Carrier 48TC*D08 - Page 61

61
Differential Dry Bulb Control
For differenti al 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 ai rstream. (See Fig. 80.) Wiring is
provided in the Ec onoMi$er IV wiring harness. (See Fig.
73.)
ECONOMI$ERIV
ECONOMI$ERIV
CONTROLLER
GROMMET
RETURN AIR
SENSOR
RETURN DUCT
(FIELD-PROVIDED)
C07085
Fig. 80 -- Return Air Temperature or Enthalpy Sensor
Mounting Location
In this mode of operati on, the outdoor-air temperature is
compared to the return-air temperature and the lower
temperature airstream is used for cooling. When using this
mode of change over control, turn the enthalpy setpoint
potentiometer fully clockwise to the D setting. (See Fig.
77.)
Outdoor Enthalpy Changeover
For enthalpy control, accessory enthalpy sensor (part
number HH57AC078) is required. Replace the standard
outdoor dry bulb temperature sensor with the accessory
entha lpy sensor in the same mounting location. (See Fig.
80.) W hen the outdoor air enthalpy rises above the
outdoor enthalpy changeover setpoint, the outdoor-air
dampe r moves to its minim um position. The outdoor
entha lpy changeover setpoint is set with the out door
entha lpy setpoint potentiometer on the EconoMi$er IV
controller. The setpoints are A, B, C, and D. (See Fig. 81.)
The factory-installed 620-ohm jumper must be in place
across terminals S
R
and SR+ on the EconoMi$er IV
controller.
CONTROL
CURVE
A
B
C
D
CONTROL POINT
APPROX.
deg. F (deg. C)
AT 50% RH
73 (23)
70 (21)
67 (19)
63 (17)
1
2
1
4
1
6
1
8
2
0
2
2
2
4
26
28
30
32
3
4
3
6
3
8
40
42
4
4
46
9
0
1
0
0
80
70
6
0
50
4
0
30
20
1
0
ENTHALPY BTU PER POUND DRY AIR
85
(29)
90
(32)
95
(35)
100
(38)
105
(41)
110
(43)
35
(2)
35
(2)
40
(4)
40
(4)
105
(41)
110
(43)
45
(7)
45
(7)
50
(10)
50
(10)
55
(13)
55
(13)
60
(16)
60
(16)
65
(18)
65
(18)
70
(21)
70
(21)
75
(24)
75
(24)
80
(27)
80
(27)
85
(29)
90
(32)
95
(35)
100
(38)
A
A
B
B
C
C
D
D
RELATIVE HUMIDITY (%)
HIGH LIMIT
CURVE
APPROXIMATE DRY BULB TEMPERATURE--degrees F (degrees C)
C06037
Fig. 81 -- Enthalpy Changeover Setpoints
48TC