Ships without central air conditioning may use self-contained air-conditioning units. NAVSEA approval is required.

A self-contained air-conditioning unit is simply the type of air conditioner you see installed in the windows of many homes. All that is required for installation is to mount the proper brackets for the unit case and provide electrical power.

These units use nonaccessible hermetically sealed compressors (motor and compressor are contained in a welded steel shell). For this reason, shipboard maintenance of the motor-compressor unit is impractical. The type of thermal expansion valve used in these units is preset and nonadjustable. However, a thermostat and fan speed control are normally provided for comfort adjustment.

HEATING EQUIPMENT

Ventilation heaters are installed in ventilation ducting to heat spaces in cold weather and to control humidity. Aboard Navy surface ships, heating a space is accomplished either by steam or by electric duct heaters, convection heaters, or unit heaters. Duct heaters are installed in mechanical supply ducts as preheaters or reheaters, and in recirculation ducts as reheaters. (Fig. 17-11 illustrates a steam duct heater.) Convection heaters (fig. 17-12) are generally used in spaces that are not served by mechanical supply systems or recirculation systems. Unit heaters (heating coils with their own fan) are used where the heat load is larger than can be adequately handled by convection heaters. All of these heaters can be used with steam pressures up to 150 psi. Electric heaters are simply banks of heating elements installed in the airflow of a ventilation system.

Figure 17-12.-Convection heater (cutaway view).

Figure 17-11.-Steam ventilation heater.