By: Captain James Clausen

For the first 20 years of my boating life I have never even considered climate control as a part of boating. Boating was basic, with the elements “in your face”! I was also younger, poorer, and had much smaller boats, and technology had not caught up with boating. I herein confess to having two AC units aboard our present boat, neither of which was installed correctly by the factory, which I’ll explain in below. But, before that happens, just look around your local marinas this summer, the water you see exiting from the hulls of most of these larger boats is not their bilge pumps hard at work, but it’s the AC’s heat exchangers, pulling the cool out of the seawater and exchanging the AC’s heat into it. This is a boating fact that I explain to dock walkers visiting our marina about once a month, and I confess it’s one that I didn’t know or understand when I owned smaller boats. Boating knowledge varies with the type of boating we do, just because we’re all out on the water, we all don’t understand all of the aspects of boating, I hope to learn something new every day. And that just what happened when I got into understanding boat air conditioning. Lets start with the simplest and least expensive AC for our boat. To my mind that is a portable AC unit that fits onto a overhead hatch, that is brought out when you get to a dock, and plugs into a extension cord. Quite popular and inexpensive on small cruisers, easy to install and easy to move from boat to boat. Next lets talk about window AC units, also a inexpensive alternative on houseboats and older cruisers, where comfort and economy come before traditional maritime good looks. Having considered these installations and dis-guarded them for a more perminet solution, what’s out there? Well, the most installed system is a self contained, central unit that both heats and cools, and uses the water around the boat to exchange the units unwanted thermal load. Most of today’s units have electronic temperature controls that allow you to set your boats temperature just like your house. They are small, just 60 pounds for a 7,000 BTU unit, and take reasonable power to run, in this case just around 4 amps @ 110 volts. For a small boat owner with average tool skills, this is a do it your self project, each unit comes leak checked, and pre-charged. You will need to first figure out the volume of your space you want to climate control, this will determine the BTU size of the equipment you need to install. Once you have the size of the unit, you can go shopping for a manufacturer, for this example we will chose Marine Air, and their 7,000 BTU cabin mate unit, the unit itself is going to require just over a one foot, by a foot and a half of footprint. Ideally the unit is placed above the water line, so that the condensate drain can have a gravity flow back into the surrounding water. Many installers simply install the unit in a closed space and eliminate the supply air flexible ducting, easier yes but read on. While leveling of the unit is preferred for ideal compressor life, tilting of the unit to allow the condensate water to drain from the catch pan should be considered. With the unit location, and inlet air grill location picked out, we must locate the cool air grill, the boat itself usually dictates where things like this can and cannot fit. Ideally it should be in the top half of the room or at least facing the ceiling. Depending on your requirements you may need two ducts, one for a forward cabin and a second for the main cabin. Next locate your seawater pump, it must be installed below the waterline, as they not self priming, and at the beginning of each season or for the trailered boat, each launching, you will need to manually “prime the pump.” The digital controller location should be selected out of the direct path of the exhaust air and direct sunlight, as the rooms air temperature sensor is located in the control panel. If this is not possible, there is a remote sensor available from marine air, it is inexpensive and we have mounted ours in the return path, of the return air grill with great success. Holes in the boat, we need to add three holes in the boat, two if you can “T” into another drain for the condensate. One for the seawater pump intake, a second for the overboard discharge, and the last, if needed for the condensate. Power wiring is done to your AC power panel. Alternatives to the system described above include a chilled water system and a installation of a residential or RV roof mount AC unit.

Simple, yes it can be, and you can take your time with the installation. The instructions the manufacturer gives to the purchaser are very complete, and the equipment is robust, and made to live in a marine environment. Whether your doing a new install or already have units installed, here is some additional information to make your installation much better.
You can decrease the noise from the units compressor by baffling the intake air or using an intake duct. If you have more than one space that you will be supplying air to, be sure to add a path for the return air. In the photo below the maker of this quarter of a million dollar boat tried forcing air into a room with no why for it to get back to the unit. The result was good daytime AC and heat, but at night with the doors closed the air was pulled through the bilge and sidewalls making the boat smell and the temperature unstable.

The installation of these simple vents brought the system into balance and stabilized the temperature swings.

Clean your intake and clean your fins, we do this with a horse hair bristle brush on the vacuum, and when it gets clogged further inside we use compressed air. If the problem get worse than this the unit must be taken out and have an acid cleaning. Its worse than it sounds, and will purge all the nastie's out of the unit and allow for the renewed air flow through the coils. Yes, you can do this yourself or if you take your unit to an AC shop they will do it there for you, sometimes while you wait..

This unit is in the process of being cleaned, the acid reacts with the dirt and the metal of the fins and actually pushes the dirt out that was trapped inside of the coil space, as it does, it creates heat and some acid fumes. Read the directions, follow the directions.

Use real air filters, toss the metal reusable metal mesh type away. The way to prevent your AC fins from clogging is to filter the air before it enters the fins! We use this reusable plastic type screen filter, we wash it clean monthly in the kitchen sink as a maintenance item.

Clean your air ducts and condensate pan. Mold and smell develop here and will be pushed along with your nice clean air throughout the boat. How would you like to turn on your AC and have it smell of mold or worse. We found this product at home depot and it has worked very well for us. Commercial installations use tablets in the condensate pan, unavailable to the normal boater, additional advise, a little goes a long way.

For more information from the Maxum Sports Yacht Owners Group,
send your name, hull #, and tip, if you have one to James, @BilleGates@aol.com