Originally Posted by St. Elsewhere
What is the correct configuration for grounding and the neutral with an isolation transformer installed?
When an isolation transformer is properly fitted is the shore power neutral grounded through the shore power cord on the primary side only?
I found the answer to my question in a Charles Industries isolation transformer installation
"Isolation Transformer System with Single-Phase 240-Volt Input, 120/240-Volt Single-Phase Output with Boat
Grounded Secondary. Shield Grounded on Shore and Metal Case Grounded on Boat. The ungrounded 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
Do not connect the shore neutral. Fuses
shall not be used in lieu of simultaneous trip devices.
240-Volt branch circuit breakers and switches simultaneously open all current-carrying conductors.
120-Volt branch circuit breakers are permitted to use single-pole breakers in the ungrounded current-carrying
Polarization of conductors must be observed in all circuits.
The green grounding wire from the shore is connected to the shore power inlet shell which is insulated from
metal-hulled boats. Do not connect the shore green wire to the boat ground.
The grounded neutral from the secondary of the isolation transformer and the case of the transformer are
connected to the system ground, neutral conductor and engine negative terminal or its bus."
There is also an option for using a ground fault interupter in place of a circuit breaker on the primay side of the transformer.
This may seem like "thread drift", but I believe that it means that if an isolation transformer is installed, an external portable generator could be connected to the shore power cord. The generator would appear electrically identical to standard shorepower from the boat since neither the neutral or the ground wire is connected between the boat and the generator. The circuit discussed here is a 120/240 volt configuration.
I do not know if there are code restrictions regarding the use of ungrounded portable generators on docks or if such generators have protection for leakage currents to their exposed conductive parts