Lennox KGC Series Unit Information page 17

1-Compressors B1 and B2
All units use two scroll compressors. 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 "SPECIFICATIONS" 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
coverover 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
compressor contactor.
NOTE-Refer to the wiring diagram section for specific unit
operation.
If Interlink 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
unloaded. Protector will reset when low pressure
in system rises above 40 psig. DO NOT REPLACE
COMPRESSOR.
2-Thermal Protectors S5, S8
Some compressors have thermal protectors located on
top of the compressor. The protectors open at 248°F + 9°F
(120°C + 5°C) and close at 169°F + 18°F (76°C + 10°C).
3-Freezestats S49 and S50
Each unit is equipped with a low temperature switch
(freezestat) located on a return bend of each evaporator
coil. S49 (first circuit) and S50 (second circuit) are located
on the corresponding evaporator coils.
Freezestats are wired in series with compressor
contactors. Each freezestat is a SPST N.C. auto-reset
switch which opens at 29°F + 3°F (-1.7°C + 1.7°C) on
a temperature drop and closes at 58°F + 4°F (14.4°C +
2.2°C) on a temperature rise.
To prevent coil icing, freezestats open during compressor
operation to temporarily disable the respective compressor
until the coil temperature rises.
If the freezestats are tripping frequently due to coil icing,
check the airflow/filters, economizer position and unit
charge before allowing unit back in operation. Make sure
to eliminate conditions which might promote evaporator
ice buildup.
4-High Pressure Switches S4 and S7
The high pressure switch is a manual reset SPST N.C.
switch which opens on a pressure rise.
S4 (first circuit) and S7 (second circuit) are located in the
compressor discharge line and are wired in series with the
respective compressor contactor coils.
When discharge pressure rises to 640 ± 12 psig (4413 ±
138 kPa) (indicating a problem in the system), the switch
opens and the respective compressor is de-energized
(the economizer can continue to operate).
5-Low Ambient Kit (field installed)
The Low ambient kit is field installed. This kit has a
temperature switch and a head pressure controller. This
kit allows mechanical cooling operation by maintaining
liquid pressures at low outdoor temperatures, by stopping
or slowing the outdoor fans.
Liquid line pressure switches (A188 & A189) will de-
energize condenser fans below 355 psig, preventing low
ambient operation. Liquid line pressure transducers are
installed to convert the pressure to an analog signal which
is sent to the head pressure controller (A190). The head
pressure controller provides a variable output which slows
condenser fan operation at lower ambient temperatures
(A190 terminal M to K10 normally open contacts). Lower
fan speeds increase the liquid line pressure, allowing
operation above 355 psig.
6-Crankcase Heaters HR1, HR2
150S units use insertion-type heaters. Heater HR1 is
installed around compressor B1 and heater HR2 is installed
around compressor B2. Crankcase heater wattage varies
by compressor manufacturer.
7- Filter Drier
Units have a filter drier located in the liquid line of each
refrigerant circuit at the exit of each condenser coil. The
drier removes contaminants and moisture from the system.
8- Condenser Fans B4, B5
See SPECIFICATIONS tables at the front of this manual
for specifications of condenser fans used in all units. All
condenser fans used have single-phase motors. The fan
assembly may be removed for servicing and cleaning.
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