How to Install and Wire a Sub-Panel
By Dave Rongey
Summary: Electrical Sub-Panel wiring considerations for the home complete with pictures. Careful planning for your Sub-Panel with immediate and future load considerations will help you understand how to size your Sub-Panel. This information will help as you consider a Sub-Panel and its size.
How to Install and Wire a Sub-Panel the Right Way
Make a List of all the things you plan to use
120 volt devices
Electrical Convenience Outlets
GFCI Protected Outlets
240 volt equipment
Hot Tubs [see the Hot Tub Page]
Correct amperage for all existing loads and future requirements.
Considerations to help determine Sub-Panel Circuit Requirements:
Important Factor: Find out if the Main Service or the Panel that will supply the Sub-Panel Circuit have adequate Load Capacity and space for the needed circuit breaker.
How big should your Sub-Panel be ? (Watts and Amperage)
This will help you consider the circuits to be served by the Sub-Panel including general purpose electrical outlets and any special equipment which will be needed.
Large 220 Volt Loads such as Welders, Air Conditioners, Motors, Well Pumps and the like may require larger size wire and conduit to provide the necessary current this equipment requires. Be sure to list all the label requirements and manufacturers specifications.
Long Distances from the power source will produce Voltage Drop, especially over 175 feet. A 2% Voltage drop factor and correction will most likely require an increased size of the wire and conduit.
Wire Types and Capacities
Cables and common wire types
Devices and Junction Boxes
Select the right box for your application
120/240 Volt Sub-Panel Circuit Requirements
4-Wire System consisting of:
2-Insulated Power Conductors (Black & Red)
1-Insulated Neutral Conductor (White)
(Bare or Green)
Don't Make This Mistake!
[click pictures to enlarge]
More about Wiring a Sub Panel
- Grounds and Neutrals in Electrical Panel
- How to Wire Grounds and Neutrals in Sub Panels – all the neutrals and ground wire and terminal bars must be separated from each other, and your sub feed should be a 4-wire cable that has a separated insulated neutral wire and a separate ground wire.
- Sub Panel Grounding and Neutrals
- Understanding Grounding for Sub Panels: When you add a second electrical panel with separate neutral and common bars, do you ground the common to the box along with a ground rod connection?
- How to Install a Sub Panel for an Attached Garage
- Planning and Installing a Garage Sub Panel: Do This Before Installing a Garage Electrical Panel, Check the Main Panel, Select the Wire Type and Wiring Method, Check the Wiring Path, Outlets and GFCI Requirements, Electrical Code Compliance.
- Considerations When Planning An Electrical Sub Panel
- How to Plan for a Sub Panel Installation: Planning the right amperage and cabling for a sub-panel used in a basement, garage and other locations.
- How to Plan for a Sub Panel
- Planning for an Electric Sub Panel: Identifying Panel Circuits and Connected Loads. Sub Panels are installed and used for several reasons including expanding the circuit breaker capacity of the main electrical panel.
Questions about Sub-Panels
Questions about Wiring Panels
Let Us Hear Your Question!
You Can Avoid Costly Mistakes!
Here's How to Do It:
Wire It Right with the help of my Illustrated Wiring Book
Great for any Home Wiring Project.
See How to Wire it Right!
The Safest Way to Test Electrical Devices and Identify Electric Wiring!
The Non-Contact Electrical Tester
This is a testing tool that I have had in my personal electrical tool pouch for years, and is the first test tool I grab to help identify electrical wiring. It is a Non-contact tester, [amazon.com], I use for the detection of Standard Voltage in Cables, Cords, Circuit Breakers, Lighting Fixtures, Switches, Outlets and Wires. Simply insert the end of the tester into an outlet, lamp socket, or hold the end of the tester against the wire you wish to test. Very handy and easy to use.