Enthalpy Settings; Two- -Speed Fan Operation - Bryant 549J Series Installation Instructions Manual

Table 20 – Enthalpy Operation No DCV (CO
Demand
Outside Air ---
Controlled
Good to
Ventilation
economize?
(DCV)
No
NO CO SENSOR
2
Yes
*
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.
[ 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.
Table 21 – Enthalpy Operation With DCV (CO
Demand
Outside Air ---
Controlled
Good to
Ventilation
economize?
(DCV)
No
Below set
Yes
No
Above set
Yes
*
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.
[ 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.

Enthalpy Settings

When the OA temperature, enthalpy and dew point are
below the respective setpoints, the outdoor air can be used
for economizing. Fig. 42 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 22 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,
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.
Fig. 42 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
Y1‐I Y2-I Fan Speed
Off Off Low
On Off Low
On On High
Off Off Low
On Off Low
On On High
Y1‐I Y2-I Fan Speed
Off Off Low
On Off Low
On On High
Off Off Low
On Off Low
On On High
Off Off Low
On Off Low
On On High
Off Off Low
On Off Low
On On High
Sensor) - - 2 Speed Fan
2
Y1-O Y2-O
0-v/Off 0-v/Off MIN POS L
24-v/On 0-v/Off MIN POS L
24-v/On 24-v/On MIN POS H
0-v/Off 0-v/Off MIN POS L
0-v/Off 0-v/Off MIN POS L to Full-Open
DELAY [
0-v/Off * MIN POS H to Full-Open
24-v/On
Sensor) - - 2 Speed Fan
2
Y1-O Y2-O
0-v/Off 0-v/Off VENTMIN L
24-v/On 0-v/Off VENTMIN L
24-v/On 24-v/On VENTMIN H
0-v/Off 0-v/Off VENTMIN L
0-v/Off 0-v/Off VENTMIN L to Full-Open
24-v/On 0-v/Off* VENTMIN H to Full-Open
0-v/Off 0-v/Off VENTMIN L to VENTMAX
24-v/On 0-v/Off VENTMIN L to VENTMAX
24-v/On 24-v/On VENTMIN H to VENTMAX
0-v/Off 0-v/Off VENTMIN L to VENTMAX
0-v/Off 0-v/Off VENTMIN L to Full-Open
DELAY [
0-v/Off* VENTMIN H to Full-Open
24-v/On
mechanical cooling energized and HL (high limit) when a
compressor stage is energized.
Table 22 provides the values for each boundary limit.

Two- -Speed Fan Operation

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.
State
OCC
Y1
Y2
W
The W (heating mode) is not controlled by the W7220 but
it requires the status to know where to position the OA
damper for minimum position for the fan speed.
36
Occupied Unoccupied
Closed
Closed
Closed
Closed
Closed to Full-Open
Closed to Full-Open
Occupied 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
Fan Speed
Low
Low
High
High