LT
−
ISOG26
−
1
Issue 1 Print 2
6
Charles Industries, Ltd. All rights reserved. Printed in the United States of America.
Isolation Transformer System with Single-Phase 120-Volt Input with Grounded Secondary. Shield Grounded
on Shore. Metal Case Grounded on the Boat.
The green grounding wire from the shore inlet is connected to
the isolation transformer shield. The green grounding wire is connected to the shell of the power inlet which is
insulated from the hull of the boat.
The ungrounded and grounded shore current-carrying conductors are connected from the power inlet to the
primary winding of the isolation transformer through an overcurrent protection device which simultaneously
opens both current-carrying shore conductors. Fuses shall not be used in lieu of the simultaneous trip devices.
120-Volt branch circuit breakers are permitted to use single-pole breakers in the ungrounded current-carrying
conductors.
The secondary of the isolation transformer is grounded (polarized) on the boat.
The boat grounding system (green) conductor is connected from the metal case of the isolation transformer to
all noncurrent-carrying parts of the boat’s AC electrical system including the engine negative terminal or its
bus without interposing switches or overcurrent protection devices.
ÉÉ
ÉÉ
ÉÉ
ÉÉ
ÉÉ
ÉÉ
ÉÉ
Ungrounded Conductor (Black)
Grounded Neutral Conductor (White)
Grounding Conductor (Green)
Shore Connection
Shore Power Cable
Shore Power Cable Connector
2-Pole, 3-Wire Grounding
Type Plugs & Receptacles
Shore Side
Boat Side
Power Inlet
(Electrically insulated
from the Boat)
Main Shore Power
Disconnect
Circuit Breaker
Transformer Case
Encapsulated Single Phase
Isolation Transformer
To Engine Negative
Terminal or its Bus
Black
White
Green
120 VAC
Grounding
Type
Receptacle
120 VAC
Device
Branch
Circuit
Breaker
(Typical)
Transformer Shield
(Insulated from Case and Core)
Transformer Case
Ground Connection
Figure 2. Electrical Diagram
−
Method 1 (see Figure 4 for Wiring Connections)
