preserving the same margin for extra loads.
This is even more important on larger vessels
with 32,000 Btu air-conditioners or greater.Pumping Seawater
Another critical component of any marine
air-conditioning system is the seawater cool-
ing circuit. Raw seawater is drawn in through
a seacock (sea suction, see Chapter 17),
filtered through a sea strainer, and passed
through the seawater pump (driving this
circuit, and drawing about 1 to 2 amps of AC
electric power). NOTE: Some boats use a DC
electric pump for the seawater cooling circuit.
This means that to turn on the air-conditioner,
the AC electric breaker must be switched on
and the DC breaker must be on for the seawa-
ter pump. This needs to be clearly marked at
the circuit panel and air-conditioning controls.From the seawater pump, the water goes
to the water-cooled condenser/heat-exchanger.
And finally the now-warmed seawater exits
overboard via a through-hull. The seawater
pump should have at least 200 gallons per hour
(757 Lph) of rated flow for every 12,000 Btu.
InKool Kat’s case, this is a minimum of 268
gph or 1,015 Lph.16,000 Btu ÷12,000 Btu= 1. 34
1. 34 × 200 gph= 268 gphor16,000 Btu ÷12,000 Btu= 1. 34
1. 34 × 757 Lph= 1,014 LphA single pump (with sufficient capacity) can
supply two or more air-conditioning-unit
heat-exchangers through a T-fitting or a
manifold (Figure 15-3).PART FIVE: VENTILATION, AIR-CONDITIONING, AND HEATING
Figure 15-3.
Seawater pump
serving two
self-contained
direct-expansion
air-conditioning
units (Courtesy
Marine Air
Systems, Inc.)