Notes on Refrigeration
As with air-conditioning, the widespread
installation of refrigeration is a relatively new
development. Thirty or forty years ago, almost
all boats had only iceboxes. A simple icebox
has plenty to recommend it: no moving parts,
nothing to go wrong. For many dayboats and
small cruisers, using an icebox makes more
sense than installing refrigeration. After all,
refrigerators basically work the same way air-
conditioners do—which is to say they have
many moving parts and require power.Types of Refrigerators
On boats, refrigerators come in four standard
types:1 .Portable cooler-freezers.These
self-contained portable units run on
12 volts DC, 120 volts AC, or both.PART FIVE: VENTILATION, AIR-CONDITIONING, AND HEATING
Figure 15-4.
Typical air-
conditioner duct-
ing (Courtesy
Marine Air
Systems, Inc.)
Tons of Air-Conditioning
You’ll often hear air-conditioning techni-
cians referring to the size of air-
conditioning units in tons. A ton of air-
conditioning is simply another measure of
cooling (really heat transfer) capacity.
We’ve seen that the Btu is the British ther-
mal unit, or the quantity of heat required
to raise the temperature of 1 pound of
water by 1 degree Fahrenheit.
By comparison, a thermodynamic ton
(as opposed to weight or mass) is the
amount of energy required to melt a
1-ton block of freshwater ice in 24 hours.
One ton is roughly equal to 12,000 BTUs
or 3.51 kW. Thus, the 16,000 Btus (4.7 kW)
installed in Kool Katis a 1.3-ton air-
conditioning system.