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I have a 100-Amp 240-Volt Outdoor Non-Fused Transfer Switch and would like to wire it to the main panel outside. My main panel has 3 breakers (Oven [25 Amp], A/C [50 Amp], & House [100 Amp]) my desire is to tie the Transfer Switch into the service entrance wires that run from the main panel to the sub panel in the garage. (Diagram Below) I already own the hardware so I want to utilize what I have if I can, but don't want to look like a complete idiot when I get someone out there and they go "you can't do that!"

(Note: I plan to hire an electrician to actually wire this up)

I guess my questions are:

  1. Can this be done this way?
  2. Do I need a downline protection device (30-Amp 2-Pole Circuit Breaker) between the Generator and transfer switch?
  3. What are the pitfalls of doing it this way? (aside from the potential for the house to pull more than 30 Amps on that line and pop the breaker.)

Proposed Wiring Diagram

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  • There's a neutral in there somewhere... right???
    – JACK
    Jun 25, 2021 at 17:29
  • @JACK No, not in the diagram. That is why I am hiring an electrician, but I did forget that.
    – Robert S.
    Jun 25, 2021 at 18:27
  • What make and model is your generator? Jun 25, 2021 at 23:02
  • I have a Ridgid RD905712, 5700 Watt Generator
    – Robert S.
    Jun 26, 2021 at 23:04

2 Answers 2

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You'd need to modify the genset to use the transfer switch you're talking about

Your primary problem is that since the transfer switch you're proposing has a solid neutral (i.e. it only switches the two hot legs), and your generator has a bonded neutral (neutral connected to the grounded generator frame), something has to give in order to avoid a case of Two Bonds Bickering at your house whenever you plug the generator in. Such catfights are to be avoided as they result in wayward neutral current going down equipment grounding paths, making exposed metalwork "live" in the process.

The simplest way to do this would be to use a Reliance Controls XRK1003DR instead of your existing transfer switch; this is about twice the price of the GE TC10323R, but lets you consolidate by getting rid of the "spa panel" box outright, as well as moving the inlet into the transfer panel with a Reliance PK30 kit. It also supplies some extra breaker spaces, just in case you're running short on room in your existing panel. You could also keep your transfer switch and modify the genset to break its neutral/ground bond, but that'd require a generator technician since there are no instructions in the manual for that, and also makes the generator unusable for portable power unless the bond is reconnected.

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  • I was unaware of that issue, and I feared something like that... I believe I will sell the current switch I have an purchase one like the one you referenced as this seems to be a better and safer way to get this done... Appreciate the response!
    – Robert S.
    Dec 8, 2021 at 14:59
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I can not see any issues with A transfer switch when in the utility position the inlet will be isolated. With the generator position the utility will be isolated with the exception of the neutral/ground.

The only problem will be the grounding on the generator I can not make out how many conductors you will need both a ground and a neutral and the connection in your gen set may require the bond between the 2 to be removed to prevent a parallel path.

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  • "you will need both a ground and a neutral and the connection in your gen set may require the bond between the 2 to be removed to prevent a parallel path." Ed, I believe you are correct. In the Inlet box there is a neutral and ground but the ground is pre-wired to the box whereas the neutral is meant to be wired into the transfer switch
    – Robert S.
    Jun 25, 2021 at 18:32
  • The neutral can be a direct wire no problem there from the generator to the transfer and to the main (no switch required) but that requires the bond at the generator neutral-ground to be removed as most are not floating ground. I have modified this wiring in quite a few generators for my customers. ( I am an electrician).
    – Ed Beal
    Jun 25, 2021 at 19:48

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