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B-Cooling Components
Model L ultra high efficiency units use independent cooling
circuits consisting of one compressor, one condenser coil,
and one evaporator coil per circuit. See figures 7 and 6.
Four draw-through type condenser fans are used in
LCM156, 180 units and six draw-through type condenser
fans are used in LCM210, 240 and 300 units.
Cooling may be supplemented by a factory‐ or field‐in
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
equipped with enhanced fins and rifled tubing. In all units
each compressor is protected by a crankcase heater, high
pressure switch and low pressure switch.
1-Compressors B1, B2, B13, B20
All units use scroll compressors. LCM156 and 180 use 3
compressors and LCM210, 240 and 300 use four compres
sors. 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 “SPECIFICA
TIONS” and “ELECTRICAL DATA” (table of contents) or
compressor nameplate for compressor specifications.
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 ser
vicing 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 specific unit
operation.
If a compressor replacement is necessary, call
1-800-453-6669.
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 un
loaded. Protector will reset when low pressure in
system rises above 40 psig. DO NOT REPLACE
COMPRESSOR.
2-Crankcase Heaters HR1, HR2, HR5 & HR11
All LCM units use insertion type heaters. Heater HR1 is in
stalled 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 S96
210, 240, 300
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 com
pressor discharge line and is wired in series with the com
pressor contactor coil through A55 unit controller or A178
compressor 3 and 4 controller. See figure 6.
S4 and S7 are is wired in series with B1 and B2 compressor
contactors and S28 and S96 are wired in series with B13
and B20 compressor contactors.
When discharge pressure rises to 640 ± 10 psig (4413 ± 69
kPa) (indicating a problem in the system) the switch opens
and the respective compressor(s) is de-energized (the
economizer can continue to operate). When discharge
pressure drops to 475 ± 20 psig (3275 ± 138 kPa) the pres
sure switch will close re-energizing the compressor(s).
Main control A55 has a three-strike counter before locking
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
S97 210, 240, 300
S98 all units
The low pressure switch is an auto‐reset SPST N.O. switch
(held N.C. by refrigerant pressure) which opens on a pres
sure drop. All units are equipped with this switch. The
switch is located in the compressor suction line. See figure
6.
S87 and S88 (compressor one and two) and S98 (com
pressor three) ans S98 (compressor 4) are wired in series
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 stabi
lized. After the shunt period, the control has a three‐strike
counter, during a single thermostat demand, before the com
pressor(s) is locked out. The control is reset by breaking and
remaking the thermostat demand or manually resetting the
control.
When suction pressure drops to 40 +
5 psig (276 ± 34
kPa), (indicating low pressure), the switch opens and the
compressor(s) is de-energized. The switch automatically
resets when pressure in the suction line rises to 90 +
5
psig (620 ± 34 kPa).
5-Service Valve (optional)
Units may be equipped with service valves located in the
discharge and liquid lines. The service valves are manu
ally operated valves used for service operation.
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