17
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 2.) The EconoMi$er IV assembly is supplied from the
factory with a supply air temperature sensor, a low temperature
compressor lockout switch, and an outdoor air temperature sensor.
This allows for operation of the EconoMi$er IV assembly 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$er IV controller and unit.
OUTDOOR DRY BULB CHANGEOVER
The standard controller is shipped from the factory configured for
outdoor dry bulb changeover control. The outdoor air and supply
air temperature sensors are included as standard. For this control
mode, the outdoor temperature is compared to a selectable set
point sensor. (See Fig. 39.) If the outdoor-air temperature is above
the set point, the EconoMi$er IV controller will adjust the outdoor
air damper 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 be on. The changeover temperature set point is selected by the
switches on the sensor. See Fig. 39 for the corresponding
temperature changeover values.
OUTDOOR ENTHALPY CHANGEOVER
For enthalpy control, accessory enthalpy sensor (part number
CRENTDIF004A00 for Carrier and Bryant, AXB078ENT for
ICP) is required. Replace the standard outdoor dry bulb
temperature sensor with the accessory enthalpy sensor in the same
mounting location. (See Fig. 38.) 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 out-
door enthalpy set point potentiometer on the EconoMi$er IV
controller. The set points are A, B, C and D. (See Fig. 40.) The
factory-installed 620-ohm jumper must be in place across
terminals SR and SR+ on the EconoMi$er IV controller. (See
Fig. 15.)
DIFFERENTIAL ENTHALPY CONTROL
For differential enthalpy control, the EconoMi$er IV controller
(see Fig. 41) uses two enthalpy sensors (AXB078ENT and
CRENTDIF004A00), one in the outside air and one in the return
airstream. The EconoMi$er IV controller compares the outdoor
air enthalpy to the return air enthalpy to determine EconoMi$er IV
controller use. The controller selects the lower enthalpy air (return
or outdoor) for cooling. For example, when the outdoor air has a
lower enthalpy than the return air and is below the set point, the
EconoMi$er IV damper opens to bring in outdoor air for free
cooling.
Replace the standard outside air dry bulb temperature sensor
with the accessory enthalpy sensor in the same mounting
location. (See Fig. 38.) Mount the return air enthalpy sensor in
the return air duct. (See Fig. 42.) When using this mode of
changeover control, turn the enthalpy set point potentiometer
fully clockwise to the D setting.
Fig. 39 — Selectable Temperature Options
ON
OFF
1
2 3
1
2 3
1
2 3
1
2 3
1
2 3
1
2 3
1
2 3
1
2 3
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
DIP SWITCH
POSITION
CHANGEOVER
TEMPERATURE
48°F
53°F
55°F
58°F
63°F
68°F
73°F
78°F
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