38
*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 51 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 22 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 51 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.
TWO-SPEED FAN OPERATION
NOTE: Two-Speed Fan operation applies to size 07 models only.
The W7220 controller has the capability to work with a system us-
ing a 2-speed supply fan. The W7220 does not control the supply
directly but uses the following input status to determine the speed
of the supply fan and controls the OA damper to the required posi-
tion, see Table 21.
The W (heating mode) is not controlled by the W7220 but it re-
quires the status to know where to position the OA damper for
minimum position for the fan speed.
The 2 speed fan delay is available when the system is programmed
for 2 speed fan (in the System Setup menu item). The 2 speed fan
delay is defaulted to 5 minutes and can be changed in the Ad-
vanced Setup menu item. When the unit has a call for Y1 In and in
the free cooling mode and there is a call for Y2 In, the 2-speed fan
delay starts and the OA damper will modulate 100% open, the
supply fan should be set to high speed by the unit controller.
After the delay one of two actions will happen:
• The Y2 In call will be satisfied with the damper 100%
open and fan on high speed and the call will turn off
OR
• If the call for additional cooling in the space has not been
satisfied then the first stage of mechanical cooling will be
enabled through Y1 Out or Y2 Out.
Table 20 — Enthalpy Operation with DCV (CO
2
Sensor) — 2 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
LOW
0v/Off
0v/Off
VENTMIN
Closed
ON
OFF
LOW
24v/On
0v/Off
VENTMIN
Closed
ON
ON
HIGH
24v/On
24v/On
VENTMIN
Closed
Yes
OFF
OFF
LOW
0v/Off
0v/Off
VENTMIN
Closed
ON
OFF
LOW
0v/Off
0v/Off
VENTMIN to
Full-Open
Closed to Full-Open
ON
ON
HIGH
24v/On
0v/Off
VENTMIN to
Full-Open
Closed to Full-Open
Above CO
2
Set
No
OFF
OFF
LOW
0v/Off
0v/Off
VENTMIN to
VENTMAX
Closed
ON
OFF
LOW
24v/On
0v/Off
VENTMIN to
VENTMAX
Closed
ON
ON
HIGH
24v/On
24v/On
VENTMIN to
VENTMAX
Closed
Yes
OFF
OFF
LOW
0v/Off
0v/Off
VENTMIN to
VENTMAX
Closed
ON
OFF
LOW
0v/Off
0v/Off
VENTMIN to
Full-Open
Closed to Full-Open
ON
ON
HIGH
DELAY*
24v/On
0v/Off*
VENTMIN to
Full-Open
Closed to Full-Open
Table 21 — Fan Speed
STATE
FAN SPEED
OCC
Low
Y1
Low
Y2
High
W
High
