Carrier 50KC04-06 Service And Maintenance Instructions page 34

30
25
20
15
10
5
0
0.13 0.20 0.22
STATIC PRESSURE (in. wg)
Fig. 52 — 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 (part number CRTEMPSN002A00). The accessory
sensor must be mounted in the return airstream. (See Fig. 53.)
Wiring is provided in the EconoMi$er IV wiring harness.
ECONOMI$ER IV
Fig. 53 — Return-Air Temperature or Enthalpy
Sensor Mounting Location
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. 50.)
Outdoor Enthalpy Changeover
For enthalpy control, accessory enthalpy sensor (part number
HH57AC078) is required. Replace the standard outdoor dry
bulb temperature sensor with the accessory enthalpy sensor in
the same mounting location. (See Fig. 53.) 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$er IV
controller. The set points are A, B, C, and D. (See Fig. 54.) The
factory-installed 620-ohm jumper must be in place across ter-
minals SR and SR+ on the EconoMi$er IV controller.
0.25 0.30 0.35 0.40 0.45
ECONOMI$ER IV
CONTROLLER
GROMMET
RETURN AIR
SENSOR
RETURN DUCT
(FIELD-PROVIDED)
CONTROL
CONTROL POINT
CURVE
APPROX. deg. F (deg. C)
AT 50% RH
A 73 (23)
B 70 (21)
C 67 (19)
D 63 (17)
0.50
40
(4)
35
(2)
35 40
(2) (4)
APPROXIMATE DRY BULB TEMPERATURE--degrees F (degrees C)
Fig. 54 — Enthalpy Changeover Set Points
N1
N
P1
P
T1
T
AQ1
AQ
SO+
SO
SR+
SR
Fig. 55 — EconoMi$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. 42.) Mount the return air enthalpy sensor in the
return air duct. (See Fig. 53.) Wiring is provided in the
EconoMi$er IV wiring harness. (See Fig. 42.) The outdoor en-
thalpy changeover set point is set with the outdoor enthalpy set
point potentiometer on the EconoMi$er IV controller. When
using this mode of changeover control, turn the enthalpy set
point potentiometer fully clockwise to the D setting.
34
85 90
(29) (32)
80
(27)
75
(24)
70
(21)
65
(18)
60
(16)
A
55
(13)
B
50
C
(10)
45 D
(7)
A
B
C
D
45 50 55 60 65 70 75 80 85 90
(7) (10) (13) (16) (18) (21) (24) (27) (29) (32)
EXH
Set
2V 10V
EXH
Min
Pos
Open
DCV
Max
2V 10V
DCV
DCV
Set
2V 10V
Free
Cool
B C
D
A
95 100 105 110
(35) (38) (41) (43)
HIGH LIMIT
CURVE
95 100 105 110
(35) (38) (41) (43)
TR1
TR
24 24 Vac
Vac
COM
HOT
_
+
1 2
5
4
3
EF1
EF