Carrier 50TC*17 Series Service And Maintenance Instructions page 43

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 setpoint selected
on the control. If the outdoor-air temperature is above the
setpoint, the EconoMi$er IV will adjust the outside air
dampers to minimum position. If the outdoor-air
temperature is below the setpoint, the position of the
outside air dampers will be controlled to provided free
cooling using outdoor air. When in this mode, the LED
next to the free cooling setpoint potentiometer will be on.
The changeover temperature setpoint is controlled by the
free cooling setpoint potentiometer located on the control.
See Fig. 50. The scale on the potentiometer is A, B, C,
and D. See Fig. 51 for the corresponding temperature
changeover values.
Fig. 50 − EconoMi$er IV Controller Potentiometer
and LED Locations
19
LED ON
18
D
17
LED ON
LED OFF
16
15
14
LED OFF
13
12
11
10
9
40 45 50 55 60 65
DEGREES FAHRENHEIT
Fig. 51 − Outside Air Temperature Changeover
Setpoints
C06034
C
LED ON
B
LED ON
LED OFF
A
LED OFF
100
70 75 80 85 90 95
C06035
30
25
20
15
10
5
0
0.13 0.20 0.22
STATIC PRESSURE (in. wg)
Fig. 52 − 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 (p/n: CRTEMPSN002A00). The
accessory sensor must be mounted in the return airstream.
See Fig. 53. Wiring is provided in the EconoMi$er IV
wiring harness.
ECONOMI$ER IV
Fig. 53 − Return Air Temperature or Enthalpy Sensor
Mounting Location
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, turn the enthalpy setpoint
potentiometer fully clockwise to the D setting. See Fig. 50.
Outdoor Enthalpy Changeover
For enthalpy control, accessory enthalpy sensor (p/n:
HH57AC078) is required. Replace the standard outdoor
dry bulb temperature sensor with the accessory enthalpy
sensor in the same mounting location. See Fig. 70. When
the outdoor air enthalpy rises above the outdoor enthalpy
changeover setpoint, the outdoor-air damper moves to its
minimum position. The outdoor enthalpy changeover
setpoint is set with the outdoor enthalpy setpoint
potentiometer on the EconoMi$er IV controller. The
setpoints are A, B, C, and D. See Fig. 51. The
factory- installed 620-ohm jumper must be in place across
terminals S and SR+ on the EconoMi$er IV controller.
R
43
0.25 0.30 0.35 0.40 0.45 0.50
ECONOMI$ER IV
CONTROLLER
GROMMET
RETURN AIR
SENSOR
RETURN DUCT
(FIELD-PROVIDED)
C06031
C07085