43
Table 18 — Enthalpy Operation, No Demand Controlled Ventilation (DCV) (CO
2
Sensor) — 2 Speed Fan
*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, second
stage of mechanical cooling Y2-O can be turned on after the delay if the
calls for Y1-I and Y2-I have not been satisfied.
Table 19 — Enthalpy Operation, with Demand Controlled Ventilation (DCV) (CO
2
Sensor) — 2 Speed Fan
*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, second
stage of mechanical cooling Y2-O can be turned on after the delay if the
calls for Y1-I and Y2-I have not been satisfied.
Table 20 — Single Enthalpy and Dual Enthalpy High Limit Curves
Enthalpy Settings
When the OA temperature, enthalpy and dew point are below
the respective setpoints, the Outdoor Air can be used for econ-
omizing. Figure 50 shows the new single enthalpy boundaries
in the W7220. There are 5 boundaries (setpoints ES1 through
ES5), which are defined by dry bulb temperature, enthalpy and
dew point.
Refer to Table 20 for ENTH CURVE setpoint values.
The W7220 calculates the enthalpy and dew point using the
OA temperature and humidity input from the OA enthalpy sen-
sor. When the OA temperature, OA humidity and OA dew
point are all below the selected boundary, the economizer sets
the economizing mode to YES, economizing is available.
When all of the OA conditions are above the selected bound-
ary, the conditions are not good to economize and the mode is
set to NO.
Figure 50 shows the 5 current boundaries. There is also a high
limit boundary for differential enthalpy. The high limit bound-
ary is ES1 when there are no stages of mechanical cooling en-
ergized and HL (high limit) when a compressor stage is
energized.
DCV
OUTSIDE AIR
GOOD TO
ECONOMIZE?
Y1-I Y2-I FAN SPEED Y1-O Y2-O OCCUPIED UNOCCUPIED
None
No
Off Off Low 0-v/Off 0-v/Off MIN POS L Closed
On Off Low 24-v/On 0-v/Off MIN POS L Closed
On On High 24-v/On 24-v/On MIN POS H Closed
Yes
Off Off Low 0-v/Off 0-v/Off MIN POS L Closed
On Off Low 0-v/Off 0-v/Off MIN POS L to Full-Open Closed to Full-Open
On On High
DELAY*
24-v/On
0-v/Off
†
MIN POS H to Full-Open Closed to Full-Open
DCV
OUTSIDE AIR
GOOD TO
ECONOMIZE?
Y1-I Y2-I FAN SPEED Y1-O Y2-O OCCUPIED UNOCCUPIED
Below Set
No
Off Off Low 0-v/Off 0-v/Off VENTMIN L Closed
On Off Low 24-v/On 0-v/Off VENTMIN L Closed
On On High 24-v/On 24-v/On VENTMIN H Closed
Yes
Off Off Low 0-v/Off 0-v/Off VENTMIN L Closed
On Off Low 0-v/Off 0-v/Off VENTMIN L to Full-Open Closed to Full-Open
On On High 24-v/On 0-v/Off
†
VENTMIN H to Full-Open Closed to Full-Open
Above Set
No
Off Off Low 0-v/Off 0-v/Off VENTMIN L to VENTMAX Closed
On Off Low 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 Low 0-v/Off 0-v/Off VENTMIN L to VENTMAX Closed
On Off Low 0-v/Off 0-v/Off VENTMIN L to Full-Open Closed to Full-Open
On On High
DELAY*
24-v/On
0-v/Off
†
VENTMIN H to Full-Open Closed to Full-Open
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
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