This article originally appeared in Practical Sailor Magazine.
Years ago, one of the many projects during the refit my aging 36’ Luhrs sedan cruiser was to replace the AC wiring system with one that meets modern ABYC Standards. The first step in this project was to replace the broken and charred shorepower inlet. During this process I came across a requirement that is often overlooked in late model boats, and non-existent on older boats like mine. ABYC Standards state that the main AC shore power disconnect breaker must be located within 10’ of the shore power inlet. This is an important requirement intended to limit the amount of cabling within the boat that could potentially short circuit and cause a fire. On my boat the distance to the distribution panel is over 20’ when measured along the cable. Although the standards permit the breaker to be installed anywhere within the first 10’ it is best to locate it close to the shore power inlet thus protecting as much wire as possible inside the boat. Blue Sea Systems, Inc. (www.bluesea.com) sells a small 30 amp AC double pole breaker with a reverse polarity indicator that works well in this situation.
The first obstacle was to find a suitable location for the breaker that was close to the shorepower inlet. The breaker is not ignition protected so it is important that it not be installed in a space connected to the engine or fuel tank compartment. Fortunately there is a void space where the shorepower inlet enters my boat adjacent to the aft cabin bulkhead. As a result I was able to mount the breaker on the aft bulkhead less than eight inches from the inlet. ABYC Standards state that connections normally carrying current should be made in enclosures to protect against a shock hazard. However the void area where my panel is installed is inaccessible therefore I felt the potential for electrical shock was minimal and did not install the breaker in a dedicated enclosure. This is not the best solution and proper enclosures should be used whenever possible.
Mounting the panel is easy with the supplied template and a jig saw. Throughout the re-wiring of my boat I’ve used only quality marine grade cable. This cable is manufactured from many fine strands of copper that protect the cable from breaking due to the constant vibration and shock impacts found on a boat. The copper strands are individually tinned to increase their corrosion protection. The use of solid core copper wire (e.g. Romex residential cable) is not permitted under ABYC Standards, and should never be used onboard a boat. Being an older vessel, my boats’ entire AC system used solid core copper wire which was my main reason for bringing the system up to modern standards. A minimum of 10 AWG cable should be used for a 30 amp shore power connection. The wire connections were made using marine grade crimp fittings and a purpose made crimping tool. The tool I use is manufactured by Ancor (www.ancorproducts.com) and cost about $60.00; it is designed to crimp wire up to 10 AWG. The crimping tool has a ratcheting mechanism that forces you to apply the right amount of pressure to create a secure connection. The tool crimps the fitting in two places (at the barrel and support sleeve) in one squeeze of the handle. I used ring crimp fittings at all connections. Ring fittings or captive spade fittings provide a secure connection and should be used whenever possible and should always be used on cables carrying over 20 amps.
Wiring the shorepower inlet to the breaker panel is straight forward. First make sure that all sources of onboard AC power are disconnected. That includes shorepower cables, inverter/chargers, and gensets. Three wires must be connected between the shorepower inlet and breaker panel, the hot wire – normally black, the neutral wire – normally white, and the grounding wire – normally green. The breakers are labeled to show where the hot and neutral wires are connected. It further shows where the “LINE” and “LOAD” cables should be connected. LINE refers to the wires coming from the shorepower inlet to the breaker; LOAD is the wires from the breaker leading to the AC distribution panel on the boat. Only the black and white wires are connected directly to the circuit breakers. A screw located at the top of the breaker panel has a small green wire attached to it. The green grounding wires from both the shorepower inlet and AC distribution panel are connected there. Be sure to support all cable runs between fixtures with supports every 18”.
Working with your boats’ shorepower system can be dangerous and potentially fatal. If you are unsure of your skills hire a qualified marine electrician, preferably one who is ABYC Certified.