Electrical Diagrams
Select desired installation configuration diagram by clicking on this table.
| Shore Power | Boat’s Electrical Panel | Electrical Schematics | |
|---|---|---|---|
| Single MP | Dual MP | ||
| 120V 30A (3 wires) |
120V | 120V/120V | NA |
| 120V/240V | 120V/240V | NA | |
| 240V 50A (4 wires) |
120V | S240V/120V | NA |
| 120V/240V | S240V/240V | D240V/240V | |
Overload Protection
Isolation transformers must be protected from overload by a dual pole disconnect circuit breaker between the shore cable entry point and the transformer’s primary side. The breaker rating must be equal to or less than the transformer continuous current rating, 30Amp for a 120V MP3.6, 25Amp for a 240V MP6, 50Amp for an MP6 configured for 120 V input and 50A for a set of Dual MP6 with 240V input. D-curve (delayed action) circuit breakers are recommended.
Inrush Surge
Marine-Pucks feature toroidal (ring-shaped) isolation transformers, which are lighter and more compact than traditional transformers. When turned on, they may experience a brief Inrush Current surge, which may, in a rare event, cause the input circuit breaker to trip. An efficient remedy is selecting D-curve (delayed action) circuit breakers – Another solution is incorporating an NTC resistor(thermistor) in series with the transformer’s primary winding. Since mid-2024, a thermistor has been standard, included in the larger model MP6 transformers. It can also be mail-ordered for retrofitting in older installations.
Case Double Insulated from Boat Ground
Marine-Puck transformers are encapsulated inside a cup-shaped plastic enclosure, providing double insulation like most electric hand tools today. The ABS resin case combined with solid epoxy potting compound eliminates shock and fire hazards due to broken or loose conductors touching a metallic case and effectively prevents seawater ingress.
Certifications
UL Marine is certified to UL 1561 Power Transformer Standard.
IMANNA Laboratories, Certified Ignition Protected
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