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B−Cooling Components Figures 10 and 11
All units use independent cooling circuits (figures 8 and 9)
consisting of separate compressors, condenser coils and
evaporator coils. Six draw−through type condenser fans are
used in all units. All units are equipped with belt-drive blow-
ers which draw air across the evaporator during unit opera-
tion.
Cooling may be supplemented by a factory- or field-
installed economizer. The evaporators are slab type
and are stacked. Each evaporator uses a thermostatic ex-
pansion valve as the primary expansion device. Each evap-
orator 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. Additional
protection is provided by low ambient switches and freezes-
tats (on each evaporator).
1−Compressors B1, B2, B13, B20
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.
All units use 4 scroll compressors. Early model 360H units
use 3 scroll compressors. See figures 10 and 11. Compres-
sor capacity may vary from stage to stage. In all cases, the
capacity of each compressor is added to reach the total ca-
pacity of the unit. Compressor electrical specifications can
be found in the SPECIFICATIONS section in this manual.
Each compressor is energized by a corresponding com-
pressor contactor.
NOTE−Refer to the wiring diagram section for specific unit
operation.
2−Crankcase Heaters HR1, HR2, HR5, HR11
All units use belly-band type crankcase heaters. Heater
HR1 is installed around compressor B1, heater HR2 com-
pressor B2, HR5 compressor B13, and HR11 compressor
B20. Crankcase heater wattage varies by compressor
size.
IMPORTANT
Pressure switch settings are significant higher on
R410A charged units than R22 charged units.
3−High Pressure Switches S4, S7, S28, S96
The high pressure switch 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.
S4 (first circuit), S7 (second circuit), S28 (third circuit), and S96
(fourth circuit) are wired in series with the respective compres-
sor contactor coils.
Main control A55 has a three−strike counter before lock-
ing out the particular compressor circuit. This means the
control allows three high pressure trips per one thermo-
stat demand. The control can be reset by breaking and
remaking the thermostat demand or manually resetting
the control.
Units charged with R22
When discharge pressure rises to 450 +
10 psig (3103 +
69 kPa) (indicating a problem in the system) the switch
opens and the respective compressor is de−energized
(the economizer can continue to operate). When dis-
charge pressure drops to 310 +
20 psig (2137 + 138 kPa)
the pressure switch will close.
Units charged with R410A
When discharge pressure rises to 650 ± 10 psig (4413 ±
69 kPa) (indicating a problem in the system) the switch
opens and the respective compressor is de−energized
(the economizer can continue to operate). When dis-
charge pressure drops to 475 ± 20 psig (3275 ± 138 kPa)
the pressure switch will close.
4−Low Ambient Switches S11, S84, S85, S94
The low ambient switch is an auto-reset SPST N.O. pres-
sure switch which allows for mechanical cooling opera-
tion at low outdoor temperatures. All units are equipped
with this switch. In all models a switch is located in each
liquid line prior to the indoor coil section.
In the 360H units with 3 compressors S11 (compressor one),
S84 (compressor two), and S85 (compressor three) are wired
in parallel, wired to the low ambient switch relay K159. In all
other 248H, 300H and 360H units S11 and S84 are in paral-
lel, wired to outdoor fan relay K10, while S85 and S94 (com-
pressor four) are in parallel, wired to third outdoor fan relay
K149.
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