MODEL PCA090480WH
CHAPTER 2
SERVICE
Section 8: Adjustments
March 2013
2-8
Proprietary/Confidential
Page
57
© 2013 Twist, Inc.
1. Thermostats
The temperature control for both cooling and heating is automatically
controlled and requires no adjustment.
2. Expansion
Valve
Superheat
Each Thermostatic Expansion Valve is thoroughly tested and set at the factory
before shipment. This factory superheat setting will be correct, and no further
adjustment is required for the majority of the applications.
Prior to replacing or repairing the Expansion Valve, turn the valve stem
counterclockwise and count the number of turns allowed before a ratcheting
sound is heard. Record that number for use later. Once a new valve or valve
cartridge is installed, turn the stem counterclockwise until the ratcheting sound
is heard. Now turn the stem clockwise the number of turns recorded above.
This process will set the new valve to factory specifications. When the
adjustment is completed on the valve, always tighten the adjusting stem-
packing nut and replace the seal cap tightly.
To determine superheat of the system:
A.
Measure the temperature of the suction line at the point the bulb
is clamped.
B.
Read the gauge pressure at the suction valve near the
compressor. To this pressure add the estimated pressure drop
through the suction line between bulb location and compressor
suction valve, which is approximately 2 psig. The sum of the
gauge reading and the estimated pressure drop will equal the
approximate suction line pressure at the bulb.
C.
Convert the pressure obtained above to the saturate evaporator
temperature by using the temperature-pressure chart found in the
appendix of this manual.
D.
Subtract the two temperatures obtained in 1 and 3 - the
difference is superheat.
To change the superheat setting:
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