Bryant LEGACY 580J*20M Series, Installation Instructions Manual

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37
Table 19 — Enthalpy Operation with DCV (CO
2
Sensor) — 2 Speed Fan
*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, en-
thalpy and dew point are below the respective setpoints, the Out-
door Air can be used for economizing. Figure 39 shows the new
single enthalpy boundaries in the W7220. There are 5 boundar-
ies (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 39 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 mechanical cooling
energized and HL (high limit) when a compressor stage is ener-
gized.
Table 20 provides the values for each boundary limit.
Fig. 39 — Single Enthalpy Curve Boundaries
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 24v/On 0v/Off*
VENTMIN to
Full-Open
Closed to Full-Open
ECONOMIZING
AVAILABLE
NOT AVAILABLE
ENTHALPY
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