chilled water. Chilled-water systems (also
termed “tempered-water systems”) are in-
tended for larger vessels—over 75 feet (23 m).
This is the industrial system found in many
commercial buildings and business com-
plexes. When installed in a boat, the chilled-
water system uses a compressor and evapora-
tor located in the machinery compartment to
cool water (the chilled water), which is then
pumped around the boat to air handlers in the
cabin spaces. In this case, the air handlers are
not evaporators. The evaporator is back in
the machinery space, where it chills the
water. Unless you’re dealing with a 75-footer
(23 m) or up, chilled or tempered water is not
for you, which is a bit of a shame because it’s
the quietest air-conditioning available. On the
other hand, the plumbing system for a chilled-
water air-conditioning system is complex.
Initial expense is high, and trained HVAC
technicians are required for installation and
for any major repairs. Many quite large vessels
avoid chilled-water air-conditioning for these
reasons.
Direct-expansion systems (which work
as described earlier) are also available in
two flavors: self-contained direct-expansion
and split direct-expansion. Fundamentally,
they are exactly the same. Indeed, some self-
contained units can be converted to split
types simply by, well, splitting them. The split-
expansion system (Figure 15-1) is nothingChapter 15: Air-Conditioning and Heating
Figure 15-1. Split
direct-expansion
air-conditioner
(Courtesy Marine
Air Systems, Inc.)