Used Breakers 101: A Guide to Troubleshooting Circuit Breakers


An electric circuit breaker is an important part of any electrical wiring system. It is designed to interrupt the flow of electricity the moment a fault, such as an overload or short circuit, occurs. Circuit breakers are made in a variety of sizes, depending on the area they cover. As a homeowner, it is important to know about some common electric circuit breaker problems and their solutions.


Circuit Overload

A circuit can become overloaded when more current (amps) runs through the circuit than it was designed to handle safely. Overloads can be caused by operating too many devices on one circuit, a malfunctioning appliance or by loose or corroded wires or connections.

Circuit breakers come in different amperage ratings that determine how much current can safely flow through the circuit. If a 15 Amp circuit breaker is protecting a series of receptacles with various devices plugged in, like a hair dryer, computer and television, the circuit breaker will trip if the current exceeds 15 Amps. This prevents overheating, which can cause a fire.

In the case of a breaker trip where overload is suspected, unplug all the items on the circuit before resetting the breaker.  After it is reset, turn on the devices, one at a time, to determine what may have caused the overload.  If a circuit overload happens on a regular basis, a new dedicated circuit may need to be installed to handle the amperage load.




Testing for an Overload with a Clamp Meter

First, carefully remove the cover of the electrical panel and inspect inside for loose or damaged wires. The “hot” wires are usually black or red, the “neutral” wires are usually white and the ground wires are bare copper. If no damage is observed, set the clamp meter to AC amps and clamp it around the “hot” wire connected to the tripped breaker. Make sure all the lights or appliances you usually have on the circuit are turned on. Reset the breaker. If the reading on the clamp meter is higher than the rating on the breaker, then you have an overload.

Most home circuit breakers are rated at 15, 20 or 30 amps. However, breakers are designed to trip above 80 percent of the rated load. Therefore, a reading on the meter somewhat lower than the rating of the breaker may still result in an overload. Ask an assistant to turn on additional appliances or lights, one at a time, while you monitor the clamp meter reading.


Correcting an Overloaded Circuit

The solution to an overload is to fix or replace any item that is not working properly and redistribute the load. Move some devices from the overloaded circuit to a different circuit.

Re-check the current draw on both circuits to make sure it is less than 80 % of the rated current for each circuit breaker. If you cannot find any common causes for the overload, call an electrician to have the problem fixed.


Short Circuit

A short circuit is a serious problem which can cause a breaker to trip. It occurs when the hot wire touches another hot wire or touches a neutral wire. A short can also happen when there is a break in the circuit wiring.

These can be difficult to troubleshoot since the short can be the wiring or in a device on the circuit. Whatever the cause, short circuits pose a significant risk of fire or electrical shock and should be fixed immediately.

To identify a short circuit, first unplug all electrical appliances, lamps and devices that draw electricity on the circuit. Reset the breaker. If the breaker does not trip, the problem is with one of the devices that was plugged into the circuit.

In most plug-in appliances and lamps, the short circuit is usually in the power cord.  If the breaker trips immediately, the short circuit could be in an outlet, a ceiling or wall fixture or the wiring.


Check for Short Circuit in Devices

Inspect all appliance power cords for damage or a melted appearance. Use the Ohms function of the clamp meter to check for a short in each device that was plugged into the circuit by testing for continuity between the plug blades. If you measure a low resistance of just a few ohms, the device is the likely cause of the short circuit.

A high resistance reading means the device is not likely the problem. After testing each device, plug it into the circuit to verify that the breaker doesn’t trip.


Short Circuit Inspection Wiring and Outlets

If the short circuit seems to be in the wiring:

  • Confirm that power is off to the outlets.
  • Check your outlets and plugs for a burning smell or black discoloration.
  • Remove the receptacle cover and check the wire insulation. If it is brittle, cracked or touching another wire, the ground wire or the box (metal), it may be the source.
  • Check each outlet and light fixture, then switch on the circuit for resistance between the hot and neutral wires and between the hot and ground wires. A low resistance will indicate the presence of a short circuit. Remove the ceiling fixtures and inspect the wiring inside.
  • If you can’t find a problem, contact an electrician as soon as possible.


Ground Fault

A ground fault occurs when a hot or active wire contacts the ground wire, a grounded portion of the junction box or a grounded area of an appliance. When contact is made between a hot and ground wire, high current rates occur at the circuit breaker, which can cause it to trip.

The National Electrical Code (NEC) requires some areas of the home (kitchens, bathrooms, outdoor areas and other areas) be protected by Ground Fault Circuit Interrupters (GFCI) to prevent electrical shocks and fires. Ground faults usually happen when equipment is damaged or defective and can pose a danger since live electrical parts may no longer be adequately protected from unintended contact.



Circuit Breaker Replacement

If the measures taken above do not solve the issue, the problem may be the circuit breaker. If it is worn out or defective, it can trip even when the current draw is below the rated capacity.

Replace the circuit breaker. Always replace a circuit breaker with one that has the same rating as the existing breaker. Replacing a breaker with one at a higher current rating will not adequately protect the wiring and may result in a fire.

Keep in mind that circuit breakers are safety devices for our protection when electrical malfunctions occur.  Although it may be frustrating when a circuit breaker trips, this action has served to protect us and our property.  When troubleshooting or dealing with home electrical repairs, always take safety very seriously and never attempt to inspect or repair anything that you aren’t certain is safe.

For more serious electrical problems or if you are unfamiliar with how to replace a circuit breaker, contact a licensed electrician to make the repairs.

This is a guest article by Carl Babb, a retired Electrical Engineer from Massachusetts who blogs about the Industry for He is passionate about Green Energy and Building practices. Now retired he enjoys writing, spending time with his grandchildren, and staying current (pun intended). For more from Carl visit the Relectric Blog.

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