The best way to define a subpanel is to describe what it is not. A subpanel is not a service panel (often called a main panel), which is the first panel after the electric meter and is capable of shutting off all the incoming power to it. A subpanel is downstream from the service panel and electricity flows through a circuit breaker in the service panel to get to it.
A service panel can have multiple subpanels, each of which may be used to control power in different areas of a building or nearby buildings. And a subpanel can have other subpanels downstream from it. Also, a subpanel may have a main breaker inside that disconnects all power from it; but that is not required, because it can be accomplished by its breaker in the service panel. And a subpanel must be wired a little differently from a service panel, with neutral wires connected to a separate bus that is not bonded with the ground wires.
Although a subpanel might be smaller, like the one shown above, it can also be large, with dozens of circuits. Many homes today have a service panel at an outside wall, and the panel inside the house with most of the circuit breakers is a subpanel.
To learn more about subpanels, see our articles Why is it unsafe to bond neutral and ground wiring at subpanels? and Why is there no main shut-off breaker in my electric panel? and What is the main bonding jumper and where do it find it in an electric panel?
• • • • • • • • • • • • • • • • • • • • • • • • • •
Here’s links to a collection of our other blog posts about ELECTRIC PANELS:
• What causes copper wires to turn green or black in an electric panel?
• What is a split bus electric panel?
• What is the maximum number of circuit breakers allowed in an electric panel?
• When should a corroded or damaged electric panel cabinet or disconnect box be replaced?
• What is a tandem circuit breaker?
• When did arc fault circuit interrupter (AFCI) breakers first become required?
• Can an electric panel be located in a closet?
• Can an electric panel be located in a bathroom?
• Can you add circuit breakers by different manufacturers to an electric panel if they fit?
• My circuit breaker won't reset. What's wrong?
• What does a circuit breaker with a yellow or white test button indicate?
• What is the maximum gap allowed between the front of a recessed electric panel box and the wall surface surrounding it?
• What are the requirements for NM-cables entering an electric panel box?
• Why is a fuse box/panel an insurance problem for homebuyers?
• Why is bundled wiring in an electric panel a defect?
• What is the difference between GFCI and AFCI circuit breakers?
• Why are old electrical components not always "grandfathered" as acceptable by home inspectors?
• What happens when you press the "TEST" button on a circuit breaker in an electric panel?
• What is a Dual Function Circuit Interrupter (DFCI)?
• What is the difference between a Combination Arc Fault Circuit Interrupter (CAFCI) and an Arc Fault Circuit Interrupter (AFCI) circuit breaker?
• Why do some breakers in my electric panel have a "TEST" button on them?
• What is the right size electric panel for a house?
• What do I need to know about buying a whole house surge protector?
• What is the code required clearance in front of an electric panel?
• What is the difference between "grounded" and "grounding" electrical conductors?
• What does it mean when a wire is "overstripped" at a circuit breaker?
• Why is an old fuse panel dangerous?
• Who is the manufacturer of those "bad" electric panels?
• Why is the circuit breaker stuck in the middle?
• What is a double tap at a circuit breaker?
• What is the right electric wire size for a circuit breaker in an electric panel?
• What is the life expectancy of a circuit breaker?
Visit our ELECTRIC PANELS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.