Split Phase 120/208 VAC Shore Power

We recently ran across an issue one of our customers was having with his 120/240VAC system. He had traveled to different marinas along the Florida coast and kept running into low voltage on his AC system. The issue was that some marinas were only providing 208VAC at their pedestals. This is a problem that only occurs in a boat plugging into 240VAC shore power and have an isolation transformer that takes the 240VAC and splits it into two 120VAC legs. He encountered this at 3 of the 10 marinas that he visited. We were able to remedy the problem by rewiring his existing isolation transformer and adding a breaker panel to control it. The customer wrote an article for the Mainship owners forum explaining what was involved and how the system works.

Below is a link to the article.

208VAC MS400 Report


Chafe Protection and Wire Support

20160310_10063620160310_101144314-P1200746genshrimpThese photos are a prime example showing why chafe protection is a safety concern on boats. This incident happened when these conductors were running through a bulkhead with no chafe protection. Boats are constantly flexing and moving. Over time the rubbing against the wood bulkhead broke through the insulation on these wires. The picture with the chafed red wire is the positive wire running from the windlass solenoid to the windlass. The picture with the white wire shows a two conductor wire running to the solenoids: one positive and one negative. The negative cable shorted out with the positive running to the windlass. Luckily the red cable was only hot when the windlass was being used, as it was on the downstream side of the solenoid.

Heat and wood bulkheads can lead to a catastrophic fire on a boat. Some kind of chafe protection should be used whenever routing wiring around anything that may cause physical damage to the insulation. This can be accomplished with; split loom, grommets, silicone, electrical tape, conduit, ect. These are all inexpensive ways to avoid much larger problems in the future. Supporting conductors is equally important. ABYC standards state that wiring must be supported throughout their entire length or at least every 18”.

Electronics Integration

As technology progresses, the systems on our boats become more and more integrated. This is true for all different types of systems. One of our most recent installations is a prime example of this. We installed a Fusion RA70N and a new Garmin GPSMap 7612xs. Fusion has designed this stereo to connect to the Garmin gps through a NMEA 2000 port on the back of the stereo. We ran a drop cable to the NMEA 2000 backbone and the integration was seamless. This allows full operation of the stereo on the screen of the gps. The customer can now control the stereo from the helm even though the stereo is mounted elsewhere. The stereo also has Bluetooth and can be controlled 065-P1240531with a cellphone, tablet, or other compatible Bluetooth device. We are very pleased with the seamless installation and integration of these products and would recommend them to anyone looking for convenience and integration in their marine electronics.

See the Fusion RA70N

See the Garmin GPSMap 7612xs

Wire Sizing

Voltage Drop TableWhen designing/installing any electrical circuit, there are many things to take into account. The size of the conductor needed in the system is critical. Undersized conductors create increased resistance resulting in heat and voltage drop. When sizing cables, we refer to the ABYC tables for voltage drop. ABYC provides two tables: One table provides cable size for a system in which a 10% voltage drop is acceptable; the second when a 3% voltage drop is acceptable. On a boat, it is prudent to use the 3% voltage drop table due to the extreme conditions of a marine environment. ABYC E-11 Table IX shows the accepted wire size for a 3% voltage drop. When sizing wires with this chart, it is important to remember that the length of the conductor in the chart refers to the entire length of the circuit: both positive and negative. The chart also needs the total number of amps being used in the circuit. If for instance you have five 12 volt lights in a circuit at 1 amp each, you would use 5 amps as your total current, in amps, on the chart. This is just one of the many considerations that need to be made when designing a sound electrical system. Stay connected!


New Website! Same great technicians! We have many exciting plans for the future. This is where you can come to see what we are up to here at Apollo Marine Solutions. We come across many interesting things in our line of work and would like to share them with you here. Thank you for choosing us for all of your marine electrical needs.

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