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
Lighting
Electrical Convenience Outlets
GFCI Protected Outlets

240 volt equipment
Motor Loads:
Hot Tubs [see the Hot Tub Page]
Well Pumps
Air Conditioners
Sub-Panel Considerations-
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.

Special Considerations:
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)
1-Ground Conductor (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.

Learn more about wiring a sub panel

« Electric Panel Circuit Listing

Electrical Code Articles »

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!

Complete Guide to Home Electrical Wiring

Learn more about How to Wire Circuit Breakers and Panels
Perfect for Homeowners, Students and Electricians
Includes:
Home Electrical Circuit Breakers
120 Volt Circuits
240 Volt Circuits
Multi-Wired Circuits
Wiring Methods for Installing Electrical Circuit Wiring
Electrical Codes for Home Electrical Wiring
....and much more.
Be Sure to Get Your Copy!


	Electrical Wiring Book

Electrical Tips to Help You Wire it Right
	The Safest Way to Test Electrical Devices and Identify Electric Wires! 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 that I use to easily Detect 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.
	The Quickest Way to Check for Faulty Electrical Wiring! The Plug-In Outlet Tester This is the first tool I grab to troubleshoot a problem with outlet circuit wiring. This popular tester is also used by most inspectors to test for power and check the polarity of circuit wiring. It detects probable improper wiring conditions in standard 110-125 VAC outlets Provides 6 probable wiring conditions that are quick and easy to read for ultimate efficiency Lights indicate if wiring is correct and indicator light chart is included Tests standard 3-wire outlets UL Listed Light indicates if wiring is incorrect Very handy and easy to use.
	Strip Off Wire Insulation without Nicking and Damaging the Electric Wire! The Wire Stripper and Wire Cutter My absolute favorite wire stripping tool that I have had in my personal electrical tool pouch for years, and this is the tool I use to safely strip electrical wires. This handy tool has multiple uses: The wire gauges are shown on the side of the tool so you know which slot to use for stripping insulation. The end of the tool can be used to grip and bend wire which is handy for attaching wire onto the screw terminals of switches and outlets.. The wire stripper will work on both solid and stranded wire. This tool is Very Handy and Easy to Use.