Air Dryers—A-4400 Series Technical Bulletin
11
Ambient Temperature (°F)
E
v
a
p
o
ra
to
r
P
re
s
s
u
re
(
p
s
ig
)
28
26
36
34
32
30
38
40
39
41
42
43
37
35
33
31
29
27
40
50
60
70
80
90
100
110
120
130
Acceptable Operating Zone
Nominal Setting
Figure 5: Evaporator Pressure vs. Ambient Temperature
(Sea Level--No Load Condition)
If the air dryer is used in ambient conditions between 35 and 40
°
F
(2 and 4
°
C) the expansion valve must be adjusted to increase the expansion
valve gauge pressure by 3 psig (21 kPa) to offset a possible freeze-up
condition. This increase in evaporator pressure must be added to the value
determined by the graph in Figure 5 to account for low ambient temperature
effects. At high altitudes and low ambient temperatures, it will be necessary
to add both pressure corrections and readjust the expansion valve. Refer to the
Refrigeration Service section and follow Steps 1 through 5 (readjusting the
expansion valve setting) to properly adjust the expansion valve until the
evaporator pressure is at the adjusted pressure. Operation of the A-4400 in
ambient temperatures below 35
°
F (2
°
C) is not recommended.
Note: If it was necessary to adjust the expansion valve settings and position
the service bypass valve to bypass the air dryer, then return the service
bypass valve to normal mode in order to resume operation. Also, if
the pressures were changed from the normal settings, indicate the
changes on the air dryer to facilitate future service.
Low Ambient
