Page 14
Charging Using Normal Operating Pressures
and the Approach Method
TXV Systems – Outdoor Temp. >
65F (18C)
The following procedure is intended as a general guide and
is for use on expansion valve systems only. For best results,
indoor temperature should be 70°F (21°C) to 80°F (26°C).
Monitor system pressures while charging.
1 − Record outdoor ambient temperature using a digital
thermometer.
2 − Attach high pressure gauge set and operate unit for
several minutes to allow system pressures to stabilize.
3 − Compare stabilized pressures with those provided in
table 5, Normal Operating Pressures." Minor varia-
tions in these pressures may be expected due to differ-
ences in installations. Significant differences could
mean that the system is not properly charged or that a
problem exists with some component in the system.
Pressures higher than those listed indicate that the
system is overcharged. Pressures lower than those
listed indicate that the system is undercharged. Verify
adjusted charge using the approach method.
Approach Method
4 − Use the same digital thermometer you used to check
the outdoor ambient temperature to check the liquid
line temperature.
5 − The difference between the ambient and liquid temper-
atures should match values given in table 4. If the val-
ues don’t agree with the those in table 4, add refriger-
ant to lower the approach temperature, or recover re-
frigerant from the system to increase the approach
temperature.
Table 4
Approach Values
Model Number
Liquid Temp. Minus Ambient
Temp. °F (°C)
HS27−024 5 + 1 ( 3 + .5)
HS27−030 5 + 1 ( 3 + .5)
HS27−036 6 + 1 ( 3.3 + .5)
HS27−042 7 + 1 ( 3.9 + .5)
NOTE − For best results, the same digital thermometer should be
used to check both outdoor ambient and liquid temperatures.
IMPORTANT
Use table 5 to perform maintenance checks. Table 5
is not a procedure for charging the system. Minor
variations in these pressures may be due to differ-
ences in installations. Significant deviations could
mean that the system is not properly charged or that
a problem exists with some component in the system.
See table 5.
Table 5
Normal Operating Pressure
s
HS27−024 HS27−030 HS27−036 HS27−042
u
oor
Temp. (F)
Liq. + 10
psig
Suct. + 5
psig
Liq. + 10
psig
Suct. + 5
psig
Liq. + 10
psig
Suct. + 5
psig
Liq. + 10
psig
Suct. + 5
psig
65 135 78 139 79 136 76 141 82
75 159 79 163 80 160 77 166 82
85 186 80 180 81 188 80 185 82
95 216 82 219 83 217 80 226 85
105 249 83 252 84 251 82 257 85
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