39
Fig. 60 — Outside Air Temperature Changeover
Set Points
Fig. 61 — 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. 62.)
Wiring is provided in the EconoMi$er IV wiring harness.
Fig. 62 — Return-Air Temperature or Enthalpy
Sensor Mounting Location
In this mode of operation, the outdoor-air temperature is com-
pared to the return-air temperature and the lower temperature
airstream is used for cooling. When using this mode of
changeover control, turn the enthalpy set point potentiometer
fully clockwise to the D setting. (See Fig. 59.)
Outdoor Enthalpy Changeover
For enthalpy control, accessory enthalpy sensor (part number
HH57AC078) is required. Replace the standard outdoor dry
bulb temperature sensor with the accessory enthalpy sensor in
the same mounting location. (See Fig. 62.) When the outdoor
air enthalpy rises above the outdoor enthalpy changeover set
point, the outdoor-air damper moves to its minimum position.
The outdoor enthalpy changeover set point is set with the out-
door enthalpy set point potentiometer on the EconoMi$er IV
controller. The set points are A, B, C, and D. (See Fig. 63.) The
factory-installed 620-ohm jumper must be in place across ter-
minals SR and SR+ on the EconoMi$er IV controller.
Fig. 63 — Enthalpy Changeover Set Points
Fig. 64 — EconoMi$er IV Control
Differential Enthalpy Control
For differential enthalpy control, the EconoMi$er IV controller
uses two enthalpy sensors (HH57AC078 and CRENT-
DIF004A00), one in the outside air and one in the return air
LED ON
LED ON
LED ON
LED ON
LED OFF
19
18
LED OFF
LED OFF
LED OFF
17
16
15
14
13
12
11
10
9
40
45
50
55
60
65
70
75
80
85
90
95
100
DEGREES FAHRENHEIT
mA
D
C
B
A
0
5
10
15
20
25
30
0.13 0.20 0.22 0.25 0.300.350.40 0.45 0.50
STATIC PRESSURE (in. wg)
FLOW IN CUBIC FEET PER MINUTE (cfm)
ECONOMI$ER IV
ECONOMI$ER IV
CONTROLLER
GROMMET
RETURN AIR
SENSOR
RETURN DUCT
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
20
2
2
2
4
2
6
28
3
0
32
3
4
3
6
38
40
4
2
4
4
4
6
9
0
1
0
0
80
7
0
60
50
4
0
30
2
0
1
0
E
NTHALPY 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
RELA
TI
VE HUMIDITY (%)
HIGH LIMIT
CURVE
TR1
24 Vac
COM
TR
24
Vac
HOT
12
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
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