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How to Install a Subpanel

Add more power, convenience, and safety to your house's electrical system
with Brian Walo

Whether you're building an addition or renovating an existing space, a new subpanel may be the easiest way to add electrical circuits to a house. In this For Pros By Pros video series, licenced electrician Brian Walo shows you everything you will need to do the job right.

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Attic-Insulation Upgrade Download the Article:
Subpanels Bring Big Amps to Distant Spaces

Online Members can read this related article from Fine Homebuilding magazine.

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A Subpanel is a Secondary Breaker Box

Instead of originating at the main service panel, electrical circuits can begin at a nearby subpanel that is powered from the main panel through one heavy-gauge cable. This configuration saves wiring, energy and your footsteps to a distant panel to reset a tripped breaker.

Subpanels can update old electrical systems
Adding a subpanel is sometimes the best way to integrate new wiring with an old electrical system. In the article Wiring a Master Suite Addition, a new subpanel was installed to replace an old, failing subpanel in a poor location. The article lists some other circumstances where a subpanel can save the day:

  • If the main panel doesn’t have enough open breaker spaces for the new circuits
  • When AFCI breakers aren’t available for an older electrical panel
  • If it’s a long way from the new wiring to the main panel
  • Pulling one feeder cable would be more convenient than pulling several branch-circuit cables
  • If you expect to need more circuits in the same part of the house in the future




Self-draining Sill Pans Fitting and Fastening the Box

See how to measure and mark the location of your new subpanel, and attach it firmly to your wall.

Sill Pan Flashing Options Running the Main Power Feed

Learn how to run the main feed cable into the box. Also, get some tips on measuring and maneuvering large-gauge cables in a tight space.
Sill Pan With Regular Peel-and-Stick Installing Circuits and Breakers

See how to run wires, install breakers, and make all the connections in the subpanel. Plus, learn an easy to organize and label your circuits.
Sill Pan With Regular Peel-and-Stick Subpanel Safety Tips (FREE)

Working in any electrical panel can be extremely dangerous. Find out what precautions to take when installing your subpanel.


FURTHER RESOURCES ON FineHomebuilding.com

Snake wire with a tape measureVIDEO: Snake Wire With an Old Tape Measure
 A tape with a missing hook is great for getting between insulation and drywall.

Ten Common Wiring Problems
Frequently found mistakes that could cost you your house or your life used to

existing_subpanel.jpgInstalling a Circuit Breaker in an Existing Panel
When adding a new circuit or replacing a faulty breaker, here is what you need to know to work safely in the panel

An Electrical Tool Kit
Essential tools and materials for the most common wiring tasks

new-wires-old-walls.jpg Running New Wires through Old Walls
With an assortment of tools, a few tricks, and a little luck, you can make electrical cable go where you didn't think it could

The Inspector Game:
Inspect an Electrical Panel
Help tie up five loose ends in this sloppy electrical service installation.

Brian Walo

Brian Walo
Brian Walo is a licensed electrician in Mount Pleasant, SC. When he’s not designing additions or renovations, he enjoys fishing, working on handmade guitars and furniture, and honing his culinary skills. Brian lives with his wife, Val, and their daughter, Grace.




WIRING-A-HOUSE.JPGWIRING A HOUSE

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