Lots of folks are confused about shore power, how it should be supplied, how to connect to it, and how to make certain the wiring in your boat is kept safe so I thought I would try to put together a BASIC outline for 120 volt 30 amp service.
Let’s start with the supply which is usually on the shoulders of the marina / slip owner. The NEC (National Electrical Code) has been updated in the last few years and tougher requirements have been put in place. If your marina operator is not up to code it’s time to have a serious talk to him / her and politely but forcefully insist everything be brought up to code.
1. A receptacle (outlet) MUST provide 30 Amps of service as a minimum.
2. The receptacle MUST be of “locking” and “sealed” design. (It MUST be weather proof with or without a cord plugged in.)
3. The receptacle / circuit MUST be protected by a GFCI (Ground Fault Circuit Interrupter) with a maximum trip amperage of not more than 100ma.
4. The receptacle and raceway (Conduit) MUST provide a grounding conductor. (The conduit may NOT be used as a ground. It is however REQUIRED to be bonded to the grounding conductor.)
5. The receptacle box MUST be supported by structural members of the slip / dock. (It can NOT be supported by just the conduit.)
6. Each Receptacle MUST have a disconnect switch or circuit break / switch that can be turned off.
7. Each receptacle MUST be on its own protected branch circuit.
Ok, now let’s look at what you are required to use to connect to shore power.
1. Both end of the connecting cord MUST be weather tight.
2. Both ends MUST be of the “locking” design.
3. Only cord with the designation of SO, ST, or STO may be used.
4. Cords MUST be of at least 10 gauge, stranded wire with three conductors.
Distribution and wiring in the boat.
1. A weather tight distribution / breaker panel MUST be used. (Unless mounted in a protected cabin.)
2. There must be a main circuit breaker and it may not exceed the amp rating of the service. (30 Amps)
3. The distribution panel MUST provide separate busses for neutral and ground connections. (Unlike home wiring / distribution panels, the neutral may NOT be connected to a common bus with the ground under any conditions.)
4. All wiring in the boat MUST use three conductors. (Hot, neutral, and ground. Conduit shall NOT be used to ground a circuit but it must be grounded if present.)
5. All wiring must be stranded. (Solid conductors like home use Romax are NOT allowable.)
6. All receptacles MUST be of three prong design, MUST be designed to eliminate polarity reversal, and MUST provide a ground.
7. Each circuit MUST provide a GFCI. (Multiple receptacles may be protected by one GFCI.)
8. The shore power ground MUST be bonded to the 12 volt grounding system of the boat.
9. The drive MUST be bonded to the 12 volt electrical system. ANY metal components in or below the water line MUST be bonded to the 12 volt electrical system.
10. All wiring connections MUST be made at a terminator. (No wire nuts or twisting wires and taping them.)
I’ll say it again, this is a BASIC outline and there are many situations and conditions that would require additional safety and or wiring changes. (The use of invertors, gensets, battery chargers, etc.) If you are uncertain, do yourself, your friends and the other boaters at the dock a favor and hire a professional.
Let’s start with the supply which is usually on the shoulders of the marina / slip owner. The NEC (National Electrical Code) has been updated in the last few years and tougher requirements have been put in place. If your marina operator is not up to code it’s time to have a serious talk to him / her and politely but forcefully insist everything be brought up to code.
1. A receptacle (outlet) MUST provide 30 Amps of service as a minimum.
2. The receptacle MUST be of “locking” and “sealed” design. (It MUST be weather proof with or without a cord plugged in.)
3. The receptacle / circuit MUST be protected by a GFCI (Ground Fault Circuit Interrupter) with a maximum trip amperage of not more than 100ma.
4. The receptacle and raceway (Conduit) MUST provide a grounding conductor. (The conduit may NOT be used as a ground. It is however REQUIRED to be bonded to the grounding conductor.)
5. The receptacle box MUST be supported by structural members of the slip / dock. (It can NOT be supported by just the conduit.)
6. Each Receptacle MUST have a disconnect switch or circuit break / switch that can be turned off.
7. Each receptacle MUST be on its own protected branch circuit.
Ok, now let’s look at what you are required to use to connect to shore power.
1. Both end of the connecting cord MUST be weather tight.
2. Both ends MUST be of the “locking” design.
3. Only cord with the designation of SO, ST, or STO may be used.
4. Cords MUST be of at least 10 gauge, stranded wire with three conductors.
Distribution and wiring in the boat.
1. A weather tight distribution / breaker panel MUST be used. (Unless mounted in a protected cabin.)
2. There must be a main circuit breaker and it may not exceed the amp rating of the service. (30 Amps)
3. The distribution panel MUST provide separate busses for neutral and ground connections. (Unlike home wiring / distribution panels, the neutral may NOT be connected to a common bus with the ground under any conditions.)
4. All wiring in the boat MUST use three conductors. (Hot, neutral, and ground. Conduit shall NOT be used to ground a circuit but it must be grounded if present.)
5. All wiring must be stranded. (Solid conductors like home use Romax are NOT allowable.)
6. All receptacles MUST be of three prong design, MUST be designed to eliminate polarity reversal, and MUST provide a ground.
7. Each circuit MUST provide a GFCI. (Multiple receptacles may be protected by one GFCI.)
8. The shore power ground MUST be bonded to the 12 volt grounding system of the boat.
9. The drive MUST be bonded to the 12 volt electrical system. ANY metal components in or below the water line MUST be bonded to the 12 volt electrical system.
10. All wiring connections MUST be made at a terminator. (No wire nuts or twisting wires and taping them.)
I’ll say it again, this is a BASIC outline and there are many situations and conditions that would require additional safety and or wiring changes. (The use of invertors, gensets, battery chargers, etc.) If you are uncertain, do yourself, your friends and the other boaters at the dock a favor and hire a professional.
