Starting And Operating Instructions For Cooling

TM 9-4120-428-14

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Starting And Operating Instructions For Cooling - Continued

9. Check for maximum ventilation with fresh air by turning the fresh air damper control wheel to open (down), and then

adjust the blades in the return air louver to close them. Check the fresh air inlet located on the lower left corner of the

back of the unit using a paper streamer or other method to be sure that air is being drawn in.

NOTE

To maximize the introduction of fresh air into the shelter, a door or window must be

opened slightly to prevent an overpressure condition that would restrict airflow.

The TEMPERATURE SELECTOR (thermostat) control has an effective functional range

between 60F and 90F (16C and 32C).

10. Turn the TEMPERATURE SELECTOR (thermostat) knob to the full WARMER (clockwise) position and then turn the

MODE SELECTOR switch to LOW HEAT. Place your hand in the airflow from the conditioned air supply louver and

feel for a temperature rise. When the supply air temperature has reached a relatively stable level, turn the MODE

SELECTOR switch to HIGH HEAT and feel for a further temperature rise. Next, turn the TEMPERATURE

SELECTOR thermostat control knob to the fully COOLER (counterclockwise) position. Feel that supply air temperature

drops to approximately the same relatively stable level previously noted in LOW HEAT. Finally, turn the MODE

SELECTOR switch to LOW HEAT and feel the discharge air temperature drop to ambient level (room temperature).

CAUTION

If a knocking or pounding noise is heard when the compressor starts, immediately turn

the MODE SELECTOR out of the COOL position. Leave input power connected and

wait at least two hours before attempting another start in COOL mode.

11. Turn the TEMPERATURE SELECTOR control knob to the WARMER (clockwise) position, then turn the MODE

SELECTOR switch to COOL. Note that the evaporator and condenser fans start immediately and that the compressor

starts approximately 30 seconds later. Hold your hand in the airflow from the conditioned air supply louver; there should

be no change in temperature. Now turn the TEMPERATURE SELECTOR control knob to the COOLER

(counterclockwise) position and feel the supply air temperature begin to drop almost immediately. Leave controls in the

present position and perform the next check.

CAUTION

Do not operate the air conditioner in the COOL mode if the sight glass has numerous

bubbles going through it or if the indicator color is yellow.

12. After 15 minutes of operation, check the sight glass to determine the refrigerant condition. If the liquid refrigerant

observed in the sight glass has a milky appearance or frequent bubbles appear, the volume of refrigerant could be low

and the system may need to be charged. The sight glass contains an indicator that is sensitive to water moisture. This

indicator changes color in response to the amount of water moisture that may be contained in the refrigerant. Excessive

moisture in the refrigerant may damage or possibly destroy the compressor. If no moisture is present, the i ndicator will

be green. If the moisture content becomes undesirable, the indicator will be greenish yellow. If the moisture content

becomes unacceptable, the indicator will be yellow. If a low charge or unacceptable moisture level is indicated, contact

direct support maintenance to take appropriate action.

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