An electrical panel is overcrowded if the jumbled maze of wires makes it impossible to follow the path of a wire from the breaker to where it exits the box. The panel shown above was so jammed with wiring that we had to push the dead front firmly against the top layer of wiring to close the panel. Not good…and not safe. 

    Filling a panel with too many tandem breakers (the kind that fit two circuits into a single slot, also called duplex or half-high breakers) is the thing that most often causes an overcrowded panel. Manufacturers specify how many tandem breakers are allowed to be installed in a panel, and where they should be located, in the wiring diagram sticker on the inside of the panel door. Newer panels have a lockout device that keeps half-highs from being installed where they are not allowed. But older panels don’t have that safety feature, and there are ways that it can be overridden even in a new panel. See our articles What is the maximum number of circuit breakers allowed in an electric panel? and What is a CTL breaker? for more on this.

    Other factors for overcrowding  include an original installation that wasn’t planned to minimize running wires from one side of the box to the other, excessive lengths of wire left in panel, and not stripping the sheathing away from NM-cables once they enter the panel box. Panels that have been reconfigured by a homeowner or handyman to connect to a generator panel are another example. We wish all the electrical panels could look like the professional job at right. Many start off life like it, but get added to again and again over the years, instead of installing a subpanel—which is our usual recommendation for repairing an overpacked panel.

    The National Electrical Code [NEC 312.8(A)] does have a standard for the maximum amount of wires allowed in wiring space of a panel: they cannot occupy more than 40% of the space cross-section, and the total of wires, splices, and taps cannot exceed 75%. Unfortunately, the problem is often not so much the cross-sectional area as the organization of the wiring in the panel.

    The addition of a “plug-on neutral," which provides a neutral bus bar under the breakers, is one feature in newer panels that reduces the amount of wires in the panel. To learn more about it, go to Why are there no neutral pigtails at the AFCI and GFCI breakers in the panel? 

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Here’s links to a collection of our other blog posts about ELECTRIC PANELS:

• How can I tell a main electrical panel from a subpanel?

• What causes copper wires to turn green or black 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 is a split bus electric panel?

• How do I identify a combination AFCI (CAFCI) circuit breaker? 

• 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 a Dual Function Circuit Interrupter (DFCI)? 

• 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 maximum allowed height of a circuit breaker (OCPD) above the floor?

• What is the maximum height you can mount an electric panel above the floor? 

• What is the code required clearance in front of an electric panel?

• What is the main bonding jumper and where do it find it in an electric panel? 

   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.