37
Outdoor Air Lockout Sensor
The EconoMi$er IV is equipped with an ambient temperature
lockout switch located in the outdoor airstream which is used to
lock out the compressors below a 42°F (6°C) ambient tempera-
ture. See Fig. 53 on page 33.
ECONOMI$ER IV CONTROL MODES
Determine the EconoMi$er IV control mode before set up of the
control. Some modes of operation may require different sensors.
The EconoMi$er IV accessory is supplied from the factory with
a supply-air temperature sensor and an outdoor-air temperature
sensor. This allows for operation of the EconoMi$er IV with out-
door air dry bulb changeover control. Additional accessories can
be added to allow for different types of changeover control and
operation of the EconoMi$er IV and unit.
Outdoor Dry Bulb Changeover
The standard controller is shipped from the factory configured for
outdoor dry bulb changeover control. For this control mode, the
outdoor temperature is compared to a selectable set point on the
OAT sensor. If the outdoor air temperature is above the set point,
the EconoMi$er IV will adjust the outdoor air dampers to mini-
mum position. If the outdoor air temperature is below the set
point, the position of the outdoor air dampers will be controlled to
provide free cooling using outdoor air. When in this mode, the
Free Cool LED next to the outdoor enthalpy set point (ABCD) po-
tentiometer will be on. The changeover temperature set point is
controlled by the DIP switches on the sensor. See Fig. 60 for the
switch positions corresponding to the temperature changeover val-
ues. The ABCD potentiometer on the controller should be turned
fully clockwise (CW) to the “D” position. See Fig. 61 for damper
leakage.
Fig. 60 — Outdoor Air Temperature
Changeover Set Points
Outdoor Enthalpy Changeover
For enthalpy control, accessory enthalpy sensor
(P/N: HH57AC078) is required. Replace the standard outdoor
dry bulb temperature sensor with the accessory enthalpy sensor
in the same mounting location. See Fig. 62. When the outdoor
air enthalpy rises above the outdoor enthalpy changeover set
point, the outdoor-air damper moves to its minimum position.
The outdoor enthalpy changeover set point is set with the out-
door enthalpy set point potentiometer on the EconoMi$er
®
IV
controller. The set points are A, B, C, and D. See Fig. 63 and
64. The factory-installed 620-ohm jumper must be in place
across terminals S
R
and SR+ on the EconoMi$er IV controller.
Differential Enthalpy Control
For differential enthalpy control, the EconoMi$er IV controller
uses 2 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 out-
door) for cooling. For example, when the outdoor air has a
lower enthalpy than the return air, the EconoMi$er IV opens to
bring in outdoor air for free cooling.
Replace the standard outside air dry bulb temperature sensor
with the accessory enthalpy sensor in the same mounting loca-
tion. See Fig. 53 on page 33. Mount the return air enthalpy sen-
sor in the return air duct. See Fig. 62. Wiring is provided in the
EconoMi$er IV wiring harness. See Fig. 57 on page 35. 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. See Fig. 63 and 64.
Table 12 — Supply Air Sensor
Temperature/Resistance Values
TEMPERATURE (°F) RESISTANCE (ohms)
–58 220,250
–40 100,000
–22 53,010
–4 29,091
14 16,500
32 9,795
50 5,970
68 3,747
77 3,000
86 2,416
104 1,597
122 1,080
140 746
158 525
176 376
185 321
194 274
212 203
230 153
248 116
257 102
266 89
284 70
302 55
123
ON
OFF
123
ON
OFF
123
ON
OFF
123
ON
OFF
123
ON
OFF
123
ON
OFF
123
ON
OFF
123
ON
OFF
48°F
53°F
55°F
58°F
63°F
68°F
73°F
78°F
DIP Switch
Position
Changeover
Temperature
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