Lennox LHT078H

Page 20
C-Refrigerant Charge and Check - Fin/Tube
WARNING-Do not exceed nameplate charge under
any condition.
This unit is factory charged and should require no further
adjustment. If the system requires additional refrigerant,
reclaim the charge,
evacuate the system, and add
required nameplate charge.
NOTE - System charging is not recommended below
60°F (15°C). In temperatures below 60°F (15°C) , the
charge must be weighed into the system.
If weighing facilities are not available, or to check the
charge, use the following procedure:
1-
Attach gauge manifolds to discharge and suction lines.
With the economizer disabled, operate the unit in
cooling mode at high speed using the following mobile
service app menu path:
SERVICE > COMPONENT TEST > COOLING >
COOLING STAGE 3
2- Use a thermometer to accurately measure the
outdoor ambient temperature.
3- Apply the outdoor temperature to tables 4 through 8
to determine normal operating pressures.
Pressures are listed for sea level applications at
80
5F dry bulb and 675F wet bulb return air.
4- Compare the normal operating pressures to the
pressures obtained from the gauges. Minor
variations in these pressures may be expected due to
differences in installations. Significant differences
could mean that the system is not properly charged
or that a problem exists with some component in the
system. Correct any system problems before
proceeding.
5- If discharge pressure is high, remove refrigerant from
the system. If discharge pressure is low, add
refrigerant to the system.
 Add or remove charge in increments.
 Allow the system to stabilize each time
refrigerant is added or removed.
6- Use the following subcooling method along with the
normal operating pressures to confirm readings.
TABLE 4 581118-01
LHT/LDT078
Outdoor
Coil
Entering
Air Temp
CIRCUIT 1 CIRCUIT 2
Dis
charge
+
10 psig
Suction
+
5 psig
Dis
charge
+
10 psig
Suction
+
5 psig
65 °F 244 132 236 145
75 °F 281 134 271 146
85 °F 322 136 309 148
95 °F 366 138 354 150
105 °F 415 139 399 152
115 °F 464 141 449 154
TABLE 5 581119-01
LHT/LDT092
Outdoor
Coil
Entering
Air Temp
Circuit 1 Circuit 2
Dis
charge
+
10 psig
Suction
+
5 psig
Dis
charge
+
10 psig
Suction
+
5 psig
65 °F 250 139 253 139
75 °F 286 140 291 140
85 °F 326 141 331 141
95 °F 370 142 376 143
105 °F 417 144 426 146
115 °F 468 146 481 148
TABLE 6 581120-01
LHT/LDT102
Outdoor
Coil
Entering
Air Temp
Circuit 1 Circuit 2
Dis
charge
+10 psig
Suction
+
5 psig
Dis
charge
+10 psig
Suction
+
5 psig
65 °F 245 139 258 130
75 °F 283 142 296 133
85 °F 321 141 336 133
95 °F 370 146 389 138
105 °F 417 148 435 141
115 °F 469 151 492 144
TABLE 7 581121-01
LHT/LDT120
Outdoor
Coil
Entering
Air Temp
Circuit 1 Circuit 2
Dis
charge
+
10 psig
Suction
+
5 psig
Dis
charge
+
10 psig
Suction
+
5 psig
65 °F 248 126 256 125
75 °F 285 128 293 127
85 °F 326 130 334 129
95 °F 372 132 379 131
105 °F 420 135 426 134
115 °F 475 139 477 137
TABLE 8 581122-01
LHT/LDT150
Outdoor
Coil
Entering
Air Temp
CIRCUIT 1 CIRCUIT 2
Dis
charge
+
10 psig
Suction
+
5 psig
Dis
charge
+
10 psig
Suction
+
5 psig
65 °F 255 125 252 112
75 °F 295 128 293 124
85 °F 337 130 335 130
95 °F 382 134 381 133
105 °F 430 136 427 135
115 °F 485 139 476 137