How to Wire a Generator Cord

By Dave Rongey - Summary:

Should a generator cord have 3 or 4 wires? How to Wire a Cord for a Generator, Connecting a 3-Wire and 4-Wire Cord to a Generator, Generator Cord and Connector Amperage Ratings.

Wiring a Generator Cord

Electrical Question: Should a generator cord have 3 or 4 wires?

I am wiring a cord for my generator, would you suggest 3 conductor or 4 conductor cable?

My Generator Specifications

  • I have an older gas powered generator and it is rated at:
    • Voltage: 120/240.
    • Amps: 41.7/20.8.
    • Single Phase.
    • The outlets are one duplex NEMA 6-20R and one duplex of 5-20R.

My Generator Project

  • I want to split the 240V into 2@120V circuits. Looking at the wiring diagram of the 6-20R, I see 2 hot leads and 1 ground lead.
  • My guess is that I bond the neutral to the ground and so my wiring would be one hot and the neutral/ground to each new 5-20R.
  • So the result would be a ‘Y Pigtail’ with a 6-20P (240) and 5-20Rs on the other end.
  • Would you suggest 3 conductor or 4 conductor cable for the pigtail.

Thank you.

This electrical wiring question came from: Ray, from Costa Mesa, California.

Dave’s Reply:
Thanks for your electric wiring question Ray.

How to Wire a Cord for a Generator

wiring generator cord

Application: Wiring a Generator Cord.
Skill Level: Advanced – Best performed by a Licensed Electrical Contractor.
Tools Required: Electricians pouch of hand tools.
Estimated Time: Depends on the type and size of the generator output, the specific receptacle, and the available access to the project area.
Note: Generator power should always be wired through an approved transfer switch or circuit interlock device. Any part of the home electrical system must NEVER be back-fed using a cheater cord. Back-feeding is extremely hazardous for the home, the occupants and the electric utility company repairmen.
Important: Installing a generator and transfer switch must be well thought out and performed with a permit with all work being inspected.

Wiring a Generator Cord

  • Generator power which will be used for multiple circuits should first connect to an electrical distribution panel.
  • A “Y” adapter should not be connected to a generator.
  • If the generator has a 3-wire receptacle which states that it is 240 volts then a separate  neutral is not present, therefore a 120 volt circuit is not available.
  • You can only obtain 120 volts from the receptacle which states that it is 120 volts.

Connecting a 3-Wire and 4-Wire Cord to a Generator

  • If the receptacle on the generator is a 3-wire type then a 3-wire cord and male connector body should be used.
  • If the generator receptacle is a 4-wire type then a 4-wire cord and male connector body should be used.

Generator Cord and Connector Amperage Ratings

  • Generator Receptacle Outlet Examples:
    • A NEMA 20R receptacle  indicates a 20 amp receptacle.
    • A NEMA 30R receptacle indicates a 30 amp receptacle.

Home Generator Cords

  • The connecting cord to the generator should be connected to a transfer switch, generator circuit panel, or an approved interlock device which is properly sized which will ensure that only one source of power is connected and ON at any given time.

More about Home Generators

Home Electric Generators

  • Home 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 Transfer Switches are the Safe Link To Powering Your Home

The Generator Transfer Switch

  • See how a transfer switch ensures a safe isolation of the electric utility company and your home generator.


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