Calculating Circuit Load

• Finding an Electrical Source
• Fishing Wiring in Walls
• Wiring Behind Baseboards
• Add a New Ceiling Fixture

An overloaded circuit can heat up to extreme temperatures creating a serious fire hazard to life and property. To protect against overload always know how much current is drawn on a circuit before adding a new outlet. To determine the load or amps drawn on a circuit, add the load of all the devices on the circuit.

First, to determine which electrical appliances are plugged into a circuit, turn off the circuit breaker and count all the devices that stop working. Add the amps drawn by each device. The total should not exceed 80% of the amp rating printed on the circuit breaker. For example, a circuit with a ceiling fan, TV and two floor lamps with 60 watt bulbs adds up to 5.58 amps if all these devices are running at the highest speed, all at the same time. This is 35% of the available capacity for a 15 amp/120 volt circuit, making this circuit a good candidate for adding a new electrical outlet.

To find the amps drawn by a device first look for a label with this information on it. If a label isn't available you can calculate the load amperage by dividing the wattage rating for the device by the voltage of the circuit or:

(Device Wattage / Circuit Voltage = Amps Drawn)

Wattage Rating for Common Household Appliances

Below is a chart of common household appliances and the average wattage ratings for each to aid in calculating the load of a circuit.