Dc b a – Carrier 50TFQ008-012 User Manual

Page 22

Differential Dry Bulb Control — For differential dry bulb
control the standard outdoor dry bulb sensor is used in conjunc-
tion with an additional accessory dry bulb sensor (part number
CRTEMPSN002A00). The accessory sensor must be mounted
in the return airstream. See Fig. 34. Wiring is provided in the
EconoMi$er IV wiring harness. See Fig. 26.

In this mode of operation, the outdoor-air temperature is

compared to the return-air temperature and the lower tempera-
ture airstream is used for cooling. When using this mode of
changeover control, turn the enthalpy set point potentiometer
fully clockwise to the D setting. See Fig. 32.
Outdoor Enthalpy Changeover — For enthalpy control, ac-
cessory enthalpy sensor (part number HH57AC078) is re-
quired. Replace the standard outdoor dry bulb temperature sen-
sor with the accessory enthalpy sensor in the same mounting
location. See Fig. 19. When the outdoor air enthalpy rises
above the outdoor enthalpy changeover set point, the outdoor-
air damper moves to its minimum position. The outdoor
enthalpy changeover set point is set with the outdoor enthalpy
set point potentiometer on the EconoMi$er IV controller. The
set points are A, B, C, and D. See Fig. 35. The factory-installed
620-ohm jumper must be in place across terminals SR and SR+
on the EconoMi$er IV controller. See Fig. 19 and 36.

Differential Enthalpy Control — For differential enthalpy
control, the EconoMi$er IV controller uses two enthalpy sen-
sors (HH57AC078 and CRENTDIF004A00), one in the out-
side air and one in the return air duct. The EconoMi$er IV
controller compares the outdoor air enthalpy to the return air
enthalpy to determine EconoMi$er IV use. The controller
selects the lower enthalpy air (return or outdoor) for cooling.
For example, when the outdoor air has a lower enthalpy than
the return air, the EconoMi$er IV opens to bring in outdoor air
for free cooling.

Replace the standard outside air dry bulb temperature sen-

sor with the accessory enthalpy sensor in the same mounting
location. See Fig. 19. Mount the return air enthalpy sensor in
the return air duct. See Fig. 34. Wiring is provided in the
EconoMi$er IV wiring harness. See Fig. 26. The outdoor en-
thalpy changeover set point is set with the outdoor enthalpy set
point potentiometer on the EconoMi$er IV controller. When
using this mode of changeover control, turn the enthalpy set-
point potentiometer fully clockwise to the D setting.
Indoor Air Quality (IAQ) Sensor Input — The IAQ input
can be used for demand control ventilation control based on the
level of CO

measured in the space or return air duct.

Mount the accessory IAQ sensor according to manufacturer

specifications. The IAQ sensor should be wired to the AQ and
AQ1 terminals of the controller. Adjust the DCV potentiome-
ters to correspond to the DCV voltage output of the indoor air
quality sensor at the user-determined set point. See Fig. 37.

If a separate field-supplied transformer is used to power the

IAQ sensor, the sensor must not be grounded or the
EconoMi$er IV control board will be damaged.

Fig. 32 — EconoMi$er IV Controller Potentiometer

and LED Locations

LED ON

LED OFF

100

DEGREES FAHRENHEIT

Fig. 33 — Outside Air Temperature

Changeover Set Points

ECONOMI$ER IV

ECONOMI$ER IV
CONTROLLER

GROMMET

RETURN AIR
SENSOR

RETURN DUCT
(FIELD-PROVIDED)

Fig. 34 — Return Air Temperature or Enthalpy

Sensor Mounting Location