generator transfer switch

[gaston harris]

I'm wiring a manual transfer panel for a generator and have several questions. The panel looks like a main panel (and can actually be used as one) except for the 60A and 30A breakers are arranged so that only one can be on supplying power at a time. http://www.reliancecontrols.com/Prod....aspx?TRC0603C

In the main service panel the neutral and the ground are bonded and I know I must move the breakers from the main panel to the transfer panel. I'm not sure about the wiring for each circuit I move to the transfer panel though. I know I have to extend the hot wire/black to the moved CB in the transfer panel but do I have to extend the neutral and the ground also for each circuit?

I also believe on the transfer switch the neutral and ground should not be bonded just like a subpanel should be wired. Any help is greatly appreciated.
Gaston

[Roger Frazee]

Hi

The transfer panel is wired just like a subpanel with neutral and equipment ground separate.

I am assuming here that you are going to install a double pole breaker in the main panel rated to the same as your transfer panel to get power to it when connected to utility power. You will run 4 wires (H-H-N-Grd) to the transfer panel. If you have metal conduit between panels this can serve as your equipment ground and you will not need to run a ground wire only 2 hots and a neutral.

You do not need to transfer branch circuit neutral and ground wires to the transfer switch panel as your generator will not be a seperately derived system...ie...your transfer switch/panel does not switch the neutral. You remain solidly connected to the utility neutral with your type transfer panel. So moving the neutral and equipment grounds serves no purpose.

So you will connect the neutral of your feeder from the main panel to the neutral bar of the transfer panel and the neutral from the generator to the neutral bar of the transfer panel. Only extend the hot conductor of each branch circuit to the breakers you move to your transfer panel. At the neutral bar in the transfer panel you will have 2 connections. the feeder neutral and the generator neutral. At the ground bar of the transfer panel you will have two connections.... the feeder equipment ground and generator equipment ground. If you ran metal conduit between panels then you will only have the equipment ground of the generator connected to the ground bar.

[gaston harris]

Thanks Roger
It didn't make sense to me to extend the gnd and neutral to the transfer panel either but I've had two people tell me otherwise. I agree with your explanation - if I was switching the neutral in the transfer panel it would be a different story. Thanks again for the help.
Gaston

[Rod Sheridan]

The other issue is that the generator may have to be intended to be used as a standby generator.

The neutral at the generator cannot be bonded to ground at the generator, it must be floating. (At least in Canada).

These generators have a warning sticker indicating that the neutral is floating, in Canada, it is not permissible to field modify the generator, it voids it's approval.

You should check with the local authority having jurisdiction.

regards, Rod.

[gaston harris]

thanks Rod,
As usual I should have asked on the forum before I purchased anything -oh well. I spent hours on an electrical forum reading about exactly what you describe. I wish I had know this before buying the 2 pole transfer switch. Seems the easiest way to use a portable generator with a neutral bonded to the ground with out modifying the generator is to use a three pole transfer to switch the neutral. Thanks again for the heads up.
Gaston

[Roger Frazee]

Portables can either be neutral bonded or floating. Most industrial grade generators are neutral bonded. This is to comply with the grounding requirements of OSHA for a job site generator. The danger in a neutral bonded generator on a two pole transfer switch is the parallel path created between the equipment ground and neutral. Though this is commonly overlooked and generally the danger minimal unless the neutral opens putting all current on the paralleled equipment ground. You should avoid this possibility. Only way to know is to see if your generator is neutral bonded.

This is a long subject. This article does the best at explaining this issue that I have found.......

http://www.schneider-electric.ca/www...pl_Note_EN.pdf

[gaston harris]

Thanks Roger,
I actually found this yesterday in all my searching it was one of the only articles I read that made much sense. It clearly explains this topic. Right now the generator that I'm borrowing from a friend has the neutral bonded to the metal frame of the generator. I was planning on purchasing a Cummins Onan p5450e from Costco and from reading the owners manual it sounds like it has a floating neutral and that you must connect the earth ground once you purchase it. Not completely sure though. I'll call Cummins on Monday to check for sure.
http://www.costco.com/Browse/Product...〈=en-US

Thanks for the article - I've saved it for future reference.
Gaston