Exhaust Air System

TM 55-1905-223-24-17

Cooling of Supply Air. To provide cooling, the supply (replenishment) air is routed through the air

conditioning units which operate automatically under the control of compartment thermostats to

maintain set temperatures.

Heating of Supply Air. To provide heating, the supply air is routed through electric heaters

installed in the supply air ducts. The duct heaters operate automatically under thermostatic

control to maintain compartment temperatures. Each duct heater is equipped with an air flow

switch which automatically shuts down the heater when the supply air flow through the heater is

interrupted or stopped. Some ventilated compartments contain electric space heaters which are

self-contained units and are controlled by internal thermostats and manual ON/OFF switches.

Dampers. Certain supply air intakes are equipped with dampers which may be closed to prevent

toxic or dangerous vapors from entering the vessel (see TM 55-1905-223-24-18 for damper

locations).

1-13.

Exhaust Air System. The exhaust system and fans discharge air from the vessel to the atmosphere.

The exhaust fans draw approximately the same volume of air out of the vessel as the supply fans bring

into the vessel. The exhaust system consists of fans and ducting components. There is no heating,

cooling, or filtering of air in the exhaust system. The axial and centrifugal fans in the exhaust system

move the air through the exhaust ducts and discharge it to the atmosphere. Natural exhaust from

staterooms is through door louvers.

1-14.

Recirculation (Return Air) System. The recirculation system consists of air ducts, fans, and air

conditioning units serving the living and working spaces. The recirculation system provides local

filtering and reheating or cooling of air. The recirculation system mixes a calculated quantity of

replenishment air supplied by the supply air fans into the recirculated air and vents an approximately

equal volume of air through the exhaust system in a continuing process. The recirculation system

takes the air already in compartments and recirculates it through ducts, fans, heaters, or air conditioner

cooling coils.

1-15.

Galley Make-Up and Exhaust Air. The galley exhaust fan removes air from the area along with all

cooking smoke and odors. To prevent all air conditioning (cool air) from being sucked out of the area,

this exhausted air must be replenished with fresh air. The exhausted air is replenished with a make-up

supply air fan. This leaves a slight negative pressure on the galley to help prevent migration of cooking

smoke and odors to other parts of the vessel. The fan supplies the fresh air through a duct system

around the perimeter of the exhaust hood.

1-16.

Cooling Cycle and Major Components. The major components in an air conditioning cooling cycle

are the cooling coil, the compressor, the condenser, and the expansion valve (or a capillary tube

assembly in self-contained units). FIGURE 1-3 shows the interface of these components in the basic

cooling cycle. FIGURE 1-3 is a simplified typical arrangement showing major components only.

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