036-33073-001 Rev. A (0701)
4
Unitary Products Group
ELECTRICAL POWER SUPPLY AND
CONNECTIONS
Before installing the unit, make sure that the voltage and
number of phases on the unit data plate are the same as the
available power supply. A fused disconnect or circuit breaker
must be provided within the sight of anyone working on the
unit. The size of fuses or circuit breaker required is shown on
the unit data label. Fuses must be of the time delay type. The
power supply wiring is to be connected directly to the line
side of compressor contactor as shown on the connection
wiring diagram. A ground wire must be connected to the
ground lug marked GND in the electrical control box. A 7/8-
inch diameter hole is provided in the unit corner post for the
entry of the power wiring.
ROOM THERMOSTAT AND CONTROL
WIRING
Any cooling only 24-volt room thermostat can be used with
these units. It is recommended that the thermostat sub-base
should include a fan switch, so that constant fan operation
can be selected if desired. Three control wires are required
from the unit to the thermostat. It is preferred that the wires
be colored red, yellow, and green. Using these colors simpli-
fies connecting the red, yellow, and green terminals on the
thermostat to the red, yellow, and green terminals on the unit
low voltage terminal strip. Room thermostats can be ordered
as an optional accessory for delivery with the units if desired.
BLOWER PERFORMANCE
All units have blower motors that have three speeds avail-
able, except the 460 and 575-volt units. The motors have
been selected to deliver the nominal air volume against high
external static pressures when necessary. Therefore, it will be
necessary to check the air volume obtained on every installa-
tion and change the motor speed connection accordingly, if
the air volume is too high or too low. The units are factory-
wired with the medium speed winding connected.
Three methods are available to measure the air volume. The
preferred method is to measure the actual cubic feet per
minute of air being circulated, if suitable instruments for doing
this are available. Then if necessary, change the motor speed
to try to get the nominal air volume of 400 CFM per ton of
cooling capacity, within plus or minus 10 percent.
The second method is to measure the difference between the
supply and return air temperatures. The temperature differ-
ence should be in the range of 18°F to 25°F. If it is not, reduce
the motor speed if it is less than 18°F, and increase the motor
speed if it is more than 25°F .
The third method is to measure the external static pressure
obtained, and use the fan perfom1ance table for the unit. The
following performance tables are 230-volt operation. Slightly
lower air volumes will be obtained on 208-volt operation.
1.
At higher evaporator air flows and wet bulb conditions,
condensate carry-over may occur. Adjust airflow down-
ward as necessary.
2.
Values include pressure drop from wet coil and clean fil-
ters.
CONDENSER WATER SUPPLY AND
CONNECTIONS
The cooling water for the condenser may be from the mains,
a cooling tower, or a chilled water system. An automatic
water flow regulating valve is normally required, except if the
inlet water temperature is constant and the flow rate can be
pre-set and turned on and off by some other means, such as
a pump or solenoid valve.
Automatic water flow regulating valves are available as
accessories in either 3/8, 1/2, or 3/4-inch sizes and for maxi-
mum water pressure ratings of 150 PSI or 350 PSI. The fol-
lowing table shows the recommended valve size for each unit
model depending on the temperature of the water supply
available.
TABLE 2: EVAPORATOR BLOWER PERFORMANCE (CFM)
Unit
Model
Blower
Speed
External Static Pressure (in w.g.)
0.1
0.2
0.3
0.4
0.5
0.6
0.7
060
High
2200
2120
2040
1980
1880
1780
1660
Med.
2060
2020
1940
1880
1800
1700
1600
Low
1800
1780
1740
1680
1620
1560
-
048
High
1900
1840
1780
1720
1620
1540
1440
Med.
1720
1680
1640
1580
1520
1420
1320
Low
-
1405
1400
1380
1340
-
-
036
High
1420
1370
1310
1250
1180
1110
1020
Med.
1300
1260
1220
1170
1110
1040
960
Low
-
1120
1110
1070
1030
960
-
030
High
1240
1190
1130
1080
1010
930
850
Med.
1050
1030
1000
960
910
840
750
Low
-
9 25
910
880
830
770
-
024
High
1070
1020
970
920
850
770
690
Med.
930
910
880
840
780
710
630
Low
810
805
800
770
730
670
-
018
High
770
730
695
645
590
525
-
Med.
690
660
625
585
5 3 0
-
-
Low
520
500
495
-
-
-
-
012
High
480
455
425
400
365
325
-
Med.
425
410
380
350
315
-
-
Low
350
335
315
-
-
-
-
