need to come over with the hot(s). Always.

Anytime you bring a circuit over from one panel to another, you must bring all conductors. That means all hot(s) and neutral.

You do not need to bring over safety ground. That is not a normally active conductor, and does not flow current except during fault conditions (which should last milliseconds, not long enough for heating and metal fatigue effects of imbalance current to develop).

Connect the panels with metal conduits

Your best bet operationally is to connect the panels in question with one or more metal conduit passages.

I very strongly recommend EMT non-flexible metal, because EMT takes care of ground for you.

If the conduit will be less than 2 feet long, one large one will suffice, but I'm a fan of multiple. If the conduits will be more than 2 feet, then you need to have multiples, because you can only have 1 large feeder per conduit and 4 small branch circuits per conduit (for thermal derate reasons - you can have more, but you must upsize wires if you do, and that upsizing requires larger conduit).

4 circuits per 1/2" conduit is a happy number for circuits of 15-20A (#14-#12) size. For instance, 1/2" conduit will just fit 5 circuits if some are #14, but "5 circuits" requires going up a wire size and now it won't fit!

Keep them together

All wires of a circuit must be in the same conduit and must be marked to indicate they are together. For instance I use colored tape (tape markings on THHN individual wires do not change neutrals into hots)... so you'll have blue circuit, red circuit, etc. But you can also simply bundle the hots and neutral with black tape or shrink tube.

All hots + neutral of a circuit must go through the same conduit pipe or cable.

Multi-wire branch circuits

Sometimes you see a circuit, properly called a Multi-Wire Branch Circuit or MWBC, where 2 hots in a cable share 1 neutral. Both hots must be kept with the neutral. Further, they must attach to a 240V breaker, or 2 individual breakers with an approved handle tie. Manually shutting one off must shut the other off. Obviously, they can't be in different service panels.

So if you want to put half of a MWBC on a generator panel (which would raise interesting questions about what to do about neutral), you must put all of the MWBC on the generator panel. (which moots those questions).