34
Specifications subject to change without notice.
34
SETUP AND CONFIGURATION
Before being placed into service, the W7220 economizer
module must be set up and configured for the installed
system.
The setup process uses a hierarchical menu structure that
is easy to use. Press the ▲ and ▼ arrow buttons to move
forward and backward through the menus and press the
button to select and confirm setup item changes.
TIME-OUT AND SCREENSAVER
When no buttons have been pressed for 10 minutes, the
LCD displays a screen saver, which cycles through the Sta
-
tus items. Each Status items displays in turn and cycles to
the next item after 5 seconds.
Enthalpy Settings
When the OA temperature, enthalpy and dew point are be
-
low the respective setpoints, the Outdoor Air can be used
for economizing. Figure 46 shows the new single enthalpy
boundaries in the W7220. There are 5 boundaries (set
-
points ES1 through ES5), which are defined by dry bulb
temperature, enthalpy and dew point.
Refer to Table 10 for ENTH CURVE setpoint values.
The W7220 calculates the enthalpy and dew point using the
OA temperature and humidity input from the OA enthalpy
sensor. When the OA temperature, OA humidity and
OA dew point are all below the selected boundary, the
economizer sets the economizing mode to YES, economiz
-
ing is available.
When all of the OA conditions are above the selected
boundary, the conditions are not good to economize and the
mode is set to NO.
Figure 46 shows the 5 current boundaries. There is also a
high limit boundary for differential enthalpy. The high limit
boundary is ES1 when there are no stages of mechanical
cooling energized and HL (high limit) when a compressor
stage is energized.
Fig. 46 — Single Enthalpy Curve Boundaries
Table 10 —
Single Enthalpy and Dual Enthalpy High Limit Curves
IMPORTANT: During setup, the economizer module is
live at all times.
ENTHALPY
CURVE
TEMP. DRY
BULB (F)
TEMP.
DEWPOINT (F)
ENTHALPY
(btu/lb/da)
POINT P1
POINT P2
TEMP. (F)
HUMIDITY
(%RH)
TEMP. (F)
HUMIDITY
(%RH)
ES1
80
60
28.0
80
36.8
66.3
80.1
ES2
75
57
26.0
75
39.6
63.3
80.0
ES3
70
54
24.0
70
42.3
59.7
81.4
ES4
65
51
22.0
65
44.8
55.7
84.2
ES5
60
48
20.0
60
46.9
51.3
88.5
HL
86
66
32.4
86
38.9
72.4
80.3
ECONOMIZING
AVAILABLE
NOT AVAILABLE
ENTHALPY
RA
HUM (%RH)
RA
TEMP
TEMPERATURE
ABSOLUTE HUMIDITY
ES5
ES4
ES3
ES2
ES1
HL
P1
(T,RH)
P2 (T,RH)
SINGLE ENTHALPY
DUAL ENTHALPY
HIGH LIMIT
Summary of Contents for RHW036-060
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