They said it couldn’t be done: an air conditioner that runs all night on just batteries and an inverter.By Capt. Bill Pike — January 2003
Take a look at any modern book on outfitting the perfect cruising powerboat, chat up any marine manufacturer or designer, or just page through a mainstream marine magazine these days, and you’ll shortly come up with a consensus: Getting a marine air conditioner to run all night on a midrange cruiser without firing up the genset or plugging into shorepower is an absolute impossibility. Modern, production-type air conditioning units, despite their hip coolness, simply draw too much power for even the most sophisticated inverters to handle long-term, even when teamed up with large battery banks.
Consensus, conshmensus! Back in early June I spent an entire night babysitting a Harley 42 Superstar performance-type sportyacht that, thanks to a custom-built, highly engineered, extra-efficient, 6,000-Btu air conditioning unit onboard, blew just about all the conventional thinking about marine A/C I’m familiar with out of the water.
How? Right off the top, the unit—the brainchild of Miamian Bert Kehren and the handiwork of air conditioning guru Abraham Motro of Avi-Air Marine A/C, also of Miami—is way more conventional than nouveau. It looks like any number of modern production units of the same capacity, at least to the untrained eye, and sports the same type of components—a compressor, evaporator, condenser, water pump, and blower motor. The kicker, however, is that most of these components are just a little more expensive, a little better engineered, and considerably more efficient than the components you ordinarily see on modern mainstream marine air conditioning machines.
While the specific results of my Harley sleepover are pretty darn exciting and indeed may change how cruising people air-condition their boats in the future, understanding these results and their importance requires a little background, starting with a story Kehren authored and sent to PMY early this spring.
It begins with Kehren’s retirement from the world of international corporate management nine years ago, a move that allowed him to establish residence on a canal in North Miami, install the Harley on a lift in his backyard, and begin thinking about how he was really using his boat—or more particularly, his boat’s genset. Eventually he realized that he was operating it only periodically and seldom under much load, at least in part because of his love of peace and quiet. The next step came logically enough. Kehren wondered if there might be a way to downsize or even do away with the genset and toss a battery bank and an inverter into the mix by way of a replacement. The final step? Thanks to some knowledge of electrical engineering, Kehren soon determined that the greatest single power drain onboard the Harley was her oversized, 16,000-Btu air-conditioning system, which drew 16 amps at 110 volts A.C. in cooling mode. “Obviously,” he concluded, “if I was going to rethink my genset situation, I was going to need a more efficient air-conditioner.”
This article originally appeared in the January 2003 issue of Power & Motoryacht magazine.