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36
Supply Air Temperature (SAT) Sensor
The supply air temperature sensor is a 3 K thermistor located at
the inlet of the indoor fan. (See Fig. 39.) This sensor is factory
installed. The operating range of temperature measurement is 0
to 158_F. See Table 6 for sensor temperature/resistance values.
Table 6 —Supply Air Sensor Temperature/
Resistance Values
TEMPERATURE (F) RESISTANCE (ohms)
–58
200,250
–40
100,680
–22
53,010
–4
29,091
14
16,590
32
9,795
50
5,970
68
3,747
77
3,000
86
2,416
104
1,597
122
1,080
140
746
158
525
176
376
185
321
194
274
212
203
230
153
248
116
257
102
266
89
284
70
302
55
17 1/4”
DIVIDER
BAROMETRIC
RELIEF
CLEANABLE
ALUMINUM
FILTER
FILTER
HOOD
FILTE
R
CLIP
OUTSIDE
AIR
C06027
Fig. 33 --- Filter Installation
The temperature sensor looks like an eyelet terminal with wires
running to it. The sensor is located in the “crimp end” and is
sealed from m oisture.
Outdoor Air Lockout Sensor
The Economi$er IV is equipped with an ambient temperature
lockout switch located in the outdoor air stream which is used to
lockout the compressors below a 42_F ambient temperature. (See
Fig. 27.)
Economi$er IV Control
Modes
IMPORTANT: The optional EconoMi $er2 does not inc l ude a
controll er. The EconoMi$e r 2 is operated by a 4 to 20 mA
signal
from an existing f ield-supplied controller ( such as PremierLink
control) . See Fig. 35 for wir ing informa tion.
Determine the EconoMi$er IV control mode before set up of the
control. Some modes of operation may require different
sensors. Refer to Table 7. The EconoMi$er IV is supplied from
the factory with a supply--air temperature sensor and an outdoor--
air temperature sensor. This allows for operation of the
EconoMi$er IV with outdoor air dry bulb changeover control.
Additional accessories can be added to allow for different types of
changeover control and operation of the EconoMi$er IV and unit.
Table7—Economi$erIVSensorUsage
APPLICATION
ECONOMI$ER IV WITH OUTDOOR AIR
DRY BULB SENSOR
Accessories Required
Outdoor Air
Dry Bulb
None. The outdoor air dry bulb sensor
isfactory installed.
Differential
Dry Bulb
CRTEMPSN002A00*
Single Enthalpy HH57AC078
Differential
Enthalpy
HH57AC078
and
CRENTD IF004A00*
CO
2
for DCV
Control using a
Wall-Mounted
CO
2
Sensor
33ZCSENCO2
CO
2
for DCV
Control using a
Duct-Mounted
CO
2
Sensor
33ZCSENCO2†
and
33ZCASPCO2**
O
R
CRCBDIOX005A00††
*CRENTDIF004A00 and CRTEMPSN002A00 accessories are used on many
different base units. Assuch, these kits may contain parts that will not be
needed for in stallation.
† 33ZCSENCO2 is an accessory CO
2
sensor.
** 33ZCASPCO2 isan accessory aspirator box required for duct-mounted
applications.
†† CRCBDIOX005A00 is an accessory that contains both 33ZC S ENCO2
and 33ZCASPCO2 accessories.
Outdoor Dry Bulb Changeover
The standard controller is shipped from the factory configured for
outdoor dry bulb changeover control. The outdoor--air and
supply--air temperature sensors are included as standard. For this
control mode, the outdoor temperature is compared to an
adjustable set point selected on the control. If the outdoor-air
temperature is above the set point, the EconoMi$er IV will adjust
the outdoor-air dampers to minimum position. If the outdoor air
temperature is below the set point, the position of the outdoor air
dampers will be controlled to provide free cooling using outdoor
air. When in this mode, the LED next to the free cooling set point
potentiometer will beon. The changeover temperature set point is
controlled by the free cooling set point potentiometer located on
the control. (See Fig. 40.) The scale on the potentiometer is A, B,
C, an d D. See Fig. 41 for the corresponding temperature
changeover values.
Differential Dry Bulb Control
For differential dry bulb control the standard outdoor dry bulb
sensor is used in conjunction with an additional accessory dry
bulb sensor (part number CRTEMPSN002A00). The accessory
sensor must be mounted in the return airstream. (See Fig. 42.)
Wiring is provided in the EconoMi$er IV wiring harness. (See
Fig. 33.)
In this mode of operation, the outdoor-air temperature is
compared to the r eturn-air temperature and the lower temperature
airstream is used for cooling. When using this mode of
changeover control, turn the enthalpy setpoint potentiometer fully
clockwise to the D setting. (See Fig. 40.)
50HE,HJ