Power Output And Demand - Westinghouse WH10000DF User Manual

OPERATION

POWER OUTPUT AND DEMAND

120-Volt AC devices have two different electric power demands that must be taken into
consideration, namely the running power and the starting/peak power. Both are measured in
Watts (typically abbreviated as "W").
The steady state continuous load is the running power demand and this is often marked on the
device near its model number or serial number. Sometimes the device might only be marked with its
voltage (i.e. 120 V) and current draw (e.g. 6 Amp or 6 A), in which case the running power demand in
Watts can be obtained by multiplying the voltage times the current, e.g. 120 V × 20 A = 2,400 W.
Simple resistive 120-Volt AC devices such as incandescent bulbs, toasters, heaters, etc. have no
extra power demand when starting, and so their starting power demands are the same as their
running power demands.
More complex 120-Volt AC devices containing inductive or capacitive elements such as electric
motors have a momentary extra power demand when starting, which can be up to seven times the
running power demand or more. Manufacturers of such devices rarely publish this starting power
demand and so it's often necessary to estimate it. A rule of thumb for devices fitted with an electric
motor is to apply a starting power multiplier of 1.2 for small hand-held or portable devices and a
value of 3.5 for larger stationary devices. For example, a 900 W angle grinder can be assumed to
have a starting power demand of at least 1.2 × 900 W, which equals 1,080 W. Similarly, a 1,650 W
air compressor can be assumed to have a starting power demand of at least 3.5 × 1,650 W, which
equals 5,775 W.
To prevent overloading of the generator's 120-Volt AC system:
1. Add up the running power demand of all the 120-Volt AC devices that will be connected to the
generator at one time. This total must not be greater than the generator's specified running power
output.
2. Add up the running power demand again, but for the largest motor-driven device use the value
of its starting power demand instead of its running power demand. This total must not be greater
than the generator's specified starting power output.
3. The total running power demand of all the devices that will be connected to any one of the
generator's outlets must not exceed the generator's specified running power output or 3,700 W,
whichever is the lesser.
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