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2-Freezestat S49
Each unit is equipped with a low temperature switch
(freezestat) located on a return bend of each evaporator
coil.
The freezestat is wired in series with the compressor con
tactor K1. The 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 tempo
rarily 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 evap
orator ice buildup.
3-High Pressure Switch S4
The high pressure switch is an auto reset SPST N.C. switch
which opens on a pressure rise.
S4 is located in the compressor discharge line and wired in se
ries with the compressor contactor coil.
When discharge pressure rises to 640 ± 20 psig (4412 ±
138 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 ± 30 psig (3275 ± 206 kPa),
the switch closes.
4-Low Ambient Switches S11 (optional)
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. In all models the
switch is located in each liquid line prior to the indoor coil
section and is wired in series with outdoor fan B4. When
S11 opens B4 is de-energized.
In G, J and M voltage units, S11 is wired in series with out
door fan relay K10 coil and when opened breaks 24 volts to
the coil, de-energizing outdoor fan B4.
When liquid pressure rises to 450 ± 10 psig (3102 ± 69
kPa), the switch closes and the condenser fan is ener
gized. When discharge pressure in drops to 240 ± 10 psig
(1655 ± 69 kPa), the switch opens and the condenser fan is
de-energized. This intermittent fan operation results in
higher evaporating temperature allowing the system to op
erate without icing the evaporator coil and losing capacity.
5-Low Temperature Switch S3 (optional)
(compressor monitor)
S3 is a SPST bimetal thermostat which opens on tempera
ture drop. It is wired in line with the 24VAC compressor con
tactor. When outdoor temperature drops below 40° F (4.5°
C) the switch opens and de-energizes the compressor.
When the compressor is de-energized the cooling demand
is handled by the economizer. The switch automatically re
sets when outdoor temperature rises to 50° F (10° C).
C-Blower Compartment
1-Blower Wheels
All belt drive units use 10” x 10” (254 mm x 254 mm) blower
wheels. The KGB024, 030, 036 and 048 direct drive units use
10” x 10” (254 mm x 254 mm) blower wheels also. The
KCB060 direct drive units use 11” x 10” (279 mm x 254 mm)
blower wheels. KG072/074 units use a 15” x 9” (381 mm x 228
mm) blower wheel.
2-Indoor Blower Motor Capacitor C4
All single phase blower motors are PSC and requires a run
capacitor. Ratings may vary from each motor. See motor
nameplate for capacitor ratings.
3-Indoor Blower Motor B3
All direct drive units use single phase PSC motors. Belt
drive units use single or three phase motors (same as sup
ply voltage). CFM adjustments on belt drive units are made
by adjusting the motor pulley (sheave). CFM adjustments
on direct drive units are made by changing speed taps. Mo
tors are equipped with sealed ball bearings. All motor speci
fications are listed in the SPECIFICATIONS (table of con
tents) in the front of this manual. Units may be equipped
with motors manufactured by various manufacturers,
therefore electrical FLA and LRA specifications will vary.
See unit rating plate for information specific to your unit.
IMPORTANT
Three phase scroll compressors must be phased se
quentially for correct compressor and blower rota
tion. Follow “COOLING START-UP” section of instal
lation instructions to ensure proper compressor and
blower operation.
A-Blower Operation
Initiate blower demand at thermostat according to instructions
provided with thermostat. Unit will cycle on thermostat de
mand. The following steps apply to applications using a typi
cal electro-mechanical thermostat.
1- Blower operation is manually set at the thermostat sub
base fan switch. With fan switch in ON position, blow
ers will operate continuously.
2- With fan switch in AUTO position, the blowers will cycle
with demand. Blowers and entire unit will be off when
system switch is in OFF position.
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