Page 35
In LGH180H/210 units, S11 (compressor one) is wired to
the Unit Controller (A55) and S84 (compressor two) and
S85 (compressor three) are wired in parallel to the Unit
Controller. In LGH240H/300 units, S11 (compressor one)
and S84 (compressor 2) are wired in parallel to the Unit
four) are wired in parallel to the Unit Controller. In 180U,
240U and 300U models, S11 (compressor 1 and 2) and
S85 (compressor 3 and 4) are wired to unit controller A55.
kPa), the switch opens and the Unit Controller will cycle
condenser fans via the following outdoor fan relays:
K10 and K68 (156H, 180H, 210H, 300)
K152 and K153 (180U, 210, 240, 300 units)
kPa), the switch closes and re-energizes the condenser
fans. The Unit Controller cycles fans based on the low
ambient pressure switch inputs and outdoor ambient tem-
perature.
This intermittent fan operation results in higher evaporat-
ing temperature allowing the system to operate without
icing the evaporator coil and losing capacity.
5-Low Pressure Switches S87, S88, S97, S98
S87 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.
-
tactor coils through the A55 Unit Controller. On ultra high
(compressor three and four) are wired in series with the
contactor coils through the A55 Unit Controller
The Unit Controller A55 governs the low pressure switch-
es 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 re-
set 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
psig (620 ± 34 kPa).
6-Service Valve (optional)
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.
7-Filter Drier (all units)
-
frigerant circuit at the exit of each condenser coil. The dri-
er removes contaminants and moisture from the system.
8-Freezestats S49, S50, S53 (all units) and S95
(240, 300)
S53 180U, 240U, 300U
Each unit is equipped with a low temperature switch (freez-
estat) located on the return bend of each evaporator coil.
evaporator coils.
Each freezestat is wired in series with the compressor
contactor coil(s) through the unit control box to the A55
Unit Controller.
Each freezestat is a SPST N.C. auto-reset switch which
+ +
temperature rise. To prevent coil icing, freezestats open
during compressor operation to temporarily disable the re-
melt any accumulated frost.
If the freezestats are tripping frequently due to coil icing,
unit back in operation. Make sure to eliminate conditions
which might promote evaporator ice buildup.
9-Condenser Fans B4, B5, B21 (all units), B22 (180-
300), B23, B24 (180U, 210-300S, 300U)
See SPECIFICATIONS tables at the front of this manual
condenser fans used have single-phase motors. The fan
assembly may be removed for servicing and cleaning.
10-Pressure Transducer A185 &A186 (180U, 240U &
300U)
transducer located on the common suction line. The Unit
Controller uses the input from the transducer A185, sen-
sors RT37 and RT38 (stage one) and transducer A186
superheat for each compressor. The Unit Controller uses
this information to optimize system reliability. Verify the
sensor value using the menu path:
MAIN MENU > DATA > IN/OUTPUTS > SENSORS > LO-
CAL A185 and A186 should read within +/- 10 psi of actual
suction pressure.
To Next Page
Loading...
