By Scott Herrick
Although we have loved sailing Double Dutch, our Catalina 30, for the past year, the weather in the panhandle of Florida is sometimes “breathtakingly warm” while the winter nights can be "very nippy." We have often looked longingly at the boats that have a constant stream of water pouring out of an overboard while all the hatches and windows are shut tight. The “carry-on” air conditioner we had brought with us when we moved up from our 27-foot sailboat just wasn’t hacking it, trying to cool the much larger interior on Double Dutch. Likewise, the ceramic heater did very little to make us want to abandon our sleeping bags during the winter.
There are several places where you can buy air conditioners for your boat, but your best bet is to do some shopping around. Don’t automatically go with the one that has the best looking add in the magazine. One of your best resources when looking for a good unit will be the internet. Most every manufacturer will have a site expounding the wonders of their particular machine. After reading enough of these, you will begin to feel that there is no way to make a really good decision. Have faith, there is.
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First, do the one thing that will serve you best: talk to others in your area who have air conditioning on their boats. The best situation is if you can find someone who has a boat exactly like yours. After that, close is good. Listen to them, not only in regard to the size of the unit or the cost of the original installation, but get them talking about maintenance. How often has the machine broken down? How much did it cost to get it repaired? Did you have to have a specialist come in to fix it, or were you able to do the repairs yourself. I happen to be one of those people that will try to fix anything (within reason) and quite often succeed. If you don’t happen to be one of those, check on where the closest people are who work on the unit you are considering.
The next biggest question is going to be “how big." Again, on the web sites, you will find graphs and calculations you can use to determine this. Remember that these are good starting points in figuring out what you will need. You need to factor in what the weather is like where you sail, or where you intend to sail. If you read in the chart that a boat with your expected inside volume requires a 10,000 BTU unit, don’t take that as gospel. Remember, if you are boating in Maine, that unit might be way too much, but if you are boating in Florida, it might be too small. Again, talk to the boaters around you. Use their input, along with the charts and calculations to start getting yourself into the right neighborhood.
Contrary to the popular belief among us men, bigger and more powerful isn’ t always a good thing. In the case of air conditioning, this is also true. If you buy a unit that is too big for your boat, it will end up cycling on and off in short bursts. This is not good for the compressor. It is referred to as “short cycling." By the same token, under sizing the unit is not good because it will be running almost continuously to maintain your desired temperature. Even if it does manage to keep up, it will be struggling to do so. Worse, it will run continuously and never catch up with your desires. This is why finding the optimal size is important. Just to throw another fly in the ointment, remember that March and July can both be air conditioning season. Shoot for a happy medium that will be big enough to keep up during July, but not run too short in March.
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Another consideration is the “add-ons” that the unit has. It is able to provide heat as well as air conditioning? Is this something you need? If it does, is it reverse cycle or resistance heating? This question may seem unnecessary, but it can be important. Just like a heat pump, there are limits to the temperatures that a reverse cycle can overcome. If you happen to have a great temperature variance where you live, you might want to look closely at the abilities of the heater. Another consideration is if you do live in a climate where the boat is going to be hauled during the colder months, do you want to have heat available for working on your boat while she sits on jack stands? If so, reverse cycle won’t work for you. Additionally, resistance heating only uses the system’s blower motor, so there is less wear and tear on the compressor and heat exchangers. With a reverse cycle unit, you will have to have a water supply hooked up if you are sitting on the hard for the heater to work. With resistance, all you need is shore power.
Your next consideration has to be size. We are talking about physical size here. This can be the trickiest part for a sailboater, since room isn’ t something that can be expended cavalierly. Remember, every cubic inch of space you give away for an air conditioner is one less cubic inch of something else you might have to leave behind. There are several areas that you might be tempted to try, but you have to look closely at the requirements of the unit you are considering. The unit I installed required that the unit be located inside the area that is being cooled. This meant that any idea of using that huge locker in the cockpit was out. You also do not want to locate the unit too close to the engine because of heat, or in a bilge pocket because of all the creepy nasty bacteria that can live down there. Luckily, there are usually spaces that don’t lend themselves well to stowage, if you just go looking for them. The two places I considered were a hanging locker and the area under the V-berth.
Now is when you start narrowing down the field. You should already know the size in BTUs that you need, but there are all shapes and sizes of air conditioners out there, and some that have different configurations of the same machine. Take the discharge for instance. Some units have a single discharge that goes to a distribution plenum (fancy word for a box with one “gozin” and several “gozouts”). Others will have a plenum built right into the discharge, so all the duct hoses have to come back to the unit. Some will have models that have top discharges and some will have side discharges, or you can order either configuration on the same model.
Your best friend on this will become a chunk of cardboard. Get a couple old cardboard boxes, a roll of duct tape (you just knew I was going to get around to the duct tape, didn’t you?) and a tape measure. Go to the web pages again and get the dimensions for the units you are considering. Make sure that the dimensions you use are the complete external dimensions and that it is with the distribution and discharge and any add-ons you might want. Now go build a box with those same dimensions. If you have a couple units in contention, make as many boxes as you have alternatives. Take them to the boat and find out where they will fit, or if they will fit. This is what is called a “reality check”. Reality can be an ugly thing, sometimes. You may find that the great spot that you thought you had was an inch too small. Or even more disgusting, the great spot is big enough, but there is no way to get it there!
