Trane PTEC-070 Operation & Maintenance Manual page 29

PTEC-M-1A
Refrigeration
System
Cooling Performance Test
The following temperature must be
recorded for the cooling
performance test:
a. Dry bulb temperature of return air
at conditioner. Locate
thermometer as illustrated.
b. Dry bulb temperature of discharge
air. Thermometer has to be
located as illustrated on previous
page.
c. The dry bulb thermometer
temperature on the sling
psychrometer should be plus or
minus 1°F within reading obtained
on thermometer in the return air.
Check wet bulb temperature on
sling psychrometer and record
same.
d. After the wet bulb temperature,
dry bulb temperature, and return
air temperature have been
recorded, proceed to calculate the
temperature difference as follows.
e. Subtract temperature obtained in
Step B from temperature obtained
in Step A. The remainder
temperature is used to calculate
from the Cooling Change of
Temperature in Diagnostic Charts.
Example: Assume a PTHC15 unit is
under test and the temperature
readings indicated below were
obtained.
1. Return air D.B. temperature: 80°F,
Step A.
2. Discharge air D.B. temperature:
69°F, Step B.
3. Return air, wet and dry bulb
temperature as recorded in Step
C: Dry Bulb 80°F, Wet Bulb 75°F.
4. In left hand column of Cooling
Capacity Charge headed Dry Bulb,
find the 80° value.
5. In column headed Wet Bulb find
the 75° value and find the value "8
-13" in the cooling range column
under the Model "PTHC15".
This data shows that the
temperature of the air passing
through the cooling coil is reduced at
least 8°F but not more than 13°F. This
example unit is operating normally
for the existing conditions.
For the example unit under test, the
temperature difference was 11°F
(80°F, return air, minimum 69°F
discharge air). Since the value is
within the listed cooling range 8 - 13,
this unit is considered to be
operating normally.
Important Note:
Never test operation without the
unit in the wall sleeve. A serious
change in design specifications for
air movement through the
evaporator and condenser
compartments, causing the fan
motor to over heat and the
refrigeration system to become
unbalanced will occur when the unit
is not installed in the wall sleeve.
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