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INSTALLER'S GUIDE
Operation
(All Economizers)
Controller Dial Setting
Control set point scale is located on the Control Module,
see Figure 4 on page 2. Control points A, B, C, D are field
selectable, and are used for single enthalpy sensing.
The Solid State Enthalpy Sensor is used with a solid state
economizer control and damper actuator to proportion an
outdoor air damper in a ventilation system.
When using a single enthalpy control setpoint A, B, C,
or D combines temperature and humidity conditions re-
sulting in the control curve shown on the psychrometric
chart below.
When the enthalpy of the outdoor air is below (left of) the
appropriate curve, the outdoor air damper can proportion
open on a call for cooling. If the outdoor air enthalpy rises
above (right of) the control curve, the outdoor air damper
will close to minimum position.
q
page 8
CONTROL
CONTROL POINT
CURVE
APPROX. F ( C)
AT 50% RH
A
73 (23)
B
70 (21)
C
67 (19)
D
63 (17)
50
(10)
45
D
(7)
40
(4)
35
(2)
35
40
45
50
(2)
(4)
(7)
(10)
APPROXIMATE DRY BULB TEMPERATURE— F ( C)
1
HIGH LIMIT CURVE FOR W7459D.
For differential enthalpy, you must turn the control set
point past D (fully clockwise). Differential enthalpy is not
available for 101,102,103,104 Economizers.
If the outdoor air enthalpy is lower than the return air
enthalpy, the outdoor air damper will proportion open on
a call for cooling.
If the outdoor air enthalpy is higher than the return air
enthalpy, the outdoor air damper will close to minimum
position.
If the outdoor air enthalpy and return air enthalpy are
equal, the outdoor air damper will proportion open on a call
for cooling.
85
(29)
80
(27)
75
(24)
70
(21)
65
(18)
60
(16)
A
55
(13)
B
C
A
B
C
D
55
60
65
70
75
80
85
(13)
(16)
(18)
(21)
(24)
(27)
(29)
90
95
100
105
110
(32)
(35)
(38)
(41)
(43)
1
90
95
100
105
110
(32)
(35)
(38)
(41)
(43)
M11681
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