Lennox LGM092U - Installation and Charging Procedures; Unit Placement and Installation Guidelines; Refrigerant Charging Procedures

Page 36
II-PLACEMENT AND INSTALLATION
Make sure the unit is installed in accordance with the instal
lation instructions and all applicable codes. See acces
sories section for conditions requiring use of the optional
roof mounting frame (C1CURB10).
III-CHARGING
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, re
claim 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:
FIGURE 27
REFRIGERANT STAGES
TRADITIONAL FIN/TUBE COIL
1
2
(BOTH FANS ARE ENERGIZED
WITH A Y1 DEMAND)
CONDENSER COIL
STAGES 1 & 2
EVAPORATOR
COIL STAGE 1
EVAPORATOR
COIL STAGE 2
B4
B5
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 > COOL 4
2- Use a thermometer to accurately measure the outdoor
ambient temperature.
3- Apply the outdoor temperature to tables 11 through 18
to determine normal operating pressures. Pressures
are listed for sea level applications at 80
5F dry bulb and
67
5F wet bulb return air.
4- Compare the normal operating pressures to the pres
sures 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 refriger
ant to the system.
S Add or remove charge in increments.
S 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 11 581027-01
LGM/LCM092U No Reheat
Outdoor
Coil
Entering
Air Temp
CIRCUIT 1 CIRCUIT 2
Dis
charge
+
10 psig
Suction
+
5 psig
Dis
charge
+
10 psig
Suction
+
5 psig
655 F 252 140 269 137
755 F 293 143 311 139
855 F 335 146 354 142
955 F 382 148 403 144
1055 F 434 150 454 147
1155 F 490 153 508 150
TABLE 12 581028-01
LGM/LCM092U Reheat
Outdoor
Coil
Entering
Air Temp
Circuit 1 Circuit 2
Dis
charge
+
10 psig
Suction
+
5 psig
Dis
charge
+
10 psig
Suction
+
5 psig
655 F 258 140 269 136
755 F 301 139 308 137
855 F 344 141 349 139
955 F 392 143 398 142
1055 F 445 145 447 144
1155 F 504 148 501 147
TABLE 13 581029-01
LGM/LCM102U No Reheat
Outdoor
Coil
Entering
Air Temp
Circuit 1 Circuit 2
Dis
charge
+
10 psig
Suction
+
5 psig
Dis
charge
+
10 psig
Suction
+
5 psig
655 F 256 140 259 139
755 F 294 143 300 141
855 F 333 147 341 143
955 F 381 149 388 146
1055 F 433 151 438 149
1155 F 487 155 491 153