Carrier 48TC series, Service And Maintenance Instructions, Page: 52 / 112

52
turn the enthalpy setpoint potentiometer fully clockwise to the D
setting. (See Fig. 69.)
Fig. 71 — Return-Air Temperature or Enthalpy
Sensor Mounting Location
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. 71.) When the outdoor air enthalpy
rises above the outdoor enthalpy changeover setpoint, the outdoor-
air damper moves to its minimum position. The outdoor enthalpy
changeover setpoint is set with the outdoor enthalpy setpoint po -
tentiometer on the EconoMi$er IV controller. The setpoints are A,
B, C, and D. (See Fig. 72.) The factory-installed 620-ohm jumper
must be in place across terminals SR and SR+ on the EconoMi$er
IV controller (see Fig. 73).
Fig. 72 — Enthalpy Changeover Setpoints
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 duct and one in the return-air
duct. The EconoMi$er IV controller compares the outdoor air en -
thalpy to the return air enthalpy to determine EconoMi$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$er IV opens to bring in outdoor
air for free cooling.
Replace the standard outside air dry bulb temperature sensor with
the accessory enthalpy sensor in the same mounting location. See
Fig. 61. Mount the return air enthalpy sensor in the return air duct.
See Fig. 71. Wiring is provided in the EconoMi$er IV wiring har -
ness. See Fig. 64. The outdoor enthalpy changeover setpoint is set
with the outdoor enthalpy setpoint potentiometer on the
EconoMi$er IV controller. When using this mode of changeover
control, turn the enthalpy setpoint potentiometer fully clockwise to
the D setting.
INDOOR AIR QUALITY (IAQ) SENSOR INPUT
The IAQ input can be used for demand controlled ventilation con
-
trol based on the level of CO
2
measured in the space or return air
duct.
Mount the accessory IAQ sensor according to manufacturer speci -
fications. The IAQ sensor should be wired to the AQ and AQ1 ter -
minals of the controller. Adjust the DCV potentiometers to corre -
spond to the DCV voltage output of the indoor air quality sensor at
the user-determined setpoint. See Fig. 74.
If a separate field-supplied transformer is used to power the IAQ
sensor, the sensor must not be grounded or the EconoMi$er IV
control board will be damaged.
When using demand controlled ventilation, the minimum damper
position represents the minimum ventilation position for VOC
(volatile organic compounds) ventilation requirements. The maxi -
mum demand ventilation position is used for fully occupied venti -
lation.
When demand controlled ventilation control is not being used, the
minimum position potentiometer should be used to set the occu -
pied ventilation position. The maximum demand ventilation posi -
tion should be turned fully clockwise.
ECONOMI$ER IV
ECONOMI$ER IV
CONTROLLER
GROMMET
RETURN AIR
SENSOR
RETURN DUCT
(FIELD-PROVIDED)
CONTROL
CURVE
A
B
C
D
CONTROL POINT
APPROX. deg. F (deg. C)
AT 50% RH
73 (23)
70 (21)
67 (19)
63 (17)
12
14
16
1
8
20
2
2
2
4
2
6
28
30
32
3
4
3
6
38
40
4
2
4
4
46
9
0
1
0
0
80
7
0
60
50
40
30
20
10
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
RELATI
VE HUMI
DI
TY (
%)
HIGH LIMIT
CURVE
APPROXIMATE DRY BULB TEMPERATURE--degrees F (degrees C)
TR1
24 Vac
COM
TR
24
Vac
HOT
1 2
3
4
5
EF EF1
+
_
P1
T1
P
T
N
EXH
2V 10V
EXH
Set
Set
2V 10V
2V 10V
DCV
DCV
Free
Cool
B
C
A
D
SO+
SR+
SR
SO
AQ1
AQ
DCV
Min
Pos
Open
Max
N1