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provided in the EconoMi$er IV wiring harne ss. (See Fig.
38.)
ECONOMI$ERIV
ECONOMI$ERIV
CONTROLLER
GROMMET
RETURN AIR
SENSOR
RETURN DUCT
(FIELD-PROVIDED)
C07085
Fig. 48 -- Return Air Temperature or Enthalpy Sensor
Mounting Location
In this mode of operation, the outdoor-air temperature i s
compared to the return-air temperature and the lower
temperature airstre am is used for cooling. When using this
mode of changeover control, turn the entha lpy setpoint
potentiometer fully clockwise to the D setting. (See Fig.
45.)
Outdoor Enthalpy Changeover
For enthalpy control, accessory enthalpy sensor (part
number HH57AC078) is required. Replace the standard
outdoor dry bulb temperature sensor with the accessory
entha lpy sensor in the same mounting location. (See Fig.
39.) When the outdoor air enthalpy rises above the
outdoor enthalpy changeover setpoint, the outdoor-air
dampe r moves to its minimum position. The outdoor
entha lpy changeover setpoint is set with the outdoor
entha lpy setpoint potent iometer on the EconoMi$er IV
controller. The setpoints are A, B, C, and D. (See Fig. 46.)
The factory-i nstalled 620-ohm jumper must be in place
across terminals S
R
and SR+ on the EconoMi$er IV
controller.
Differential Enthalpy Control
For differential enthalpy control, t he EconoMi$er IV
controller uses two enthalpy sensors (HH57AC078 and
CRENTDIF004A00), one in the outside air and one in the
return air duct. The EconoMi$er IV controller compares
the outdoor air enthalpy to the return air entha lpy to
determine EconoMi$er IV use. The controller selects the
lower ent halpy air (return or outdoor) for cooling. For
exam ple, when the outdoor air has a lower e nthalpy than
the return air, the EconoMi$er IV opens to bring in
outdoor air for free cooling.
Replace the standard outside air dry bulb temperature
sensor with the accessory enthalpy sensor in the same
mounting location. (See Fig. 39.) Mount the return air
enthalpy sensor in the return air duct. (See Fig. 48.)
Wiring is provided in the EconoMi$er IV wiring harness.
(See Fig. 41.) The outdoor enthalpy changeover setpoint is
set with the outdoor enthalpy setpoint potentiometer on
the EconoMi$er IV controller. When using this mode of
change over control, turn the enthalpy setpoint
potentiometer fully clockwise to the D setting.
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. 49 -- Enthalpy Changeover Setpoints
580J