Article by Capt. Steve Katz
Keep Your Cool
Next week begins the annual White Marlin Open. If you are fishing... catch'em up! If you are a spectator, enjoy the daily weigh-ins and all the activities during the week.
While most would consider fishing an outdoor activity, the comfort of air conditioning is found on many boats of all sizes. Warm water, warm air and hot engines can make for an uncomfortable day on the water without air conditioning. Marine air conditioning units are similar in operation to your home heat pump system, although the components are very different and of course more expensive. We will review the popular systems, routine maintenance and common problems. These tips will help keep your system operating smoothly and also let you know when to call a professional.
The most popular systems are made by the Dometic Group, the manufacturer of Cruisair, Marine Air, Eskimo Ice and custom freezer/drink box systems, with the DX style system the most common. A DX system is a Direct Expansion system, where the evaporator is in direct contact with the air stream. Larger boats may have chilled/tempered water systems, where the refrigerant cools a circulating water loop that sends cold water to air handlers in the living spaces. A DX system can be all-in-one or a split system, where the compressor is located below deck and connects to the air handler (fan) located in the living area.
Water flow
The most common air conditioning trouble is when the system is not cooling properly due to a lack of seawater cooling. This could be the reason you see the “HI PS” (hi pressure) fault code on your thermostat control. If this happens, you need to check all of the components of the seawater pumping system; this system brings in seawater through a strainer, into a pump, through the air conditioning condenser and out to an overboard outlet. There are many things that can cause reduced water flow such as jellyfish, marine growth, sediment, damaged hoses, defective pump, a clogged strainer and more. Most of these components are readily visible and can be serviced with a minimal amount of tools. Often a simple cleaning and flushing with a garden hose is all that is needed to get your system back to normal and you can flush the system in the opposite direction of the normal water flow to help break up stubborn clogs.
Some of you may have heard that you should put a chlorine tablet into your air conditioning seawater strainer to reduce marine growth. DO NOT do this! Most strainers have plastic components that can be damaged by the chlorine resulting in a failure and possible sinking of the boat. While chemicals are not recommended in most strainers, Bromine tablets are less corrosive and some boaters even drop a copper fitting into the strainer that slowly dissolves, acting like the copper in bottom paint to reduce marine growth. These methods should be used with caution and discussed with the manufacturer of your system to be sure they are safe for your system.
Another popular, heavy duty cleaning method you may have heard about is to flush your seawater system with muriatic acid. Again, this chemical can be too strong and can cause damage to the system components and is not environmentally friendly to discharge into the water. There are a few products made for de-scaling of these systems, such as Barnacle Buster or Rydlyme. These products are usually circulated through the
system for an hour or more, depending on the manufacturers recommendation for your system.
Air Flow
The air conditioning system needs a clean supply of unrestricted air to pass through the evaporator. The evaporator is the part of the system usually located under a seat, bunk or hidden in a closet and looks similar to a car radiator with a fan attached. If you see ice forming on the evaporator, it is often a sign that there is not enough air flow. First check the air filter. Most systems have a washable or replaceable air filter. Second, check for blocked supply or return vents or crushed flexible ducts; the evaporator needs unrestricted air flow to properly cool the air. The supply fan is usually located in this area and should be checked for proper operation.
Refrigerants
Refrigerant (sometimes called Freon, a DuPont trade name) is a man-made compound that changes from a liquid to a gas within the air condition system, transferring heat from one area to another (cabin to the seawater). Government regulations have restricted the use and manufacture of popular refrigerants, resulting in new and often non-compatible refrigerants in the marketplace. Be sure not to mix refrigerants and seek professional advice to find out what refrigerant is best for your system. As part of the Federal Clean Air Act, a technician needs to be licensed to perform work on air conditioning or refrigeration systems and also to purchase refrigerants. Refrigerants are a point of discussion with your service person when a system has a leak, or components need to be replaced. Sometimes a refrigerant re-charge is all that is needed and other times a complete system evacuation, leak testing, cleaning, filter/dryer replacement and re-charge is needed to get your system operating properly.
Condensate
The last tip is to check and clean the condensate drain system. Most boats have a condensate pan under the evaporator with an attached drain hose that can clog and cause water to leak within your boat. During our hot and humid summer, gallons of condensate water can be generated by your air condition system. The condensate drain lines should incorporate a trap or discharge into a sealed sump as to prevent the ingress of carbon monoxide into the living area. ABYC standards do not allow the condensate line to discharge into the engine room.
While there are other components in a marine air condition system, the topics above, cooling water, air flow and refrigerants are the areas most often addressed during a service call.
Captain Steve Katz, ABYC Master Technician, is owner of Steve’s Marine Service serving Annapolis and Ocean City, MD.