What Size Main Disconnect Breaker in a Sub Panel

Can I use a 100amp main breaker in a 50amp sub panel? Options for a Main Disconnect Breaker in a Sub Panel. © By: Dave Rongey

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Main Breaker for a Sub Panel
Electrical Question: Can I use a 100amp main breaker in a 50amp sub panel?

Wiring a Sub Panel

Bruce asks:
If I choose to use a panel that has a breaker factory installed which you can not change because I would like a disconnect in my sub panel and the breaker in that panel is 100 amps the lowest you can buy, can I use this breaker if I install a 50 amp sub panel with the proper feed wire for a 50 amp sub panel? I am told that this breaker would be the means of disconnect only.

Additional Comments: Great site

Dave’s Reply:

Thanks for your electrical wiring question Bruce.

Main Disconnect Breaker for a Sub Panel

Application: Installing a Sub Panel.
Skill Level: Advanced – Best performed by a Licensed Electrical Contractor, or Certified Electrician.
Electrical Tools Required: Basic Electricians Pouch Hand Tools, Voltage Tester, and appropriate Safety Gear.
Estimated Time: Depends on the personal level experience, ability to work with tools, install electrical circuit wiring, and the available access to the project area.
Electrical Safety: Identify the electrical power source to the Sub Panel, turn it OFF and Tag with a Note before working with the electrical wiring.
Electrical Wiring Parts and Materials: Electrical parts and materials for the Sub Panel should be approved for the specific project and compliant with local and national electrical codes.
Electrical Codes and Inspections: Installing or changing home electrical wiring should be done according to local and national electrical codes as adopted in your specific area. A permit and inspections may also be required.

Installing a Sub Panel in a Basement

This electrical wiring project is about Residential Electrical Code a Sub Panel in the Basement of a Old Home.

Options for a Main Disconnect Breaker in a Sub Panel

• Bruce, from the information you have provided, a 50amp rated cable feed must be protected by a 50amp circuit breaker at the panel that is the source of power.
• I personally have never used a circuit breaker in a sub panel that is rated at a higher amperage than the amperage rating of the cable feed to the sub panel.
• In many cases, the factory installed circuit breaker may be replaced with a breaker that has a lower amperage rating, however if this is not possible, then a sub panel may be installed that does not have a factor installed main breaker, and a 2pole breaker with the correct amperage rating for the supply cable may be installed and labeled as the main breaker, which in turn will then be the main disconnect for the sub panel.

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