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Electrical Wiring for Generator Connections

Why you should never connect a generator in such a way as to back-feed your electrical system. This is extremely dangerous not only to your home but also the electrical utility crews who may be working on downed electrical wires.

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Wiring Connection for a Generator

Question: I have a Generac 8550/5550 heavy duty generator with 120/240 30amp AC. I ran a Type NM-B 10/3 600v wire into the garage to plug into the dryer, but after reading up on this bad idea. I was wondering if I could take the wire into a stand alone panel box and run smaller circuits into the house to plug in refrigerator, window ac, lamp and maybe a TV on different outlets.

This question is from Guy a Handyman in Jacksonville, Florida.

Additional Comments: This is a great website. Really nice for someone to share their wisdom with others. Thanks

Electrical Connections for a Home Generator

Skill Level: Advanced. This electrical wiring project is best performed by a Licensed Electrical Contractor or Certified Electrician. Not Recommended for Homeowners.
Tools Required: Electricians pouch of hand tools and the various power tools necessary for installing the generator and transfer switch.
Estimated Time: Depends on the type and size of the generator and transfer switch and the available access to the project area.
Precaution: Any existing electrical wiring within the immediate area that may interfere with the installation of the transfer switch may need to be relocated if necessary.
Important: Installing a generator and transfer switch must be well thought out and performed with a permit with all work being inspected.

Wiring Circuits for a Home Generator

Dave’s Reply:
Thanks for your electrical question.
Hello Guy – You are absolutely correct.
IMPORTANT: Never connect a generator in such a way as to back-feed your electrical system! This is extremely dangerous not only to your home but also the electrical utility crews who may be working on downed electrical wires.
The Solution is to install a Transfer Switch and Sub-Panel specifically for essential circuits that you need to have on generator power. This is not advisable for a novice and it is best to have a licensed electrical contractor install this setup for you. This project should be done with an building permit and inspection.

More about Installing a Generator and Transfer Switch

Home Electric Generators

Residential Electric Generators

This series covers a wide variety of topics all about home generators including sizing, selecting, connecting and safely operating this all important addition to your home.
Generator Section
The Importance of a Generator Transfer Switch

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Be Careful and Be Safe - Never Work on Energized Circuits!
Consult your Local Building Department about Permits and Inspections for all Electric Wiring Projects.

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2 Responses to “Electrical Wiring for Generator Connections”
  1. Matt says:

    I recently purchased a Honda EM6500 portable generator and had a electrician install a sub panel and transfer switch. Before energizing it, he tested the generator and found that it was getting 8V through the ground. He indicated that this is too high of a voltage running through the ground and this could damage our TVs, computers and refrigerators.

    I have had numerous conversations with the dealer for this generator who has contacted Honda. They claim that this is a tolerable amount of voltage, of course I have no proof of this conversation other than my dealer’s word.

    I have two questions:

    1) Do you think that this level of voltage through the ground is considered normal operation for a unit like this (my understanding a top of the line generator)

    2) Do you agree or disagree that this level of voltage through the ground presents a real risk of damaging sensitive equipment in my house?


  2. Dave Rongey says:

    Hi Matt,
    I do not like the idea of any voltage on a ground system except when a fault occurs, and that would be for a very short period of time until ground fault protection reacts and opens the circuit. For some power supplies and such equipment the ground is used as a reference, however that should not appear as a static reading of voltage on the circuit ground at all times.
    I would think that if the ground of the generator were bonded to an earth ground that the reading would disappear, and if that proved to be the case then the problem of voltage on the ground would be solved, however that still does not explain what is causing the voltage to be there on the generator side.
    It would be good to take a series of readings, especially when a load is added to the generator.
    I will do further research and add any significant discoveries.

    This is an open comment, and other views are encouraged.