OPERATION IN EXTREME HEAT - TM-9-4120-428-140040

TM 9-4120-428-14

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OPERATION IN EXTREME HEAT

These air conditioners are designed to operate in temperatures up to 120 F (49 C) Extra care should be taken to minimize the

cooling mode when operating in extremely high temperatures.

Some of the steps that may be taken include checking all openings in the enclosure, especially doors and windows, to ensure

they are tightly closed; use shades or awnings to shut out direct rays of the sun; limit the use of electrical lights and other

heat-producing equipment; Limit the amount of hot air coming in through the fresh air damper that is essential for

ventilation; clean the filter, mist eliminator, and coils more frequently; and increase the frequency of PMCS.

FILTERS

To maintain the highest capacity of the unit, the evaporator intake filter and fresh air screen should be cleaned weekly or

more often if necessary. Dirty filters reduce the flow of air across the evaporator c oil, thereby reducing the capacity of the air

conditioner.

GUARDS AND LOUVERS

Keep all guards and louvers clean and free of any obstructions to maintain full airflow through the air conditioner. Ensure the

condenser louver in the rear of the unit is open.

COILS

Clean evaporator and condenser coils as frequently as necessary to prevent dirt or other matter from obstructing the airflow.

CAUTION

Do not disturb electrical wiring that has been exposed to extremely low temperatures.

Both the wires and the installation brittle and are easily broken.

OPERATION IN EXTREME COLD

The air conditioner is designed to work in HEAT mode when outside temperatures are down to 50 F (-45 C), and in the

COOL mode when outside temperatures are down to 0 F (-18 C). Extra care should be taken to minimize the heating mode

when operating in extremely low temperatures. Some steps that may be taken include checking all of the openings in the

enclosed, especially doors and windows, to ensure they are secure; Open shades and awnings on the south-facing side of the

enclosure to permit entry of direct rays of the sun; Limit the amount of cold air entering in through the fresh air damper that

is essential for ventilation.

NOTE

It is recommended to weather strip the installation of storm doors and windows, if

appropriate, when running at extremely LOW temperatures and for extended periods of

time.

Before attempting to start the unit in COOL mode, or when fresh air is being used during

the HEAT mode, roll up the canvas cover and ensure all exposed air openings are clear of

ice and snow.

When the unit is to be used at low temperatures in the COOL mode, jump the low

refrigerant pressure cutout switch. Notify supervisor.

OPERATION IN DUSTY OR SANDY CONDITIONS

Dusty and sandy conditions can seriously reduce the efficiency of the air conditioner by clogging the air filter, mist

eliminator, and coils. This will restrict the volume of airflow. Accumulation of dust or sand in the condenser coil and/or in

the compressor compartment may cause overheating of the refrigeration system. Dust or sand may clog the condensation trap

and water drain lines.

Clean filters, mist eliminators, coils, and all other areas of dust and sand accumulation. In extreme conditions, clean filters

daily. Limit the amount of dust and sand entering through the fresh air damper essential for ventilation. Roll down and secure

the fabric cover on the back of the cabinet during periods of shutdown and increase the frequency of PMCS.

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