2

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?

8
  • 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, 2015 at 14:34
  • no would be the short answer, they all have to have a common throw,
    – Ed Beal
    Nov 17, 2015 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, 2015 at 15:08
  • @EdBeal Sounds like you know about this. Post as an answer - seems good to me.
    – JPhi1618
    Nov 17, 2015 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, 2015 at 17:15

1 Answer 1

3

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!

1
  • 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. Nov 17, 2015 at 19:22

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.