Timothy Thiele holds an associate degree in electronics and is a member of IBEW Local #176. He brings more than three decades of expertise in wiring for residential, commercial, and industrial projects.
If you’ve ever connected too many holiday lights, turned on a vacuum, or increased the heat on a space heater, only to have the lights or appliance cut out unexpectedly, you’ve experienced an electrical circuit overload. This interruption was caused by the circuit breaker or fuses in your home’s electrical panel. Although circuit breakers are dependable and effectively reduce the risk of house fires caused by overloads, the best approach is to monitor your electricity consumption to avoid overloads altogether.
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What does it mean when an electrical circuit is overloaded?
An electrical circuit overload happens when the amount of electricity being used exceeds the safe capacity of the circuit.
What Causes Electrical Circuit Overloads?
Electrical circuits are engineered to accommodate a specific amount of electrical current. These circuits consist of wiring, a circuit breaker (or a fuse in older systems), and various devices, including light fixtures, appliances, and anything connected to an outlet. The electrical consumption of each device in operation contributes to the overall load on the circuit. If the load surpasses the circuit’s rated capacity, the circuit breaker will activate, cutting off the power to the entire circuit.
In the absence of a circuit breaker, an overload could result in the overheating of the circuit wiring, potentially melting the insulation of the wires and creating a fire hazard. Various circuits are rated for different loads, meaning some can handle more electricity than others. While residential electrical systems are typically designed for standard household consumption, there are no restrictions on connecting multiple devices to the same circuit. Understanding the configuration of your home’s circuits can significantly help in avoiding overload situations.
Indicators of Circuit Overload
A clear indication of an overloaded electrical circuit is when a circuit breaker trips, cutting off the power supply. However, there are also subtler signs that may not be as easily recognized:
- Flickering lights, particularly when they dim upon activating appliances or additional lighting.
- Humming electrical sockets or switches.
- Outlet or switch plates that feel warm when touched.
- Foul smells emanating from electrical outlets or switches.
- Burnt sockets or plugs.
- Power tools, appliances, or electronic devices that appear to have inadequate power.
Noisy buzzing, the scent of burning, and devices that feel unusually hot may signal additional wiring issues, like loose connections or short circuits. If these issues continue despite your efforts to avoid circuit overloads, it’s advisable to reach out to an electrician.
Creating a Diagram of Your Home’s Electrical Circuits
To avoid overloading electrical circuits, the initial step is to identify which circuits are connected to which appliances. Once you have a clear understanding of the circuit configuration, you can determine the safe load capacity of each circuit, allowing you to gauge how many devices can be used simultaneously. For instance, if the lights in your kitchen dim when you activate your toaster oven, a high-energy device, it indicates that both the toaster and the lights are sharing the same circuit, which is not ideal, and that you are nearing the circuit’s load limit. Additionally, analyzing the circuit layout can reveal whether there is a need to install new circuits to accommodate the typical electrical demands of your home.
Mapping electrical circuits is straightforward (though it may be repetitive): Grab a notepad and a pencil. Open the door to your home’s service panel (breaker box) and switch off one of the breakers labeled with the numbers 15 or 20. (Avoid the breakers labeled with 30, 40, 50, or higher, as these are high-voltage circuits intended for appliances such as electric stoves, water heaters, and dryers, and are not for standard appliances.) Make a note on your pad indicating the position of the circuit within the panel for future reference.
Next, take a tour of the house and check all the lights, ceiling fans, and plugged-in devices. Make a note of anything that isn’t functioning and the specific room it’s located in. Additionally, use a voltage tester, receptacle tester, or a plug-in light or lamp to check each outlet, documenting any that are not operational. You don’t need to inspect the entire house for each circuit. If your electrician did a thorough job, there might be useful labels next to the breakers that indicate the circuit areas, such as “Southeast bedroom” or “Garage lights.” However, for a precise mapping, it’s advisable to test each area comprehensively, as circuits can sometimes include unexpected devices, like a microwave connected to a hallway lighting circuit.
Once you have assessed the circuit area, return to the panel, activate the first breaker, then deactivate the subsequent one in the sequence, and conduct the test again. Continue this procedure for all the circuits labeled “15” and “20.”
Determining Electrical Circuit Loads
The circuit diagram indicates which devices are connected to each circuit. Next, you need to determine the power consumption of these devices. For this, a brief overview of electrical energy is necessary. Electricity is quantified in wattsfor instance, a 100-watt light bulb consumes 100 watts of power. A watt is calculated by multiplying voltage (volts) by current (amps):
1 volt multiplied by 1 amp equals 1 watt.
To determine the overall load on each circuit, sum the wattage of every device connected to it. Light bulbs and numerous small appliances typically display their wattage on their labels. For devices that only provide their amperage, convert the amp rating to wattage by multiplying it by 120, which is the standard circuit voltage. Make sure to account for all devices that are hardwired to the circuit, as well as any plug-in appliances that are rarely relocated, such as a toaster oven or a heater in a particularly chilly room.
Evaluate the overall wattage of each circuit against its load capacity. Circuits equipped with 15 breakers have a capacity of 15 amps. The highest load capacity for these circuits is 1,800 watts.
120 volts multiplied by 15 amps equals 1,800 watts.
Exceeding 1,800 watts on that circuit will cause an overload, resulting in the breaker tripping.
The circuits equipped with 20 breakers are designed to handle 20 amps and can support a maximum load of 2,400 watts.
120 volts multiplied by 20 amps equals 2,400 watts.
Evaluate the total wattage being consumed against the load capacity of each circuit. For instance, a 15-amp circuit that powers lighting and outlets in a living room may supply 500 watts for the lights, 500 watts for the television and cable box, and 200 watts for the audio system, resulting in a total of 1,200 watts. If a 700-watt vacuum cleaner is plugged in while the television, stereo, and lights are in use, the total will surpass the 1,500-watt limit of the circuit breaker, leading to a trip and a loss of power.
Solutions
The optimal goal for each circuit should not be the maximum load capacity. To ensure safety, it is advisable that the typical load on a circuit remains below 80 percent of its maximum (rated) capacity. For a circuit rated at 15 amps, the recommended safe load is 1,440 watts, while for a 20-amp circuit, the safe load is 1,920 watts.
If your circuit analysis shows that the wattage being drawn exceeds the safe load limit, or if you are consistently overloading the circuit beyond its rated capacity, there are several strategies you can implement to decrease the load and avoid overloading the circuit:
- Relocate plug-in devices to a circuit that experiences lower usage (utilize your circuit mapping and calculations to pinpoint circuits with ample available wattage).
- Be mindful not to activate multiple devices simultaneously. For instance, switch off the television and audio system while you’re vacuuming, as you won’t be able to hear them regardless.
- Lower energy consumption by swapping out incandescent or halogen bulbs for energy-efficient LED bulbs or, if necessary, CFL (compact fluorescent) bulbs.
- Set up additional circuits for devices that require a significant amount of power. For instance, if you frequently use power tools in your garage workshop and your current wiring has all outlets and lighting connected to a single 15-amp circuit, consider adding a new 20-amp circuit to provide several new outlets for your tools.
