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How to Convert a Circuit to be Used for a Sub-Panel


By Dave Rongey - Summary:

Converting a 220 Volt Circuit Cable for a Sub-Panel: How to Install a Sub Panel Using an Existing Circuit, Sub Panels Require a 4-Wire Feeder Cable with a Separate Dedicated Neutral.


Converting a 220 Volt Circuit Cable for a Sub-Panel

Electrical Question: I have an old 220 volt circuit that went to an electric range.

  • We have since switched to N.G.
  • My question is can I reroute the 220 volt cable to the basement and use it for the power to a sub-panel?
  • I only have one receptacle in the basement.

Thanks for the info.

This electrical wiring question came from: Buck, from Emmett, Idaho.
See more about Home Wiring for Idaho

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

How to Install a Sub Panel Using an Existing Circuit

Skill Level: Intermediate to Advanced – Best performed by a licensed electrician.
Tools Required: Electricians pouch of hand tools and the various power tools necessary for installing the sub-panel.
Estimated Time: Depends on the type and size of the panel and available access to the project area.
Precaution: Any existing electrical wiring within the immediate area that may interfere with the installation of the sub panel should be identified and turned OFF and Tagged if necessary.
Notice: Installing additional electrical wiring and a sub-panel should be done according to local and national electrical codes with a permit and be inspected.

Sub Panels Require a 4-Wire Feeder Cable with a Separate Dedicated Neutral

  • 120/240 Volt Circuits
  • A typical sub panel that will be used to supply power for 120 volt circuits.
  • Typical 120 volt circuits may be receptacle outlets, lighting, smoke detectors, or any other 3-wire 120 volt device.

Circuit Disconnect for 240 Volt Equipment

  • 240 Volt Circuits
  • A Dedicated Neutral wire conductor is not required for 240 volt circuits for equipment that does not require a neutral.
  • Typical 240 volt equipment may be a hot water heater, air compressor, welder, or any 3-wire 240 volt equipment.
  • The circuit amperage requirements must be within the range of the amperage rating of the cable to be used for the circuit.

IMPORTANT:
The total connected load of the circuits that would be added to a sub-panel must be 80% of the amperage rating of the cable supplying power to the sub-panel.

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FAQs Frequently Asked Questions and Comments

2 Responses to “How to Convert a Circuit to be Used for a Sub-Panel”
  1. Chuck1963 says:

    We have a 220 volt dryer service that we are not using . I am setting up a wood shop in the same building ,can I split the 220 volt service in to a sub panel box & supply my wood working tools with 110 volts ?

    • Dave Rongey says:

      Hi Chuck,
      If the 220 volt dryer circuit is a 3-wire with a ground then yes you can use the circuit for a sub feed. The 3-wire circuit will have a separate insulated white neutral wire which is required for 120 volt circuits.
      If the 220 volt circuit does not have a separate neutral wire then no, you cannot use the circuit for a sub panel.
      Dave


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