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B-Cooling Components
circuits consisting of one compressor, one condenser coil,
Four draw-through type condenser fans are used in
fans are used in LGM210, 240 and 300 units.
-
stalled economizer. All units use an intertwined eveapora-
tor. Each evaporator uses a thermostatic expansion valve
as the primary expansion device. Each evaporator is also
each compressor is protected by a crankcase heater, high
pressure switch and low pressure switch.
1-Compressors B1, B2, B13, B20
compressors and LGM210, 240 and 300 use four com-
pressors. Compressor capacity may vary from stage to
stage. In all cases, the capacity of each compressor is
added to reach the total capacity of the unit. See “SPECI-
FICATIONS” and “ELECTRICAL DATA” (table of contents)
WARNING
Electrical shock hazard. Compressor must be
grounded. Do not operate without protective cover
over terminals. Disconnect power before removing
protective cover. Discharge capacitors before
servicing unit. Failure to follow these precautions
could cause electrical shock resulting in injury or
death.
Each compressor is energized by a corresponding com-
pressor contactor.
NOTE-Refer to the wiring diagram section for specic unit
operation.
If a compressor replacement is necessary, call 1-800-453-
IMPORTANT
Some scroll compressors have an internal vacuum
protector that will unload scrolls when suction
pressure goes below 20 psig. A hissing sound
will be heard when the compressor is running
unloaded. Protector will reset when low pressure
in system rises above 40 psig. DO NOT REPLACE
COMPRESSOR.
2-Crankcase Heaters HR1, HR2, HR5 & HR11
All LGM units use insertion type heaters. Heater HR1 is
installed around compressor B1, heater HR2 compressor
B2, HR5 compressor B13 and HR11 compressor B20.
3-High Pressure Switches S4, S7, S28, S96
S4 all units
S7 all units
S28 all units
The high pressure switches is an auto-reset SPST N.C.
switch which opens on a pressure rise. All units are
equipped with this switch. The switch is located in the
compressor discharge line and is wired in series with the
compressor contactor coil through A55 unit controller or
S4 and S7 are is wired in series with B1 and B2 compres-
B13 and B20 compressor contactors.
opens and the respective compressor(s) is de-energized
(the economizer can continue to operate). When dis-
the pressure switch will close re-energizing the compres-
sor(s).
Main control A55 has a three-strike counter before lock-
ing out. This means the control allows three high pressure
trips per one thermostat demand. The control can be reset
by breaking and remaking the thermostat demand or man-
ually resetting the control.
4-Low Pressure Switches S87, S88, S97, S98
S87 all units
S88 all units
The low pressure switch is an auto-reset SPST N.O.
switch (held N.C. by refrigerant pressure) which opens on
a pressure drop. All units are equipped with this switch.
The switch is located in the compressor suction line. See
-
with the contactor coils through the A55 Unit Controller
The Unit Controller A55 governs the low pressure switches
by shunting the switches during start up until pressure is
stabilized. After the shunt period, the control has a three-
strike counter, during a single thermostat demand, before
the compressor( s) is locked out. The control is reset by
breaking and remaking the thermostat demand or manu-
ally resetting the control.
kPa), (indicating low pressure), the switch opens and the
compressor(s) is de-energized. The switch automatically
Units may be equipped with service valves located in the
discharge and liquid lines. The service valves are manual-
ly operated valves used for service operation.
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