TM 5-6115-593-34NAVFAC P-8-631-34TO-35C2-3-463-217-30. In most installations, intake and exhaust louversare used. Figures 17-6 through 17-9 illustrate a varietyof louver installations which may be used. The use oflouvers requires the opening area to be increased by afactor of 1/4 to 1/2 times that of an unobstructedopening. Where possible, the inlet duct should be onthe shaded side of the building. Care should be taken toprovide adequate unobstructed space outside the outletto prevent development of back pressure andconsequent limiting of outlet air flow. Where possible,the outlet duct should not be exposed to strongprevailing winds, since wind may cancel fan effect andimpair cooling. A duct should be installed between theradiator and the outlet vent to prevent recirculation of airpassed through the radiator, as its effectiveness as aheat exchanger would be diminished. The duct shouldbe installed between the radiator and outlet vent with asfew bends as possible.Figure 17-6. Fixed Louvers for Air Inlet17-31. All units can be fitted with radiator duct flanges.If bends are required, they should be in the form ofgradual sweeps to allow an air flow against minimumrestriction. Increase duct size 1/4 to 1/2 to compensatefor bends. Exhaust duct static pressure should beessentially zero. If a duct is not used, the outlet ventshould be twice the area of the radiator and the unitshould be mounted as close as possible to the outletvent.Figure 17-7. Thermostatically Controlled Louvers17-32. Intake and exhaust ventilation shutters are usedto prevent entry of cold air, which would reduce theambient temperature of the area in which the unit islocated causing difficulty in engine starting. Shuttersalso exclude entry of rain, snow, and insects into thebuilding.Figure 17-8. Exhaust Fan Operated Louvers17-10
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