Is Your Boat Wired to Melt?

On a client's boat recently, we saw that the wiring was chaotic to say theĀ  least. But take a closer look at the two 3 conductor 14 AWG AC wires which go up to the main DC distribution panel. They are labelled "Batt. 1" and "Batt. 2." At some point, this boat must have had two house battery banks, but they have since been combined into one house bank.

There are several things wrong with this wiring. First of all, we do not use AC wires for DC connections as mentioned in this previous blog. The colours are all wrong and can lead to confusion later on. To add to the confusion, on the "Batt. 1" wire, green and white go to the positive bus and black goes to the negative bus, but on the "Batt. 2" wire, green and black go to the negative bus and white to the positive bus. One green is positive and the other is negative. This second photo is a close-up of one of the green wires. The insulation is all melted, exposing the conductor in places along the whole length of the wire.

Two things could have happened here. Sometimes people double or (in this case) triple up smaller gauge wires to increase ampacity. Using several smaller gauge wires instead of upgrading to a single larger wire is hazardous. If one or two wires get disconnected, then the remaining wires may not be able to handle the current. This could have caused this wire to overheat and melt unnoticed. But the most likely scenario is that the previous installer got confused about which green was which, and shorted positive to ground. That would mean that when the installer realized the mistake, which would be immediately obvious, he or she didn't bother to replace the damaged wire. This is a very dangerous situation because the melted green wire is in the same sheath, touching the white and black wire. This could have killed anyone who touched the wiring. Standards exist for a very important reason. A comparison would be that you can drive on the other side of the road, but everyone's going to drive on the right side and expect you to drive on the right side as well. It may work to drive on the left side, but likely would not end well.

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