Installing an Electrical Sub-Panel
Thinking about installing a Sub Panel? Here is what must be considered first, and you may find that you really do not need a sub panel at all.
Guide for adding a Sub-Panel
Electrical Question #1: What is the best way to install a sub panel?
- I want to install a sub panel.
- Can I install a sub panel from another 100 amp main panel?
- What size wire cable should I use?
This electrical question came from: Barbaro, a Handyman in New Jersey.
Electrical Question #2: Can I add a sub panel to a sub panel?
- My electrician was supposed to provide for three 220volt outlets in my garage sub panel, but he used all the available breaker space for other circuits.
- Now there is one 220volt outlet circuit with unconnected wires in the panel and no where to go.
- How can I get this one outlet wired up, without replacing the entire sub panel?
- Should I replace the sub panel it with a larger panel?
This electrical wiring question came from Jack in California.
Thanks for your electrical wiring questions.
Considerations for Installing an Electrical Sub-Panel
Application: How to Add a Sub Panel.
Skill Level: Advanced. This electrical wiring project is best performed by a Licensed Electrical Contractor, Not Recommended for Homeowners.
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. Working in an electric panel is dangerous due to arc flash hazards and the possibility of electric shock.
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.
Before Installing an Electrical Sub Panel
Many electrical panels allow tandem, twin or quad circuit breakers to be installed which will allow the installation of a few more circuits, so research the type of panel that you have to see if it will allow installing circuit breakers of these types.
- Before installing a sub panel the following should be considered:
- Does the existing electrical panel have enough electrical capacity for the additional load of the new sub-panel.
- Does the existing electrical panel have the physical space available for a circuit breaker that would feed the new sub-panel.
- The size of the sub panel and the cable size that is required for the new sub-panel will depend on the electrical load that will be connected to the new sub-panel.
Factors that Determine the Size of a Sub Panel
- List all the electrical devices that will be added to the panel.
- Identify any devices that require a dedicated circuit.
- Determine the number of spaces that will be required for circuit breakers in the new sub panel.
- Calculate the total connected electrical load that will be added to the sub panel.
- Using the total connected load and the number of required circuits, determine the amperage of the sub panel and total number of circuit breaker spaces that will be needed.
- NOTE: The amperage size of the sub panel may be less than the total connected load. The actual panel amperage may be factored upon the circuits and equipment that is connected to the sub panel.
Electrical Calculations and Decisions about Electrical Materials
The following resources will assist you when planning to ad a sub panel.
Online Electrical Load Calculator
Residential Electrical Load Calculator, Online and Interactive provides accurate panel load calculations.
- Calculating the Panel Load: Electrical Load Calculator
Online Wire Size Calculator
Basic electrical calculations of voltage drop and power factors help you understand the requirements for electrical projects and safe circuit wiring.
- Sizing Wire for a Panel: Voltage Drop Calculator
Electrical Project Guidelines
Electrical wiring projects guidelines necessary to follow for most any project you may choose to do. By following a few simple steps you will be considering the components necessary for a successful project.
- Successful Electrical Projects from Start to Finish: Electrical Projects Guidelines
More about Electric Panels and Circuit Breakers
An Illustrated Guide to Circuit Breakers Complete with Diagrams and Photos from an Expert.
Circuit Breaker Panel
The home circuit breaker panel contains several circuit breakers that are carefully installed by experienced electricians and electrical contractors.
House Wiring Circuits and Circuit Breakers
This article looks at common 120 volt and 240 volt house wiring circuits and the circuit breakers that are installed identifying the types and amperage sizes used in most homes.
Home Electrical Wiring
Home electrical wiring projects with pictures and wiring diagrams.
Be Careful and Be Safe - Never Work on Energized Circuits!
Consult your Local Building Department about Permits and Inspections for all Electric Wiring Projects.
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