Cool Currents: A/C on DC?
Practical Sailor published articles on air-conditioning (A/C) in the December 2000 and January 1, 2001 issues.
Shortly thereafter we received some letters from readers asking if we'd had a chance to evaluate a new DC-powered air-conditioning system called Cool Currents. We had not, so we got in touch with Frank Schooley, the machine's inventor and purveyor, and he kindly sent one along.
With so many boats spending so much time in marinas, the demand for onboard A/C has grown rapidly in recent years, and manufacturers have responded with a number of systems, the most common of which are self-contained units that sit in hatches. Their major drawback is that they draw lots of AC power. This either limits them to marina use only, or demands an onboard genset.
The Cool Currents machine is intended to be an alternative to all that. It should be noted that it is not marketed as a head-to-head competitor against AC-powered systems for sheer cooling power. In that case it would surely lose. In a bang-for-the-watt competition, though, it has several advantages, some of which are constant (it's light, simple, low-powered, and less expensive), and some variable according to conditions.
Unlike standard marine-use A/C machines, which use electric motor-driven refrigeration compressors, Cool Currents operates on the simple principle of heat exchange. It uses hoses to pull cool water up from below the surface and through a heat exchanger (a radiator) in the unit. Two simple muffin fans pull the warm cabin air through the radiator and pump the cooler air out the other side. That's that. The efficiency of the machine depends entirely on sub-surface water temperatures and on the cabin temperature it's working with.
On a hot day in early September we took the Cool Currents machine to a nearby marina and tried it out on a friend's Pearson 303, which was locked up tight in the sun. It was quick to set up—the dual hoses are taken out of the base of the plastic case and uncoiled. The deep-water hose, which has a strainer at the bottom, is attached via a plastic quick-connector below the submersible pump, and let down as far as possible into the cooler water layers, but not all the way to the bottom. The pump is submerged nearer the surface; it should have a depth of at least a couple of feet to compensate for the boat's rolling, and has a maximum head depth of 9 feet. In shallow water the strainer can be attached directly below the pump, but there are various combinations of hose lengths that will allow the suction to go down as far as about 20 feet. In general, the deeper the water, the better the machine will perform.
While set-up was quick, it did involve a bit of wrestling with the hoses, which tend to retain their coiled shape, and a lot of wrestling with the plastic housing, whose halves tended to come apart and not fit back together without a lot of TLC. The hoses needed to be lashed in a couple of places to keep them from infesting the cockpit, and to keep them secure at the toerail. It would be relatively easy for a boatowner to develop a system with markings on the hoses and pre-installed lashings to improve set up and reduce clutter.
Our test notes on the previous page will speak for themselves. If Cool Currents had been billed as a full-on A/C unit, we would have been disappointed; as it was, we'd call it a modest success: It was a lot better than a fan if you stood right in front of it. It drew little power. It was very nearly silent. And it cooled the cabin a few degrees while pulling water from the bottom that wasn't markedly colder than the surface water.
The quality of working components—pump, fans, hoses, switches, gauge, and connectors—is very good.The housing, however, is weak and frustrating to work with; it should be more robust, with strong hinges, even if it adds a couple of pounds of weight.
The current price of Cool Currents is $695—about half what a typical self-contained AC-powered marine air-conditioner costs.
Contact- Cool Currents, Box 314, Matlacha, FL 33993, 941-283-3978, www.coolcurrents.net.
Also With This Article
Click here to view "Test Notes."