Carrier 48HC D17 Series Service And Maintenance Instructions page 56

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.
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$er IV will adjust the outside air
dampers to minimum position. If the outdoor-air
temperature is below the setpoint, the position of the
outside air dampers will be controlled to provided free
cooling using outdoor air. When in this mode, the LED
next to the free cooling setpoint potentiometer will be on.
The changeover temperature setpoint is controlled by the
free cooling setpoint potentiometer located on the control.
(See Fig. 69.) The scale on the potentiometer is A, B, C,
and D. See Fig. 71 for the corresponding temperature
changeover values.
Fig. 69 - - EconoMi$er IV Controller Potentiometer
and LED Locations
19
LED ON
18
D
17
LED ON
LED OFF
16
C
15
14
LED OFF
13
12
11
10
9
40 45 50 55 60 65
DEGREES FAHRENHEIT
Fig. 70 - - Outside Air Temperature Changeover
Setpoints
C06034
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 0.25
STATIC PRESSURE (in. wg)
Fig. 71 - - 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
CRTEMPSN002A00). The accessory sensor must be
mounted in the return airstream. (See Fig. 72.) Wiring is
provided in the EconoMi$er IV wiring harness.
ECONOMI$ERIV
Fig. 72 - - 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.
69.)
Outdoor Enthalpy Changeover
For enthalpy control, accessory enthalpy sensor (part
number HH57AC078) is required. Replace the standard
outdoor dry bulb temperature sensor with the accessory
enthalpy sensor in the same mounting location. (See Fig.
73.) 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$er IV
controller. The setpoints are A, B, C, and D. (See Fig. 74.)
The factory-installed 620-ohm jumper must be in place
across terminals S and SR+ on the EconoMi$er IV
R
controller.
56
0.30 0.35 0.40 0.45 0.50
C06031
sensor (part number
ECONOMI$ERIV
CONTROLLER
GROMMET
RETURN AIR
SENSOR
RETURN DUCT
(FIELD-PROVIDED)
C07085