8 • 315
Electrical Systems
2004 • LaPalma
Breaker current ratings are current set points in which the breaker is
designed to operate. The internal configuration of the circuit breaker is
designed to trip when excess current is drawn through the breaker. The
breaker will heat up from the excess current causing the breaker to trip. The
trip action of the circuit breaker can occur within milliseconds due to the
speed at which electricity can travel. Breaker ratings are set to operate on a
continuous load at 80% of the breaker’s rated capacity. For example: A
breaker with a 20 Amp rating will handle a continuous load of 16 Amps.
This designed set point is when an inductive load is applied, such as when
an electric motor turns on. As the motor starts to spin current consumption
may momentarily exceed the rated capacity of the breaker. As the electric
motor comes up to operating speed the electric motor’s current consumption
will fall. The AC current load then falls back into the breaker’s rated 80% set
point. This electric principle should be kept in mind when using anything
other than 50 Amp shore service and using appliances with electric motors.
When using outlets care should be considered when applying loads such as
electric motors, heaters, coffee makers, toasters, hair dryer or other large
current consuming loads. If the current rating of a load is not known it is
usually stated on most electrical items. The rating will either be in amps or
watts. Current ratings stated on electrical items will change slightly with
voltage fluctuations. As voltage increases current consumption decreases.
As voltage decreases current consumption increases. This may explain why
in some instances items operated at borderline voltage to current tolerances
may seem fine in one location but problematic in another.
NOTE: To calculate watts to amps simply divide the watt
figure by the voltage of which the item operates from. For
example: The electrical item is rated at 1370 watts. Divide
that by the operating voltage of 115 Volts which equals
11.913 Amps. Use this formula to calculate load to current
supply ratio.
Circuit Breakers
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