Bryant Preferred 549K 04-06 Service And Maintenance Instructions page 33

Table 12 — Supply Air Sensor Temperature/Resistance
TEMPERATURE (F)
-58
-40
-22
-4
14
32
50
68
77
86
104
122
140
158
176
185
194
212
230
248
257
266
284
302
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 minimum position. If the outdoor air tempera-
ture is below the set point, the position of the outdoor air
dampers will be controlled to provide free cooling using out-
door air. When in this mode, the Free Cool LED next to the
outdoor enthalpy set point (ABCD) potentiometer will be on.
The changeover temperature set point is controlled by the dip
switches on the sensor. See Fig. 58 for the switch positions cor-
responding to the temperature changeover values. The ABCD
potentiometer on the controller should be turned fully clock-
wise (CW) to the "D" position. See Fig. 59 for damper leakage.
Outdoor Enthalpy Changeover
For enthalpy control,
(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. 60. When the outdoor
air enthalpy rises above the outdoor enthalpy changeover set
Values
RESISTANCE (ohms)
220,250
100,000
53,010
29,091
16,500
9,795
5,970
3,747
3,000
2,416
1,597
1,080
746
525
376
321
274
203
153
116
102
89
70
55
accessory enthalpy
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$er
controller. The set points are A, B, C, and D. See Fig. 61 and
62. The factory-installed 620-ohm jumper must be in place
across terminals S
Differential Enthalpy Control
For differential enthalpy control, the EconoMi$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 out-
door) for cooling. For example, when the outdoor air has a
lower enthalpy than the return air, the EconoMi$er IV opens to
bring in outdoor air for free cooling.
Replace the standard outside air dry bulb temperature sensor
with the accessory enthalpy sensor in the same mounting loca-
tion. See Fig. 51 on page 29. Mount the return air enthalpy sen-
sor in the return air duct. See Fig. 60. Wiring is provided in the
EconoMi$er IV wiring harness. See Fig. 55 on page 31. The
outdoor enthalpy changeover set point is set with the outdoor
enthalpy set point potentiometer on the EconoMi$er IV control-
ler. When using this mode of changeover control, turn the en-
thalpy set point potentiometer fully clockwise to the D setting.
See Fig. 61 and 62.
DIP SWITCH
POSITION
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
sensor
Fig. 58 — Outdoor Air Temperature
33
and SR+ on the EconoMi$er IV controller.
R
CHANGEOVER
TEMPERATURE
48°F
1 2 3
53°F
1 2 3
55°F
1 2 3
58°F
1 2 3
63°F
1 2 3
68°F
1 2 3
73°F
1 2 3
78°F
1 2 3
Changeover Set Points
IV
®