So now you have the perfect location for the unit. In my case, it was in the space forward of the water tank in the V-berth. Now you have to figure out where the rest of the stuff goes. Huh? Yup, there’s more.
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Now you have to find the best location for the overboard for the outlet from the seawater cooling, and a suitable source for the cooling water, and a location for the pump and filter, if they happen to be external to the unit. The biggest problem you may face, unless you are tackling this job while the boat is in its winter storage spot, is where to get the cooling water from. Since my boat was in the water, this would have become a major problem had it not been that I had a three-quarter-inch thru-hull for flushing water and drain for my head sink right beside where I mounted the pump and filter.
One thing you cannot do is tap off of a system that could possible have decreased pressure, such as the water supply for your motor. If you start the motor while the air conditioner is running, the motor could actually pull the water backward through the air conditioner and cause air to be trapped in the system. This could ruin your air conditioner. Be careful using things like sink drains to tap into, also, because the pump could pull the air in from the drain and cause the same problem. In my case, I had a head sink that drained into that line, so I rearranged the piping and put a new overboard in for the sink.
If you happen to be doing this job on the hard, or have a haulout scheduled, you will want to put a new supply thru-hull in. This is a whole other topic. Putting in thru-hulls is easy but takes time to explain.
OK, so now you have the spot for the unit, the pump, the filter, the thru-hulls, a water supply and you are ready, right? Not quite. You still have to figure out where and how you are going to route your vent hoses and put your grills for the supply and return. You need to look closely at the way your boat is constructed. There are areas between the hull and the liner that will allow you to run the duct work, but you will have to be careful because there are other things already running through a lot of those places.
Get a good flashlight and an inspection mirror and start looking for runs where you can get air to where you need it. Since the size of the unit will determine how many outlets you are going to have, revisit your chosen system to see how many paths you need. If you have never pulled all the panels off and gone digging in the hidden areas of your boat, this will be an experience for you. You are probably going to end up doing some cutting, so also consider what tools you are going to be using. I found a Dremmel tool, or Roto-zip to be invaluable. You will also be needing a scroll saw for mounting your vents. As daunting as this is starting to sound, it really isn’t. Just make sure of what is on the other side of what you are cutting through!
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Now that you have all this figured out (you have been taking notes of where everything needs to go, haven’t you?) you can take a look around and figure out where the thermostat can be mounted. You need to be careful with this one. You don’t want it real close to a vent, you don’t want it close to a window or hatch, and you don’t want it close to any other heat source. An interior bulkhead or cabinet is probably the best place. You want it accessible, but not in the way. Last but not least, it is time to look at the electrical demands of this new system. You are going to be placing a pretty hefty load on your AC (electrical) system. You don’t want to run an extension cord to this thing! You are going to have to put in a serious chunk of wire to feed this thing, and with all that power, you need to protect it, too. You will want to tap into your shore power feeder line and put an in-line GFCI type breaker of the right size. The specifications for the breaker and the size of the wire should be provided by the manufacturer. If you are not certain of yourself when it comes to electricity, don’t try this by yourself. This is the one part of the project that you might want to call for help with.
So now you have the project all mapped out. You know the size of the unit you need, you have the spot picked out, you know where the support equipment will be located and where the ductwork needs to be run. You have a location for the thermostat, and have even figured out what wire needs to be run and where to hook it up. You have figured out what tools you will need, drawn a detailed plan, and know what other equipment you are going to need to get your air conditioner up and running. Have you figured out yet how long it is going to take you to do it? Whatever your estimate is, multiply it by two and change to the next higher increment of time. If you figure two hours, you are probably looking at four days. In all seriousness, don’t underestimate the time it will take or the effort that it is going to involve. You are going to find yourself in positions you haven’t imagined since high school gym class. Do not get in a rush. If you do, you will get frustrated and end up breaking something, possibly you.
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They say that Positive Planning Prevents Poor Performance. This is one of those cases. Take your time and figure out the project before you pick up the first tool. Think about what could go wrong and then make contingencies. Walk through each step of the procedure in your head. Keep detailed notes on how you are going to do things and then go back and re-read them to make sure they make sense. This pre-planning will also allow you to assemble all the tools and supplies you will need before you make the trip to the boat. The closest hardware store or marine shop is a long ways away from wherever you are. When I installed our air conditioner, I had planned for three weeks and it took me two days to do it. I only ended up making one emergency Wal-Mart run when my trusty old Dremmel died.
This is a task that will end up being one of the most challenging, but most rewarding efforts you will undertake. You will come out of it with a great degree of self-accomplishment, not to mention a much nicer place to relax while everybody else is roasting in front of a small fan. Pass me that jacket, please! It’s chilly in here!
Scott and his wife Clare have spent many hours refurbishing Double Dutch, since they bought her a year and a half ago. She is a 1982 Catalina 30 with a standard rig, shoal draft keel, and a traditional interior.
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