ELECTRICAL SYSTEMS-HOUSE - 8
148
CAY M A N 2 0 0 7
WARNING:
The 120/240 Volt AC panels contain
high voltage which can cause serious
injury or death. Before beginning any
work or testing procedures involving
the electric panels, or any of the branch
circuits, be sure the motorhome is
unplugged from shore power, the
generator is not running and the
inverter is in the off position. Certain
testing procedures may require the
AC power to be on. Only qualified
personnel with electrical backgrounds
should attempt any testing procedures.
Circuit Breaker
The internal con guration of the circuit
breaker is designed to trip when excess
current causes the breaker to heat up. The trip
action of the circuit breaker can occur within
milliseconds. Breakers are designed to operate
at a continuous load of 80% of the breaker’s
rated capacity.
For example: A breaker with a 20 Amp
rating will operate a continuous 16 Amp load.
This design leaves a small amount of working
capacity within the breaker. When an inductive
load is applied, such as when an electric motor
turns on, the motor starts to spin and 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 decrease.
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, such as
air conditioners. When using outlets, care should
be considered when applying loads such as
electric motors, heaters, coffee makers, toasters,
hair dryers or other large current consuming
loads. The current rating is usually stated on
most electrical items. The current rating will
either be rated in amps or watts. Current ratings
stated on electrical items will change slightly
with voltage uctuations. 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 ne in one location but
problematic in another.
NOTE:
To calculate watts to amps, 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
AC which equals 11.913 Amps. Use this
formula to calculate the amount of load
and compare to the available power supply.
GFCI Breakers & Outlets
A Ground Fault Circuit
Interrupter (GFCI) can be
found in two different types
of applications. One type is
incorporated in a breaker used in
120 Volt AC breaker panels; the
other is incorporated in an outlet.
The GFCI, whether it is a
breaker or an outlet, offers two
types of protection. One type of
protection is from over-current or
shorts to guard against hazardous
ground fault currents that can
result in injury or death. Ground
fault currents are currents that ow
from the “hot” or power terminal
through a person to the ground.
For example: touching a faulty
appliance while making contact
with an electrical ground such as a
water xture or the earth.
The GFCI offers protection
against the type of shock that can
result from faulty insulation, wet
wiring from inside an appliance, or any device
or equipment plugged in or wired to that circuit.
The ground fault portion of the outlet or breaker
uses sensitive electronics inside the outlet or
breaker to detect a ground fault problem. The
electronics monitor the normal current of power
owing to the hot (black) wire through the load
(eg. a light bulb or appliance) and coming back
on the neutral (white) wire. If a small amount of
current comes back on the safety ground wire,
the electronics will trip the breaker or outlet,
stopping the ow of electricity.
GFCI Breaker
RM03A0003
060072
ENCLOSED ENERGY MANAGEMENT EQUIPMENT
Typical Main Panel
060101b
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