Enthalpy Settings; Two-Speed Fan Operation - Carrier Legacy 548J07 Installation Instructions Manual

DEMAND OUTSIDE AIR
CONTROLLED GOOD TO
VENTILATION (DCV) ECONOMIZE
Below CO Set
2
Above CO Set
2
*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 sec-
ond 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 econ-
omizing. Figure 50 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 23 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 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.

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
using 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 position, see Table 22.
Table 21 — Enthalpy Operation with DCV (CO
Y1-I Y2-I
OFF OFF
No ON OFF
ON ON
OFF OFF
ON OFF
Yes
ON ON
OFF OFF
No ON OFF
ON ON
OFF OFF
Yes ON OFF
ON ON
Sensor) — 2 Speed Fan
2
FAN
Y1-O Y2-O
SPEED
LOW 0v/Off 0v/Off
LOW 24v/On 0v/Off
HIGH 24v/On 24v/On
LOW 0v/Off 0v/Off
LOW 0v/Off 0v/Off
HIGH 24v/On 0v/Off
LOW 0v/Off 0v/Off
LOW 24v/On 0v/Off
HIGH 24v/On 24v/On
LOW 0v/Off 0v/Off
LOW 0v/Off 0v/Off
DELAY*
HIGH 0v/Off*
24v/On
STATE
OCC
Y1
Y2
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 pro-
grammed 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 Advanced 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.
38
OCCUPIED
VENTMIN
VENTMIN
VENTMIN
VENTMIN
VENTMIN to
Full-Open
VENTMIN to
Full-Open
VENTMIN to
VENTMAX
VENTMIN to
VENTMAX
VENTMIN to
VENTMAX
VENTMIN to
VENTMAX
VENTMIN to
Full-Open
VENTMIN to
Full-Open
Table 22 — Fan Speed
FAN SPEED
W
UNOCCUPIED
Closed
Closed
Closed
Closed
Closed to Full-Open
Closed to Full-Open
Closed
Closed
Closed
Closed
Closed to Full-Open
Closed to Full-Open
Low
Low
High
High