The front of your electrical panel probably looks nice and orderly. These panels tend to consist of neat rows of switches with clear, black and white labels. And a pretty light beside each switch. However, depending on the age of your boat and the orderliness of the electricians over the years, it is very likely that the back of your electrical panel looks like something that would give Indiana Jones heart palpitations.
Whether your panel is a set of three DC switches or several rows and columns of switches divided into DC (usually on the left) and AC (usually on the right), it will be worth your time to get to know what is going on both on the panel and behind the panel. I once found myself helping a recent widow who knew little about the nuts and bolts of her boat. It was delivered by a friend, but when we went to check it out, the batteries were dead. Boiled completely dry, no room for recovery. Turns out, the labels on the electrical panel did not do what they said they did. A switch on the panel had been randomly assigned to the inverter, which ran all of the outlets, even when the boat was hooked up to shore power. A separate, unlabeled switch in the engine room was used to turn on the battery charger when hooked up to shore power. The boat had been left for a month or more drawing energy from the batteries to power the time on the microwave. I don’t know if I mentioned it yesterday, but while inverters may be awesome, they use a lot of DC power to mediocre amounts of AC power. It took us a full day of following wires to figure out what was going on in this case.
And that, unfortunately, is what it takes on most boats. My boat has an AC switch labeled “appliances.” What appliances? It isn’t like we have an electric stove, a 120v fridge or even a blender on board! We have followed the wires, but we still do not know what may have been on the far end of them, seemingly when the boat was built in the 1980s.
Start exploring by reading the labels. Flip a switch and see if the expected thing happens. Once you have flipped the switches and made your slip neighbors wonder why the lights are going on and off, get out a flashlight and turn of the main breakers for the DC and AC. Only then should you set about figuring out how to open your board. Once you have gotten behind your board, prepare to marvel. Perhaps you will get to marvel at the orderliness of it all, with harnesses and cable ties keeping everything in place. More likely, you will get to marvel at the sheer disorder, or perhaps at the fact that so many colors of wire have been manufactured. Hopefully, you will at least see some patterns. Red, blue, grey, white will likely be attached to the breakers themselves. Black wires may well be attached to a bar somewhere set off from the breakers. This is called a bus bar. Everything that is connected will need to have both the positive and negative wires attached to work, most of the negatives will be on this bar. You may also find negative bus bars located near clusters, such as where your batteries are located or the helm.
While you were following your wires, did you find any unattached wires in your lazarette? Your cabin? Follow these back to the board – hopefully your board is still turned off, in case some prior budding electrician decided to uninstall an instrument and leave the live wires just dangling in space. We have removed miles of wiring in this way from Sea Story.
If you keep following wires and back and forth, you will get to know your whole boat better than you ever thought possible. While it may not always be possible to follow the wires through a conduit, at least you will know where the conduits are so that you don’t accidently drill through your wiring in the future. However, if you have a household member around, you may be able to follow the wiring through the conduit if you can find the other side. One person stands at one end and wiggles the wire they are interested in until the other person identifies the other end.
This may all seem like rather a lot of busy work, and maneuvering through the crawl spaces of your boat involves more uncomfortable positions than sitting at home reading Nigel Calders’ Electrical Manual. But if you can make time to do it when you would otherwise be sitting home twiddling your thumbs, it is the kind of hands on learning that can prove invaluable when you have to replace your bilge pump or trouble shoot why your GPS won’t come on.
Just make sure you turn off the main switches! If we are actually going to be doing any wiring, I even take the time to unplug the boat from shore power.
Keep safe, keep learning