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DIFFERENTIAL ENTHALPY CONTROL
For differential enthalpy control, the EconoMi$er IV controller
uses two enthalpy sensors (HH57AC078 and CRENT-
DIF004A00), one in the outside air and one in the return air duct.
The EconoMi$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 sensor with
the accessory enthalpy sensor in the same mounting location. See
Fig. 75. Mount the return air enthalpy sensor in the return air duct.
See Fig. 74. Wiring is provided in the EconoMi$er IV wiring har-
ness. See Fig. 67. The outdoor enthalpy changeover set point is set
with the outdoor enthalpy set point potentiometer on the
EconoMi$er IV controller. When using this mode of changeover
control, turn the enthalpy set point potentiometer fully clockwise
to the D setting.
CONTROL
CONTROL POINT
CURVE
APPROX. deg. F (deg. C)
AT 50% RH
A
73 (23)
B
70 (21)
C
67 (19)
D
63 (17)
65
(18)
60
(16)
A
55
(13)
B
50
C
(10)
45
D
(7)
40
(4)
35
(2)
35
40
45
50
55
60
(2)
(4)
(7)
(10)
(13)
(16)
APPROXIMATE DRY BULB TEMPERATURE--degrees F (degrees C)
Fig. 76 — Enthalpy Changeover Set Points
INDOOR AIR QUALITY (IAQ) SENSOR INPUT
The IAQ input can be used for demand controlled ventilation con-
trol based on the level of CO
duct.
Mount the accessory IAQ sensor according to manufacturer speci-
fications. The IAQ sensor should be wired to the AQ and AQ1 ter-
minals of the controller. Adjust the DCV potentiometers to corre-
spond to the DCV voltage output of the indoor air quality sensor at
the user-determined set point. See Fig. 77.
85
90
95
100
105
110
(29)
(32)
(35)
(38)
(41)
(43)
80
(27)
75
(24)
70
(21)
A
B
C
D
65
70
75
80
85
90
95
100
105
110
(18)
(21)
(24)
(27)
(29)
(32)
(35)
(38)
(41)
(43)
measured in the space or return air
2
6000
5000
4000
3000
2000
1000
0
2
DAMPER VOLTAGE FOR MAX VENTILATION RATE
Fig. 77 — CO
If a separate field-supplied transformer is used to power the IAQ
sensor, the sensor must not be grounded or the EconoMi$er IV
control board will be damaged.
When using demand ventilation, the minimum damper position
represents the minimum ventilation position for VOC (volatile or-
ganic compounds) ventilation requirements. The maximum de-
mand ventilation position is used for fully occupied ventilation.
When demand ventilation control is not being used, the minimum
position potentiometer should be used to set the occupied ventila-
tion position. The maximum demand ventilation position should
be turned fully clockwise.
EXHAUST SET POINT ADJUSTMENT
The exhaust set point will determine when the exhaust fan runs
based on damper position (if accessory power exhaust is in-
stalled). The set point is modified with the Exhaust Fan set point
(EXH SET) potentiometer. See Fig. 71. The set point represents
the damper position above which the exhaust fans will be turned
on. When there is a call for exhaust, the EconoMi$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.
HIGH LIMIT
CURVE
MINIMUM POSITION CONTROL
There is a minimum damper position potentiometer on the
EconoMi$er IV controller. See Fig. 71. The minimum damper po-
sition maintains the minimum airflow into the building during the
occupied period.
When using demand ventilation, the minimum damper position
represents the minimum ventilation position for Volatile Organic
Compound (VOC) ventilation requirements. The maximum de-
mand ventilation position is used for fully occupied ventilation.
When demand ventilation control is not being used, the minimum
position potentiometer should be used to set the occupied ventila-
tion position. The maximum demand ventilation position should
be turned fully clockwise.
Adjust the minimum position potentiometer to allow the mini-
mum 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 outdoor and return-air
temperatures.
51
CO SENSOR MAX RANGE SETTING
2
3
4
5
6
Sensor Maximum Range Settings
2
800 ppm
900 ppm
1000 ppm
1100 ppm
7
8
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