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Grounded Electrical Power Distribution System
The
N
ational
E
lectrical
C
ode (NEC) requires the use of a “grounded electrical
distribution system”. As per this system, one of the two current-carrying conductors
is required to be grounded. This grounded conductor is called the “Neutral / Cold /
Return”. As this conductor is bonded to earth ground, it will be at near zero voltage
or potential. There is no risk of electrical shock if this conductor is touched. The
other current carrying conductor is called the “Line / Live / Hot”. The connection
between the “Neutral” and the grounding electrode conductor is made
only at one
point in the system
. This is known as the
system ground
. This single point connection
(bond) is usually made in the service entrance or the load center. If this connection is
inadvertently made in more than one place, then unwanted currents will flow in the
equipment grounding conductors. These unwanted currents may cause inverters and
charge controllers to be unreliable and may interfere with the operation of ground-
fault detectors and over-current devices.
NOTE: A current-carrying conductor that is not bonded to the earth ground cannot be
called a “neutral”. This conductor will be at an elevated voltage with respect to the
earth ground and may produce electrical shock when touched.
Polarity and color codes for power cords and plugs for AC devices and appliances
Single phase 120 VAC, 60 Hz AC devices and appliances use 2 pole, 3 wire grounding
configuration for connection to the AC power source. The plug of the power cord has
three pins – two flat pins ( also called poles ) that are connected to the two current-
carrying conductors and a round pin which is connected to a non-current carrying
conductor ( this will carry current only during ground fault conditions ) . One flat pin
is connected to a black current-carrying conductor which is also called “Line/Live/Hot”
pole. The other flat pin is connected to the white current-carrying conductor also
called the “Neutral / Return / Cold” pole. The third round pin is connected to the non-
current carrying green “equipment grounding conductor”. This green “equipment
grounding conductor” is bonded to the metal chassis of the device or appliance.
AC output connections
The 120 VAC, 60 Hz version of the inverter uses NEMA 5-15R receptacles for
connecting the AC output of the inverter to devices and appliances fitted with a
NEMA 5-15P plug. The two rectangular slots are connected to the current-carrying
conductors of the AC power source inside the inverter. The round slot is the
“equipment grounding” connection and is internally connected to the metal chassis of
the inverter.
CAUTION! :
For the 120 VAC, 60 Hz NEMA 5-15R receptacle used in this inverter, the
current carrying conductor connected to the longer rectangular slot is isolated from
the metal chassis of the inverter. Hence, when the metal chassis of the inverter is
connected to the earth ground, the longer rectangular slot is not grounded to the
earth ground. The longer rectangular slot is, therefore, not a “neutral”. Do not touch
this slot as it will be at an elevated voltage with respect to the metal chassis / earth
ground and may produce an electrical shock when touched.
