Carrier WeatherMaster 50HC04 Service And Maintenance Instructions page 37

19
LED ON
18
D
17
LED ON
16 LED OFF
15
14
LED OFF
13
12
11
10
9
40 45 50 55 60
DEGREES FAHRENHEIT
Fig. 70 — Outside Air Temperature Changeover
Set Points
30
25
20
15
10
5
0
0.13 0.20 0.22
STATIC PRESSURE (in. wg)
Fig. 71 — Outdoor-Air Damper Leakage
DIFFERENTIAL DRY BULB CONTROL
For differential dry bulb control the standard outdoor dry bulb
sensor is used in conjunction with an additional accessory dry
bulb sensor (P/N: CRTEMPSN002A00). The accessory sensor
must be mounted in the return airstream. See Fig. 72. Wiring is
provided in the EconoMi$er IV wiring harness.
In this mode of operation, the outdoor-air temperature is com-
pared to the return-air temperature and the lower temperature
airstream is used for cooling. When using this mode of change-
over control, turn the enthalpy set point potentiometer fully
clockwise to the D setting. See Fig. 69.
OUTDOOR ENTHALPY CHANGEOVER
For enthalpy control, accessory enthalpy sensor (P/N:
HH57AC078) is required. Replace the standard outdoor dry
bulb temperature sensor with the accessory enthalpy sensor in
the same mounting location. See Fig. 73. When the outdoor air
enthalpy rises above the outdoor enthalpy changeover set
point, the outdoor-air damper moves to its minimum position.
The outdoor enthalpy changeover set point is set with the out-
door enthalpy set point potentiometer on the EconoMi$er IV
controller. The set points are A, B, C, and D. See Fig. 74. The
factory-installed 620-ohm jumper must be in place across ter-
minals S and SR+ on the EconoMi$er IV controller.
R
C
LED ON
B
LED ON
LED OFF
A
LED OFF
65 70 75 80 85 90
0.25 0.30 0.35 0.40 0.45
ECONOMI$ER IV
100
95
Fig. 72 — Return Air Temperature or Enthalpy Sensor
N1
N
P1
P
T1
T
0.50
AQ1
AQ
SO+
SO
SR+
SR
Fig. 73 — EconoMi$er IV Control
DIFFERENTIAL ENTHALPY CONTROL
For differential enthalpy control, the EconoMi$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$er IV opens to
bring in outdoor air for free cooling.
Replace the standard outside air dry bulb temperature sensor
with the accessory enthalpy sensor in the same mounting loca-
tion. See Fig. 73. Mount the return air enthalpy sensor in the
return air duct. See Fig. 72. Wiring is provided in the
EconoMi$er IV wiring harness. See Fig. 65. The outdoor en-
thalpy changeover set point is set with the outdoor enthalpy set
point potentiometer on the EconoMi$er IV controller. When
using this mode of changeover control, turn the enthalpy set
point potentiometer fully clockwise to the D setting.
37
RETURN DUCT
(FIELD-PROVIDED)
Mounting Location
EXH
Set
2V 10V
EXH
Min
Pos
Open
DCV
Max
2V 10V
DCV
DCV
Set
2V 10V
Free
Cool
B C
D
A
ECONOMI$ER IV
CONTROLLER
GROMMET
RETURN AIR
SENSOR
TR TR1
24 24 Vac
Vac
COM
HOT
_
+
1 2
5
4
3
EF EF1