ABYC E-11 is the standard that governs AC and DC electrical systems on boats, including shore-power isolation transformers. The current edition is ABYC E-11-2025, AC and DC Electrical Systems on Boats. It revises E-11-2023. The August 2025 transformer updates take effect in August 2026.
MarinePuck is built for that standard. It is not an ABYC certificate. ABYC writes the rule. UL lists the hardware. The yard makes the install. A Dual MP6 or a pair of Dual MP6 systems meets ABYC E-11 on a 30A, 50A or 100A boat when the ELCI is on the input and the secondary is bonded the way the diagram shows.
What ABYC E-11 actually covers
E-11 is the electrical standard for boats. Shore power, grounding, overcurrent, ELCI, and transformers all sit in it. There is no separate “ABYC isolation transformer” standard. If a yard asks what MarinePuck meets, the answer is ABYC E-11.
Two configurations live in that standard.
| System | What it does | Green wire |
|---|---|---|
| Polarization transformer | Fixes polarity. Shore ground stays continuous | Unbroken. Needs a galvanic isolator if you want DC blocking |
| Isolation transformer | Breaks shore from boat | Shore green stops at the primary. Boat green starts on the secondary |
MarinePuck is the second one. A galvanic isolator is not a substitute. An isolator only blocks low-voltage DC on the green wire. ABYC E-11 still treats that as a polarization path, not isolation.
What changed in 2025
Before 2025, E-11 isolation practice assumed a laminated, encapsulated dry-type transformer, a metal shield between primary and secondary, and a metal case with a grounding terminal. A toroidal puck in a non-metallic shell did not match that picture, even when the electrical job was the same.
The 2025 revision opens that.
| Rule | Before 2025 | ABYC E-11-2025 |
|---|---|---|
| Core | Laminated, encapsulated | Encapsulated dry-type, toroidal included |
| Listing | UL 1561 expected | UL 1561 required |
| Metal case | Required, with a ground terminal | Not required. A ground terminal is required only if the case is metal |
| Metal shield | Required between windings | Not required if an ELCI is installed on the input |
| Effective | Through the 2023 edition | August 2026 |
That is the sentence for a 50A or 100A quote. MarinePuck is an encapsulated dry-type toroidal transformer, UL 1561 Recognized, UL Listed Marine file E509703, in a non-metallic ABS shell. The shield exception is the ELCI on the input. Without that breaker, the 2025 path is not met.
The ELCI is the compliance piece
Older E-11 language still confuses yards. An ELCI is not required where an isolation transformer is installed within 10 feet (3 m) of the shore inlet. That exception is about the transformer already isolating the boat. It does not remove the overcurrent disconnect. ABYC has said the shore disconnect still belongs within 10 feet of the inlet. If the transformer is farther than 10 feet, both overcurrent and ground-fault protection are required.
The 2025 shield rule is stricter than that exception, and it is the one that matters for MarinePuck.
| Device | Job | On a MarinePuck install |
|---|---|---|
| Shore disconnect / overcurrent | Opens a short. Required within 10 ft of the inlet | Always |
| ELCI, 30 mA | Opens on leakage. Also the 2025 substitute for a metal shield | On the input, ahead of the puck |
| Galvanic isolator | Blocks DC on an unbroken green | Do not add one on the shore green. The green is capped |
Put the ELCI in front of the transformer, as close to the inlet as the run allows. That is the install step that makes a non-metallic MarinePuck an ABYC E-11 isolation transformer. Soft start on MP6 and Dual MP6 is what keeps that 30 mA device from opening on inrush. It is not the compliance device. The ELCI is.
50A and 100A, sized to the inlet
ABYC E-11 does not invent a special amp rating. The transformer has to carry the shore inlet.
| Inlet | VA | MarinePuck | ELCI / disconnect |
|---|---|---|---|
| 30A, 120V | 3.6 kVA | MP3.6 | 30A, ELCI on the input |
| 50A, 120V | 6 kVA | MP6 | 50A class, ELCI on the input |
| 50A, 120/240V | 12 kVA | One Dual MP6 | 50A double-pole, ELCI on the input |
| 100A, 120/240V, or two 50A cords | 24 kVA | Two Dual MP6 systems | 100A class, or one ELCI per 50A inlet |
A 50A, 240V boat is one Dual MP6. A 100A boat is two Dual MP6 systems. One puck does not satisfy a 100A inlet, and an undersized transformer is not an ABYC E-11 install no matter how correct the bond is.
