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F-Compressor Controls
See unit wiring diagram to determine which controls are
used on each unit.
1-
Units Equipped With All-Aluminum Coils -
High Pressure Switch (S4, S7)
The compressor circuit is protected by a high
pressure switch which opens at 610 psig + 15 psig
(4206 kPa + 103 kPa) and automatically resets at 475
psig + 15 psig (3 103 kPa).
2-
Units Equipped With Traditional Fin/Tube Coil -
High Pressure Switch (S4) (S7 on 092H, 102H, 120H,
150H only)
The compressor circuit is protected by a high
pressure switch which opens at 640 psig + 10 psig
(4413 kPa + 70 kPa) and automatically resets at 475
psig + 20 psig (3 138 kPa).
3- Low Pressure Switch (S87) (S88 on 092H, 102H,
120H, 150H only)
The compressor circuit is protected by a loss of
charge switch. Switch opens at 40 psig + 5 psig (276
+ 34 kPa) and automatically resets at 90 psig + 5
psig (621 kPa + 34 kPa).
4- Crankcase Heater (HR1, HR2)
Compressors have belly band compressor oil heaters
which must be on 24 hours before running
compressors. Energize by setting thermostat so that
there is no cooling demand, to prevent compressor
from cycling, and apply power to unit.
5- Low Ambient Pressure Switch (S11) (S84 on 092H,
102H, 120H, 150H only)
Switch maintains adequate discharge pressure by
de-energizing condenser fans when liquid pressure
falls below 240 psig +10 (1655 kPa+69). S11 is
installed in the liquid line. Switch closes to energize
condenser fan when pressure rises to 450 psig +10
(3 69).
Units Equipped With Two Fans -
The Unit Controller de−energizes condenser fan 2
when outdoor temperature drops below 55°F (13°C).
Fan 1 will continue to cycle with liquid pressure.
Units Equipped With Three Fans -
The Unit Controller de−energizes condenser fan 2
and 3 when outdoor temperature drops below 55°F
(13°C). Fan 1 continues to operate based on outdoor
ambient temperature and liquid pressure.
6- Freezestats (S49, S50)
Switches de-energize compressors when evaporator
coil temperature falls below 29°F (-2°C) to prevent
evaporator freeze-up. Switches reset when
evaporator coil temperature reaches 58°F (15°C).
7- Thermal Protector (S5, S8)
The compressors used on 094U, 122U and 152U
units are protected by an external temperature
switch. The n.c. switch opens at 248°F + 9 (120°C +
5) and automatically resets at 169°F + 18 (76°C + 10).
8- Pressure Transducer (A185)
The compressor circuit on 094U, 122U and 152U
units are monitored by the Unit Controller via the
suction pressure transducer.
9- Compressor Temperature sensor (RT37, RT38)
The compressor circuit on models 094U, 122U and
152U units are monitored by the Unit Controller via
compressor bottom thermistors.
