Carrier 50FCQ 04-07 Series Service And Maintenance Instructions page 39

Table 12 — Supply Air Sensor
Temperature/Resistance Values
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$er IV accessory is supplied from the factory with a
supply-air temperature sensor and an outdoor-air temperature sen-
sor. This allows for operation of the EconoMi$er IV with outdoor
air dry bulb changeover control. Additional accessories can be
added to allow for different types of changeover control and oper-
ation 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. 63 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. 64 for damper
leakage.
Outdoor Enthalpy Changeover
For enthalpy control,
(P/N: HH57AC078) is required. Replace the standard outdoor dry
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 sensor
bulb temperature sensor with the accessory enthalpy sensor in the
same mounting location. See Fig. 65. When the outdoor air enthal-
py rises above the outdoor enthalpy changeover set point, the out-
door-air damper moves to its minimum position. The outdoor
enthalpy changeover set point is set with the outdoor enthalpy set
point potentiometer on the EconoMi$er
points are A, B, C, and D. See Fig. 66 and 67. The factory-
installed 620-ohm jumper must be in place across terminals S
and SR+ on the EconoMi$er IV controller.
DIP Switch
Position
ON
OFF
1 2 3
ON
OFF
1 2 3
ON
OFF
1 2 3
ON
OFF
1 2 3
ON
OFF
1 2 3
ON
OFF
1 2 3
ON
OFF
1 2 3
ON
OFF
1 2 3
Fig. 63 — Outdoor Air Temperature
Changeover Set Points
Differential Enthalpy Control
For differential enthalpy control, the EconoMi$er IV controller
uses 2 enthalpy sensors (P/N: HH57AC078 and CRENT-
DIF004A00), one in the outside air and one in the return air duct.
The EconoMi$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. 56 on page 35. Mount the return air enthalpy sensor in the re-
turn air duct. See Fig. 65. Wiring is provided in the
EconoMi$er IV wiring harness. See Fig. 60 on page 37. The out-
door enthalpy changeover set point is set with the outdoor enthal-
py set point potentiometer on the EconoMi$er IV controller.
When using this mode of changeover control, turn the enthalpy set
point potentiometer fully clockwise to the D setting. See Fig. 66
and 67.
39
® IV controller. The set
Changeover
Temperature
48°F
53°F
55°F
58°F
63°F
68°F
73°F
78°F
R