TM 9-4120-360-14
NORMAL TEMPERATURE - PRESSURE RELATIONSHIPS
NOTE: Dry bulb temperatures are measured with an ordinary thermometer
b. Set-up. Prepare the air conditioner for pressure-testing as directed in the following steps:
(1) Make sure that the fresh air damper is completely closed, and that the evaporator air intake and discharge
grilles are fully open.
(2) Hang inaccurate thermometer directly in front of the evaporator air intake grille to register "dry bulb
return air to unit" temperature.
(3) Hang an accurate thermometer directly in front of the condenser coil guard, making sure that the ther-
mometer is shaded from direct sunlight, to record "outdoor ambient temperature."
(4) Connect a set of Bourdon-type refrigeration pressure gauges or a refrigeration service manifold to the
suction and discharge service valve ports.
(5) If indoor ambient temperature is too low, provide a space heater to raise the "dry bulb return air to unit"
temperature to 80F (27C).
c. Procedure. Perform the pressure test in the following manner:
(1) Turn the selector switch to COOL, and the temperature control thermostat to maximum DECREASE.
(2) Slowly open the suction line and discharge line service valves to which pressure gauges have beencon-
nected.
(3) Let the air conditioner operate for at least 15 minutes in the cooling mode, so that all parts of the system
are stabilized.
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