# How to calculate connected electrical loads

Written by michael logan
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Calculating connected electrical loads is important to prevent blowing fuses or tripping circuit breakers, since this usually happens when the circuit is overloaded. An electrical load is how much current a device draws when it is operating. Current is expressed in amperes and power is expressed in watts or kilowatts. Power (P) is calculated from voltage (V) and current (I) where P= I x V. You can calculate current from power by a similar formulas where I = P / V.

Skill level:
Moderate

## Instructions

1. 1

Find the current draw of each device on a circuit. Some devices like a vacuum cleaner will have the current requirements stamped on them. Other devices like a hair dryer may show how much power they use in watts or volt-amps, such a blow dryer for hair or an electric light bulb. Record the power or current requirements of each device on paper.

2. 2

Convert the power or current requirements recorded for all devices to amperes. Divide watts or volt-amps by volts to get amperes. Most receptacles in a house provide 120 volts while electric ranges and electric dryers usually 240 volts. If a device gives the current requirements as Milli-amps or Ma, simply divide by 1000 to get amperes. 500 Milli-amps = 0.5 amperes.

3. 3

Add up the current requirements in amps for all the devices connected to a circuit. The resulting number is the total connected load for the circuit, expressed in amperes.

#### Tips and warnings

• If you have a clamp style ammeter, you can measure the load of a device that does not list its current requirements for power usage.

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