Carrier 48TC series, Service And Maintenance Instructions, Page: 51 / 112

51
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. 67.) This sensor is factory in -
stalled. The operating range of temperature measurement is 0°F to
158°F (–18°C to 70°C).
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 moisture.
Fig. 67 — Supply Air Sensor Location
Fig. 68 — Outside Air Temperature Changeover
Setpoints
OUTDOOR AIR LOCKOUT SENSOR
The EconoMi$er IV is equipped with an ambient temperature
lockout switch located in the outdoor airstream which is used to
lock out the compressors below a 42°F (6°C) ambient tempera -
ture. (See Fig. 59.)
ECONOMI$ER IV CONTROL MODES
Determine the EconoMi$er IV control mode before set up of the
control. Some modes of operation may require different sensors.
(See Table 21.) The EconoMi$er IV is supplied from the factory
with a supply-air temperature sensor and an outdoor-air tempera -
ture 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.
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 setpoint, the EconoMi$er IV will adjust the outside air
dampers to minimum position. If the outdoor-air temperature is
below the setpoint, the position of the outside air dampers will be
controlled to provided free cooling using outdoor air. When in this
mode, the LED next to the free cooling setpoint potentiometer will
be on. The changeover temperature setpoint is controlled by the
free cooling setpoint potentiometer located on the control. (See
Fig. 69.) The scale on the potentiometer is A, B, C, and D. See
Fig. 70 for the corresponding temperature changeover values.
Fig. 69 — EconoMi$er IV Controller Potentiometer
and LED Locations
Fig. 70 — Outdoor-Air Damper Leakage
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. 71.) Wiring is
provided in the EconoMi$er IV wiring harness.
In this mode of operation, the outdoor-air temperature is compared
to the return-air temperature and the lower temperature airstream
is used for cooling. When using this mode of changeover control,
IMPORTANT: The optional EconoMi$er IV does not include a
controller. The EconoMi$er IV is operated by a 4 to 20 mA sig -
nal from an existing field-supplied controller. See Fig. 61 for
wiring information.
SUPPLY
AIR TEMPERATURE
SENSOR MOUNTING
LOCATION
SUPPLY AIR
TEMPERATURE
SENSOR
(SEALED
INSIDE CRIMP
END)
LED ON
LED ON
LED ON
LED ON
LED OFF
19
18
LED OFF
LED OFF
LED OFF
17
16
15
14
13
12
11
10
9
40 45 50 55 60 65 70 75 80 85 90 95
100
DEGREES FAHRENHEIT
mA
D
C
B
A
0
5
10
15
20
25
30
0.13 0.20 0.22 0.25 0.30 0.35 0.40 0.45 0.50
STATIC PRESSURE (in. wg)
FLOW
IN
CUBIC
FEET
PER
MINUTE
(cfm)