Marine Refrigeration and Marine Wood Repairs
Over the last two months, I spent the majority of my free time installing a large solar off grid battery pack on my boat. This battery pack will primarily be responsible for powering an electric outboard motor, but it will also be used to run my marine refrigerator. I also spent a couple days installing some marine grade ply to fix a few drafts around the bed.
Building a Solar Powered Fridge
Marine refrigeration is an incredibly handy thing to have on a boat, but it can also be a very difficult and expensive to install. My boat came with a 12v refrigerator that also runs on 120v. The 12v side was never connected and we run it exclusively on 120v. With the electrical system I’ve installed, we don’t need to connect it to our 12 volt system, but it’s nice to know that we have the option.Regardless of the voltage that a marine fridge operates at, the power will be the same. For example, using my Kill-o-Watt meter, I was able to determine that my small refrigerator freezer takes about 1.25 amps at 120 volts AC. That’s approximately 150 watts of power (1.25 x 120 = 150). To operate at 12 volts, the marine fridge would require approximately 12.5 amps (150 / 12 = 12.5). Either way, it takes the same amount of power.
Maintaining this heavy current draw is why boat refrigeration is so difficult. Of course, this small refrigerator freezer won’t be running constantly as the compressor only turns on to maintain the temperature inside the marine refrigerator as needed.
In order to cut down on the electrical energy required while on the hook, we load our solar powered fridge with ice to provide ‘free’ thermal energy. We leave bottles of water in the freezer when the boat is at the dock and connected to shore power. We then move these frozen bottles into the 12v refrigerator while underway. When we get back from the trip, we put the bottles back into the freezer. That way there is no mess with melted ice, and in an emergency we can drink the water.
Stopping Cold Drafts with Marine Grade Ply
Boat refrigeration isn’t the only ‘cool’ thing on my boat. Ever since we bought the Rock ‘n Row there has been a gap in the wall that separates the bilge from the bedroom. Like a drafty house, cold air creates an air flow due to the temperature differences. It makes the far side of the bed (my side) uncomfortably cold. To make matters worse, the bed is built right over the marine toilet system, so any draft will bring in the slightest scent of sewer when I pump out the head.
Cold drafts are a common problem for Pacific Northwest boats. Year round boating in this area requires heat. Heat differences creates air flow, which gives Pacific Northwest boating a lot in common with a drafty house. In order to stop the draft, I installed marine grade ply into the wall to seal up the draft. If this isn’t as effective as I’m hoping, I’ll come back later and use calking to seal up the edges in order really minimize any leftover cold drafts.
The cost of marine plywood is higher than other types of plywood, but after some significant research, I decided to shell out the extra money. The use of different types of plywood is hotly debated on boating forums. I could have used exterior grade plywood or pressure treated plywood instead. However, exterior plywood has gaps and voids throughout the layers. These gaps provide an excellent living space for the mold that creates dry rot and health hazards. Pressure treated plywood is infused with chemicals that fight off this mold, but it also releases toxic gasses over time. Since I *know* that there is a cold draft wafting up from the bilge, this means any toxic fumes or mold spores will be blown right into my face as I sleep. For these reasons, I decided to go with marine grade ply as the best material to use for this application.