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    BigRed1500's Avatar
    BigRed1500 Posts: 70, Reputation: 8
    Junior Member
     
    #1

    Aug 31, 2011, 10:22 AM
    Grounding/Bonding Backup Generator with Transfer Switch
    Grounding question for the electrical pros out there.

    I recently bought and installed a backup generator, and wired it to my main panel via a transfer switch. The system is hardwired with a power inlet box on the outside of my house.

    I have loads balanced between the two phases pretty evenly. It's been tested and is feeding properly whether on utility or generator for lights, fridge, etc. I haven't yet run my furnace on the generator, but I don't see any reason for it to be different.

    I want to make sure that I understand the neutral and grounding requirements for the generator outside so that someone doesn't get hurt standing in snow or wet grass while it's running outside.

    Generator is a Husky 3,750-Watt, Model #30438 (http://www.homedepot.com/buy/electrical/alternative-energy-solutions/husky/generator-3750-watt-77063.html)
    Transfer switch is a Gen-Tran Model #3028 30A, 7500 Watt capacity. (http://www.gen-tran.com/eshop/10Expand.asp?ProductCode=3028)
    Power inlet box installed outside the house is Gen-Tran Model #14302, 30A, 7500 Watt (http://www.gen-tran.com/eshop/10Expand.asp?ProductCode=14302)
    Wire configuration on generator and power inlet box is L14-30, run with 10/4 wire throughout.

    The transfer switch has a separate neutral bar, 1 neutral connected to neutral bar in my main panel, 1 neutral from the generator inlet.
    Transfer switch also has a separate ground lug, same thing - 1 ground going into my ground bar in the main panel, the other coming from the generator wire.

    I have 2 questions, kind of related to eachother:
    1.Neutral - this setup means that the neutral is still connected to the utility even when running on generator. Does this pose a risk of backfeeding any stray voltage and do I need to add a switched neutral kit to it?
    2. Ground - Since the neutrals are connected, do I need to disable the generator frame ground and use a separate grounding rod outside where the generator will be running?

    Thanks for the help.
    Ian
    tkrussell's Avatar
    tkrussell Posts: 9,659, Reputation: 725
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    #2

    Aug 31, 2011, 01:38 PM
    First of all, I really appreciate the detail you provided to explain your question, well done.

    You do not need to change anything, you have connected the neutral and grounding properly.

    You do not need a switching neutral. That is for specific purposes that does not apply to this typical installation.

    Be sure to test your furnace on generator well before you need it.

    Some furnaces use electronic controllers that do not work well with generator power for some reason I am not sure about.
    BigRed1500's Avatar
    BigRed1500 Posts: 70, Reputation: 8
    Junior Member
     
    #3

    Sep 1, 2011, 06:41 AM
    Thanks. So outside, for the generator itself, I do not need to add a separate grounding rod?
    tkrussell's Avatar
    tkrussell Posts: 9,659, Reputation: 725
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    #4

    Sep 1, 2011, 07:06 AM
    Not needed per Code, only if the manufacturer requires a ground rod.
    BigRed1500's Avatar
    BigRed1500 Posts: 70, Reputation: 8
    Junior Member
     
    #5

    Sep 1, 2011, 07:54 AM
    Great, thanks again for the info.

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