How to Ground a Portable Generator and Make a Power Box

By Dave Rongey - Summary:

How do I make an extension cord to extend the power from my generator out to a work area? How to Extend the Power of a Portable Generator.

Making a Receptacle Power Source from a Portable Generator

Electrical Question: How do I make an extension cord to extend the power from my generator out to a work area?

  • I have a 3 wire 240Volt outlet from a portable generator.
  • I am making and extension cord to extend the 240Volt out to the work area.
  • Can I also make a 120Volt outlet from this wiring configuration?
  • Grounding the Portable Generator
    Note that the generator is on a truck and ground strapped to the frame of the truck.

This electrical wiring question came from Chuck, in Phoenix, Arizona.

Dave’s Reply:
Thanks for your electrical wiring question Chuck.

How to Extend the Power of a Portable Generator


Wiring Configurations for Portable Generators

  • 3Wire Generator Plug
    The generator that has been described has a 3-wire outlet, which does not have a separate neutral, so you could not create a 120 volt outlet.
  • 4Wire Generator Plug
    If there were a 4-wire outlet then there would be the potential for 120/240 volts.
  • 120 Volt Portable Power From a 4Wire Outlet of a Portable Power
    From a 4wire outlet, the appropriate generator cord sized for the potential amperage rating of the outlet could be connected to a NEMA 3R panel which could provide the needed 120 volt circuits with would be provided through the appropriate over current protection or circuit breaker.

    • IMPORTANT: Outdoor electrical outlets should always have GFCI protection.
  • Connecting a Portable Generator to a Home Panel
    Connecting a portable generator to a home must always be done through an approved transfer switch or circuit interlock device to ensure power separation between the electric utility company and the portable generator.

More about Wiring Generators

  • Portable Home Generators
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