—
19
—
Outdoor Enthalpy Changeover
For enthalpy control, accessory enthalpy sensor (part num-
ber HH57AC078) is required. Replace the standard outdoor
dry bulb temperature sensor with the accessory enthalpy
sensor in the same mounting location. See Fig. 21. 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 potentiome-
ter 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. 21 and 36.
Differential Enthalpy Control
For differential enthalpy control, the EconoMi$er IV control-
ler uses two enthalpy sensors (HH57AC078 and
CRENTDIF004A00), one in the outside air and one in the
return air duct. The EconoMi$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. 21. Mount the return air enthalpy sensor
in the return air duct. See Fig. 34. Wiring is provided in the
EconoMi$er IV wiring harness. See Fig. 27. The outdoor
enthalpy changeover set point is set with the outdoor
enthalpy set point potentiometer on the EconoMi$er IV con-
troller. 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
2
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$er IV control board will be damaged.
Exhaust Set Point Adjustment
The exhaust set point will determine when the exhaust fan
runs based on damper position (if accessory power exhaust is
installed). The set point is modified with the Exhaust Fan
Set Point (EXH SET) potentiometer. See Fig. 32. The set
point represents the damper position above which the
exhaust fans will be turned on. When there is a call for
exhaust, the EconoMi$er IV controller provides a 45 ± 15
second delay before exhaust fan activation to allow the
dampers to open. This delay allows the damper to reach the
appropriate position to avoid unnecessary fan overload.
Minimum Position Control
There is a minimum damper position potentiometer on the
EconoMi$er IV controller. See Fig. 32. The minimum damper
position maintains the minimum airflow into the building
during the occupied period.
When using demand ventilation, the minimum damper posi-
tion represents the minimum ventilation position for VOC
(volatile organic compound) ventilation requirements. The
maximum demand ventilation position is used for fully occu-
pied ventilation.
When demand ventilation control is not being used, the min-
imum position potentiometer should be used to set the occu-
pied ventilation position. The maximum demand ventilation
position should be turned fully clockwise.
Adjust the minimum position potentiometer to allow the
minimum amount of outdoor air, as required by local codes,
to enter the building. Make minimum position adjustments
with at least 10 F temperature difference between the out-
door and return-air temperatures.
To determine the minimum position setting, perform the fol-
lowing procedure:
1. Calculate the appropriate mixed air temperature
using the following formula:
T
O
= Outdoor-Air Temperature
OA = Percent of Outdoor Air
T
R
= Return-Air Temperature
RA = Percent of Return Air
T
M
= Mixed-Air Temperature
As an example, if local codes require 10% outdoor air dur-
ing occupied conditions, outdoor-air temperature is 60 F,
and return-air temperature is 75 F.
(60 x .10) + (75 x .90) = 73.5 F
2. Disconnect the supply air sensor from terminals T
and T1.
3. Ensure that the factory-installed jumper is in place
across terminals P and P1. If remote damper posi-
tioning is being used, make sure that the terminals
are wired according to Fig. 27 and that the minimum
position potentiometer is turned fully clockwise.
4. Connect 24 vac across terminals TR and TR1.
5. Carefully adjust the minimum position potentiometer
until the measured mixed air temperature matches
the calculated value.
6. Reconnect the supply air sensor to terminals T and T1.
Remote control of the EconoMi$er IV damper is desirable when
requiring additional temporary ventilation. If a field-supplied
remote potentiometer (Honeywell part number S963B1128) is
wired to the EconoMi$er IV controller, the minimum position of
the damper can be controlled from a remote location.
(T
O
x
OA
) + (T
R
x
RA
) = T
M
100
100
ECONOMI$ER IV
ECONOMI$ER IV
CONTROLLER
GROMMET
RETURN AIR
SENSOR
RETURN DUCT
(FIELD-PROVIDED)
Fig. 34 — Return Air Temperature or Enthalpy
Sensor Mounting Location
Summary of Contents for DURAPAC PLUS 581B
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