53
*With 2SP FAN DELAY (Advanced Setup Menu) when in the economizing mode there is a delay for the high speed fan to try to satisfy the call for second
stage cooling by turning on the fan to high and opening the OA damper 100% before the first stage mechanical cooling is enabled.
†With stage 3 delay (STG3 DLY) in Advanced setup menu can turn on second stage of mechanical cooling Y2–O after the delay if the call for Y1–I and
Y2–I have not been satisfied.
ENTHALPY SETTINGS
When the OA temperature, enthalpy and dew point are below the
respective set points, the Outdoor Air can be used for economiz-
ing. Figure 71 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 26 for ENTH CURVE set point 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 econo-
mizing mode to YES, economizing 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 71 shows the 5 current boundaries. There is also a high lim-
it 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. 71 — Single Enthalpy Curve Boundaries
Table 25 — Enthalpy Operation with DCV (CO
2
Sensor) — 1 Speed Fan
DEMAND
CONTROLLED
VENTILATION (DCV)
OUTSIDE AIR
GOOD TO
ECONOMIZE
Y1-I Y2-I
FAN
SPEED
Y1-O Y2-O OCCUPIED UNOCCUPIED
Below CO
2
set
No
Off Off High 0-v/Off 0-v/Off VENTMIN Closed
On Off High 24-v/On 0-v/Off VENTMIN Closed
On On High 24-v/On 24-v/On VENTMIN Closed
Yes
Off Off High 0-v/Off 0-v/Off VENTMIN Closed
On Off High 0-v/Off 0-v/Off
VENTMIN to
Full-Open
Closed to
Full-Open
On On High 24-v/On 0-v/Off†
VENTMIN to
Full-Open
Closed to
Full-Open
Above CO
2
set
No
Off Off High 0-v/Off 0-v/Off
VENTMIN to
VENTMAX
Closed
On Off High 24-v/On 0-v/Off
VENTMIN L to
VENTMAX
Closed
On On High 24-v/On 24-v/On
VENTMIN H to
VENTMAX
Closed
Yes
Off Off High 0-v/Off 0-v/Off
VENTMIN L to
VENTMAX
Closed
On Off High 0-v/Off 0-v/Off
VENTMIN to
Full-Open
Closed to
Full-Open
On On High
DELAY*
24-v/On
0-v/Off†
VENTMIN to
Full-Open
Closed to
Full-Open
ECONOMIZING
AVAILABLE
NOT AVAILABLE
ENTHA
LPY
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
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