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Ask an Expert: Is it Dangerous to Overload a Circuit?

An expert explains the dangers of excess demand placed on electrical circuits.


Photo of several cords plugged into multiple power strips.
Too much demand on a circuit can risk a fire or other safety hazard.

How many electrical cords can I plug into a circuit?

Overloaded electrical circuits are more common than you might think. Overloads occur when more electrical demand is placed on a circuit than it can handle. Circuit overloads can cause nuisance tripping of breakers, a fire, or other serious safety hazards. Easy and inexpensive short-term solutions are tempting, but they can put your organization at risk. By understanding the causes of circuit overloads and how to prevent them, you can help ensure the safety of your staff and facility.


The lowdown on overloads

Wires in an electrical system or circuit have a maximum amount of current they can safely carry. If too many devices are plugged into a circuit, the electrical current will heat the wires to a very high temperature. If any one device uses too much current, the wires will heat up. The temperature of the wires can be high enough to cause a fire. If their insulation melts, arcing may occur, which can also cause a fire. The National Electrical Code Table 310.15(B) gives maximum amperage for various wire sizes at different temperature ratings.


To prevent too much current, a circuit breaker or fuse is placed in the circuit. If there is too much current in the circuit, the breaker "trips" and opens like a switch. If an overloaded circuit is equipped with a fuse, an internal part of the fuse melts, opening the circuit. Both breakers and fuses do the same thing: open the circuit to shut off the electrical current. If any other device is powered by the same wiring, a larger wire gauge would have to be used.


If the breakers or fuses are too big for the wires they are supposed to protect, an overload in the circuit will not be detected and the current will not be shut off. Overloading leads to overheating of circuit components—including wires—and may cause a fire. A circuit with improper overcurrent protection devices, or one with no overcurrent protection devices at all, is a fire and shock hazard.


Preventing circuit overloading

There are steps you can take to reduce the risk of circuit overloads in your home:

  • Get an inspection. If circuits are continually tripping or fuses are blowing, hire a qualified electrician to inspect the system. The inspection will determine your electrical needs and identify any necessary modifications to the system.

  • Replace fuses. The presence of fuses in your electrical system is a sign of older (and potentially hazardous) wiring. Consider replacing fuses with circuit breakers.

  • Check for loose connections or corroded wires. Circuit overloads can result from loose connections or corroded wires. These could be at the circuit panel, junction box, or anywhere in the electrical system. If you suspect a problem, contact a qualified electrician.

  • Keep temporary wiring temporary. Temporary wiring, such as extension cords and power strips, are not designed for long-term use. If this becomes the case, consider having additional outlets or electrical capacity installed.

  • Adding new equipment. The addition of new equipment can put a strain on your electric system and cause circuit overload. When adding new electrical devices or reconfiguring existing equipment, consult with a qualified electrician about installing additional capacity.

Ensuring your electrical system meets your needs can reduce the risk of fire or other safety hazards and eliminate costly or dangerous situations for your home and family.

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