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6-Defrost Pressure Switch S104
The defrost pressure switch S104 is an auto‐reset SPST
N.C. pressure switch which opens on a pressure rise. The
switch is located on the discharge line and is wired in series
with the CMC1 control board.
When discharge pressure reaches 450 + 10 psig (3102
$
69 kPa) in either circuit (indicating defrost is completed) the
appropriate switch opens. The switches automatically re
set when pressure in the suction line drops to 300 + 20 psig
(2068
$
138 kPa).
7-Defrost Temperature Switch S6 and S9
Defrost thermostat switches S6 and S9 have S.P.S.T. N.O.
contacts which close on a temperature fall (initiating de
frost). The switches are located on the expansion valve
distributor assembly at the inlet to the outdoor coil. The
switch monitors the outdoor coil suction temperature to
determine when defrost is needed. When the outdoor coil
suction temperature falls to 35
°
F + 4
°
F (1.7
°
C + 2.2
°
C) the
switch closes (initiating defrost after minimum run time of
30, 60, or 90 minutes). When the temperature rises to 60
°
F
+ 5
°
F (15.6
°
C + 2.8
°
C) the switch opens.
8-Filter Drier (all units)
Units have a filter drier located in the liquid line of each re
frigerant circuit at the exit of each outdoor coil. The drier re
moves contaminants and moisture from the system.
9-Condenser Fan Motors B4 and B5
See specifications section of this manual for specifications
of condenser fans B4 and B5. All motors are ball bearing
type single-phase motors. The fans may be removed for
servicing and cleaning by removing the fan grilles.
C-Blower Compartment
NOTE -
Units equipped a Variable Frequency Drive (VFD)
are designed to operate on balanced, three-phase power.
Operating units on unbalanced three-phase power will re
duce the reliability of all electrical components in the unit.
Unbalanced power is a result of the power delivery system
supplied by the local utility company. Factory-installed in
verters are sized to drive blower motors with an equivalent
current rating using balanced three-phase power. If unbal
anced three-phase power is supplied; the installer must re
place the existing factory-installed inverter with an inverter
that has a higher current rating to allow for the imbalance.
Refer to the installation instructions for additional informa
tion and available replacements
.
All units are equipped with belt drive blowers.
1-Blower Wheels
All units have one 15 in. x 15 in. (381 mm x 381 mm) blower
wheel.
2-Indoor Blower Motor B3
All units use three‐phase single‐speed blower motors.
CFM adjustments are made by adjusting the motor pulley
(sheave). Motors are equipped with sealed ball bearings.
All motor specifications are listed in the SPECIFI
CATIONS(table of contents) in the front of this manual.
Units may be equipped with motors manufactured by vari
ous manufacturers, therefore electrical FLA and LRA spec
ifications will vary. See unit rating plate for information spe
cific to your unit.
OPERATION / ADJUSTMENT
Blower Operation
Initiate blower demand at thermostat according to instruc
tions provided with thermostat. Unit will cycle on thermostat
demand. The following steps apply to applications using a
typical 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.
Determining Unit CFM
1- The following measurements must be made with a dry
indoor coil. Run blower
without
a cooling demand.
Measure the indoor blower shaft RPM. Air filters must
be in place when measurements are taken.
Units equipped with VFD
-
Initiate high speed blower without cooling demand. Discon
nect high pressure switches S4 and S7. Run the blower
with Y1 and Y2 demands.
2- With all access panels in place, measure static pres
sure external to unit (from supply to return)
.
Blower per
formance data is based on static pressure readings
taken in locations shown in figure 9.
Note - Static pressure readings can vary if not taken where
shown.
3- Refer to blower tables in BLOWER DATA (table of con
tents) in the front of this manual. Use static pressure and
RPM readings to determine unit air volume.
4- The blower RPM can be adjusted at the motor pulley.
Loosen Allen screw and turn adjustable pulley clock
wise to increase CFM. Turn counterclockwise to de
crease CFM. See figure 8. Do not exceed minimum and
maximum number of pulley turns as shown in table 2.
TABLE 2
MINIMUM AND MAXIMUM PULLEY ADJUSTMENT
Belt
Minimum
Turns Open
Maximum
Turns Open
A Section
No minimum
5
B Section
1*
6
*No minimum number of turns open when B belt is used on
pulleys 6” O.D. or larger.