LT
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ISOG26
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1
Issue 1 Print 2
7
Charles Industries, Ltd. All rights reserved. Printed in the United States of America.
Note:
This diagram does not illustrate a complete system. Refer to the appropriate ABYC text.
Isolation Transformer System with Single-Phase 120-Volt Input with Ground Fault Protection and Grounded
Secondary. Shield and Metal Case Grounded on the Boat.
The green grounding wire from the shore inlet is not
connected to the isolation transformer shield or metal case. 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 a ground fault 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 shield and 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.
ÉÉÉ
ÉÉÉ
ÉÉÉ
ÉÉÉ
ÉÉÉ
ÉÉÉ
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
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
Transformer Case
Ground Connection
with OFP
with Metal Case
Figure 3. Electrical Diagram
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Method 2 (see Figure 5 for Wiring Connections)
