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I am in the process of attaching a 2-Pole transfer switch to my breaker panel and powering it by a 7500W generator. The generator is neutral-bonded-to-ground. I understand I have to disconnect this in order to power the transfer switch safely. This consists of removing a jumper on the alternator. My question is: Can I install a toggle switch (30A light switch if you will) between jumper on the generator to be able toggle the ground off when connected to the transfer switch and on when using as a stand alone generator?

Tester101
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Barry Campbell
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  • I've never hooked up a generator to a transfer switch, but your suggestion doesn't _sound_ safe just because it seems very easy to forget the toggle switch when using the generator for the two purposes. I'm sure I would forget one day, and I'm not sure how dangerous that is. – JPhi1618 Nov 17 '15 at 14:34
  • no would be the short answer, they all have to have a common throw, – Ed Beal Nov 17 '15 at 14:57
  • took two long to type the explanation so it would not let me edit. If you have a true transfer switch it should have at least 3 poles 2 throws, One goes to the service feed, the center to the load center, the other to the generator, this way you are switching both hotts and your neutral/ground, at no time are your service neutral and generator neutral tied together, If you were to forget to flip the light switch or the contacts welded you would have an very unsafe condition. – Ed Beal Nov 17 '15 at 15:08
  • @EdBeal Sounds like you know about this. Post as an answer - seems good to me. – JPhi1618 Nov 17 '15 at 16:39
  • I was looking up 250.30 to make sure memory served + to ArchonOSX for complete code reff, exibit 250.12 & 250.13 have nice pictures of 3 & 4 pole double throw setups – Ed Beal Nov 17 '15 at 17:15
  • Thank you, everyone. Ed, your information is most informative. I have a Reliance 310A Pro / Tran2 Transfer switch and a Westinghouse 7500W Generator. The generator manual states I must remove the jumper wire if the transfer switch is a 2 pole switch. Reliance confirms what I have is, in fact, a 2 pole transfer switch and the jumper must be removed to operate safely. I just wanted a "work around" to not reinstalling the jumper when I wanted to use it as a stand alone generator. Thanks again. – Barry Campbell Nov 17 '15 at 19:11
  • Is your transfer switch located before your main service panel? Also, where is your existing neutral/ground bond? (It's usually in the main service panel, but a few folks have it in their meter pan instead.) – ThreePhaseEel Nov 17 '15 at 23:14
  • My transfer switch is wired between the generator and the service panel (I think that is the question you are asking), and my neutral / ground is in the main service panel. I didn't stumble across this issue until I had purchased the generator and read about the jumper. I will probably just disconnect the jumper as the manual states and reinstall it if I use it outside of the transfer switch. I was looking for a way to switch it manually to accommodate both scenarios. If this WON'T work, I will have to do it the labor intensive way. Thanks for the responses. – Barry Campbell Nov 18 '15 at 00:23

1 Answers1

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You have two choices.

1) Remove the jumper on the generator, and connect it to the transfer switch as you had planned. But have to put the jumper back on if you ever want to use the generator separately. You also have to hard wire the neutral through the transfer switch.

or

2) You can leave the jumper on the generator, drive a separate ground rod for the generator or connect it to a newarby ground rod with a suitably sized grounding electrode conductor, and change the transfer switch to a 3 pole that switches both phase conductors and the neutral.

Short version is, if you switch the neutral you need a ground rod and a system bonding jumper and if you hard-wire the neutral you need to remove the system jumper on the generator. I agree with Ed Beal putting a switch on the jumper would make it too easy to leave in one position or the other. But then if you leave the jumper on for separate use you may forget to take it off for the transfer switch if you go that way.

Your best course might be to leave it on and use method 2 with a 3 pole transfer switch.

Refer to Article 250.30 for the proper grounding of separately derived systems.

Happy Tuesday!

ArchonOSX
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  • Thanks for that answer. Since I already have the equipment, I will probably go with option 1 as I can't change the transfer switch at this point (and don't know if it's possible to convert it). Thanks again. – Barry Campbell Nov 17 '15 at 19:22