How the landing meets E-11
Class II is the difference from a steel Charles or Hubbell box. There is no metal case to bond. The shore green is capped and insulated. It does not land on the puck.
| Conductor | Where it goes |
|---|---|
| Shore ungrounded (hot) | Primary, through the ELCI and the disconnect |
| Shore neutral | Primary. Not bonded to boat neutral |
| Shore green | Capped. Not brought to boat ground |
| Secondary hots | Boat panel, after secondary overcurrent |
| Secondary neutral | Bonded to boat AC ground at the transformer secondary, one place only |
| Boat green | From that same bond to the panel ground bus |
One neutral-to-ground bond. Transformer secondary or panel, not both. A second bond puts neutral current on the green and undoes the isolation ABYC E-11 is written to create.
Generator and inverter outputs get their own bond at their own source, through the transfer switch, not by tying those neutrals to the shore secondary. Twin inlets stay separate. Do not common the neutrals of two 50A cords on the boat.
Ignition protection is the other E-11 clause that lands on this hardware. In a gasoline machinery space, an ignition source has to be ignition protected unless it is isolated from the fuel system. MarinePuck is ignition protected (IMANNA 21-21794-1). That is the gasoline-boat box, not a substitute for the ELCI.
What the yard still has to do
The puck does not make the boat compliant by itself.
- ELCI on the input, ahead of the primary
- Overcurrent disconnect within 10 feet of the inlet
- Secondary neutral bonded once, per the MarinePuck diagram
- Shore green capped
- Conductors sized for 50A (6 AWG class) or 100A (2 AWG class)
- Secondary breaker sized for the inverter, the panel, and the puck, not for the dock
- No galvanic isolator in series with a capped green
- Ignition-protected device left ignition protected. Do not open the shell
Boost taps (104V and 208V on Dual MP6) are a voltage choice for a 208V dock. They are not an ABYC E-11 requirement. Land them when the marina sags. Leave them off on a solid 240V yard.
50A versus 100A on one drawing
| 50A | 100A | |
|---|---|---|
| Hardware | One Dual MP6, two pucks | Two Dual MP6 systems, four pucks |
| kVA | 12 | 24 |
| ELCI | One, on that inlet | One on a 100A inlet, or one per 50A cord |
| Bond | One secondary bond | One bond per isolation system |
| Green | Capped at that inlet | Capped at each inlet |
| Miss that fails E-11 | ELCI omitted, or neutral bonded twice | One Dual MP6 on a 100A inlet |
What this is not
ABYC E-11 is a design and installation standard. MarinePuck is UL Listed Marine and built to be installed to it. It is not an ABYC-listed label, and a steel box is not required after the 2025 revision. The install is what a surveyor checks: ELCI ahead of the puck, one secondary bond, green capped, inlet matched to kVA.
FAQ
What ABYC standard does MarinePuck meet?
ABYC E-11, when the ELCI is on the input and the secondary is bonded per the diagram.
Is MarinePuck ABYC certified?
No. ABYC does not certify transformers. The hardware is UL Listed Marine, E509703, UL 1561. The install is what meets E-11.
Why the ELCI if the transformer is within 10 feet?
Older E-11 can waive the ELCI inside 10 feet. The 2025 shield exception does not. No metal shield means the ELCI has to be on the input.
Does a 100A boat use one Dual MP6?
No. 100A is 24 kVA. Two Dual MP6 systems.
Where does the shore green go?
Capped. MarinePuck has no metal case to bond it to.
Where is it made?
Shelton, Connecticut.
Product callout
Bridgeport Magnetics MarinePuck
ABYC E-11 isolation on a 50A inlet is one Dual MP6 (12 kVA). On a 100A inlet it is two Dual MP6 systems (24 kVA). ELCI on the input. Secondary neutral bonded once. UL Listed Marine E509703, ignition protected, made in the USA.
Phone: (203) 954-0050
Email: [email protected]
bridgeportmagnetics.com/marine-isolation/
