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There is tons of information on "bonded neutral" and "floating neutral" generator wiring to transfer switch. However, I have one question I cannot find the answer.

I recently bought a Reliance Control Transfer Switch TF151W (2-pole transfer switch) for the furnace, because I cannot use an extension cord for furnace. In North American, all service panel in our houses have Neutral (white) and Ground (Green/bare copper) connected/bonded by code. In this case, the ONLY option for me is to buy a "floating neutral" generator in order to avoid the dangerous "double bonded" scenario.

Say I want the generator to power my (1) furnace via transfer switch and I want to power my (2) gas water heater using extension cord plugging it into the outlet of the generator. Will there be a problem?

Say, the Generator is "Floating Neutral", I have:

Generator Outlet #1 -> Transfer Switch AC Panel (bonded) -> Furnace

Generator Outlet #2 -> Extension cord -> Gas water heater (not bonded)

My question is: If I unplugged #1 and only run #2, the gas water heater is running on floating neutral. But what if I run #1 and #2 at the same time, will all the outlets on the generator automatically turn into bonded neutral?

Reason I ask is that some gas water heater is very sensitive, they won't start if they detect it is not grounded.

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  • Why are you needing to run an extension cord to a gas water heater?
    – mmathis
    Apr 26, 2018 at 21:10
  • @mmathis Maybe a tankless gas heater that needs it for ignition. A regular gas heater would have a pilot light. Actually, I just some water heaters at Home Depot that have all kinds of connectivity, remote temperature setting, etc. - but the question is whether such a heater could run in a "just heat the water" mode if it has no electricity.
    – manassehkatz-Moving 2 Codidact
    Apr 26, 2018 at 21:35
  • @manassehkatz it needs mains electricity just for SCADA? You'd think they could power a PLC and wifi off a thermopile... Or some well placed Peltier devices...
    – Harper - Reinstate Monica
    Apr 26, 2018 at 21:53
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    @manassehkatz many newer gas water heaters use induced draft and need it for that + use it for ignition as well
    – ThreePhaseEel
    Apr 26, 2018 at 22:24
  • Can you return the transfer switch you have and get a different one? You're better off trying to make this as properly wired as you can...(i.e. making it so you just plug the generator in in one place, flip a switch, and have things go). Also, how much current do the furnace and gas water heater each draw?
    – ThreePhaseEel
    Apr 26, 2018 at 22:25

1 Answer 1

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Lets start with your premise that you must buy a 'floating neutral generator'. That is simply not true, you can buy code compliant transfer switches with neutral-grounding disconnects built in as described in this video.

Next, you seem to be worried about a possible 'transient voltage;' created by double bonding your generator. This will only occur if the generator is already self-bonded (bonded-neutral), and wouldn't be a concern in the scenario you described.

However, your concern about trying to power a water heater with a floating generator via extension cord isn't misplaced as water heaters often will not run if they detect a lack and unbounded neutral. Thus if you were to ever try to run the generator to power your water heater without it also being connected to the electrical panel for your furnace (such as having having your your transfer switch turned off), you may experience an error.

To fully wrap you head around this, I found this video explained exactly what bonded-nutural is and the type of power a floating-neutral generator produces

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  • Thanks a lot for your reply. I actually saw both videos before :) I realized that there is 3-pole transfer switch (EZ Generator Switch) on the market. But I was thinking if I can keep my 2-pole Reliance transfer switch and if i am able to make it work, then life is much more simpler. I understand the 2nd video what he is doing, and that's exactly I want to confirm my original question. In order words, you agree that if I run switch my transfer switch to "generator mode", my sensitive gas water heater should run, right? Base on 2nd video, all outlets will turn into bonded neutral.
    – userb00
    Apr 27, 2018 at 3:17
  • Sorry, about not being more clear. Hopefully my edit to the answer make it more clear that you must also have your furnace active (or be tied into the and actively interacting with the panel in some other manner) to be confident your water heater won't throw an error.
    – virtualxtc
    Apr 27, 2018 at 18:09

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