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glare-heat-personIt seems that there's an ongoing quest in some circles for the holy grail of boating comfort: 12 volt air conditioning. Yet few seem to fully appreciate the benefits of the more practical, but far less complex and substantially less expensive alternative: 115v AC air conditioning powered by a DC source through an inverter. Many boats these days already have inverters installed, and if not, there's a wide range of inexpensive models available that are suitable for powering small air conditioners.

This post will focus on small air conditioning systems that are suitable for sleeping cabins or for small boat applications. With a small unit, the DC current draw is low enough that they can usually be powered by an engine alternator whenever the engine is running, as well as from the batteries when required. Of course, any sized air conditioner can be powered by batteries through an inverter, it is just a matter of practicality.

To better understand the differences between the two concepts, some comparisons are shown below between the Climma Compact 4,200 Btu 115v AC unit and the Dometic Cuddy II 3,500 Btu 12v DC model.

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You want to go for an overnight boat adventure, but it's hot out there, even on the water. During the day, no problem, there is wind, a bimini, swimming to keep you cool, but at night, when you want to sleep, the thought of that hot, humid cabin can be a deal killer.

Solution: a small air conditioning system that is perfect for a sleeping cabin, to lower the cabin's humidity and temperature.

With a small 115v unit, the current draw is low enough that it can usually be powered by an engine alternator during the day when the engine is running and then from the batteries, through an inverter, at night. You may not need a generator, if you choose the right air conditioning unit.

There are also 12v air conditioning units available, but only one that is really worth looking at, and even then, the cost may make the venture unattainable.

To better understand the choices, let's compare two units:

vacuum-pumpUnless other actions are also taken, using a vacuum pump to evacuate a R134a refrigeration system will almost certainly not result in a permanent resolution to particle or moisture blockages. This is true no matter how deep the vacuum or for how long the vacuum pump is run.

strong>Moisture issues - Back in the day, when refrigeration systems used good old ozone-gulping refrigerant R12 and mineral oil in the compressor, moisture could be removed from the entire system, including the oil, simply by hooking up a vacuum pump and taking the system down into a pretty deep vacuum. Any moisture would evaporate out of the oil at this low pressure, and find its way out of the system as a vapor via the vacuum pump. Skip forward to the present day, and we now use more environmentally friendly refrigerants such as R134a which requires a synthetic oil for the compressor.

The Danfoss/Secop BD 35 and BD 50 compressors are supplied filled with a polyolester (POE) oil, which is extremely hygroscopic i.e. it will grab hold of any passing spec of moisture and won't let it go easily. In fact, the oil forms a molecular bond with the moisture, and no matter how deep a vacuum is applied, or for how long, those pesky moisture molecules will remain trapped in the oil unless another element is brought into play, and that element is heat.

keel cooler trilogy 1024x341Frigoboat's Keel Cooler, installed on over 40,000 vessels worldwide, offers water-cooled heat exchange for your refrigeration system without the use of a pump. This means no strainers to clean, no noise, and little maintenance.

The Keel Cooler is embedded in sintered bronze, which is primarily copper, making it naturally anti-fouling. Add to this the fact it is warm to the touch when in operation means there should be little sea growth on it.

However, in some areas the water is rich with algae and other sea life and a build-up can occur. Not a problem. Simply use a stiff, nylon brush or green scrubber pad to wipe the accumulation off the keel cooler. Pesky barnacles may require a plastic scraper, but please resist the temptation to use a metal scraper or wire brush. Both of these devices could harm the sintered bronze coating and potentially the embedded cuper nickel tubing containing the refrigerant.

There is quite a collection of Eco-friendly "Barnacle Buster" products that can be used to help dislodge crustations, but please read the instructions carefully.

If you have continued issues with excessive growth on your keel cooler, a single coat of anti-fouling paint can be applied with little to no noticeable loss of performance. Bear in mind, though, that you can then no longer use your keel cooler as a grounding plate for an SSB or other radio device.

Rest assured, your keel cooler should last the life of your Frigoboat system.

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