Carrier 50HCQA04-06 Installation Instructions Manual page 41

Table 15 — Enthalpy Operation with DCV (CO
DEMAND OUTSIDE AIR
CONTROLLED
VENTILATION (DCV) ECONOMIZE
Below CO Set
2
Above CO Set
2
*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 calls for Y1-I and
Y2-I have not been satisfied.
ENTHALPY TEMP. DRY
CURVE BULB (F)
ES1 80
ES2 75
ES3 70
ES4 65
ES5 60
HL 86
Enthalpy Settings
When the OA temperature, enthalpy and dew point are below
the respective setpoints, the Outdoor Air can be used for econ-
omizing. Fig. 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 16 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.
GOOD TO 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
Table 16 — Single Enthalpy and Dual Enthalpy High Limit Curves
TEMP. ENTHALPY
DEWPOINT (F) (btu/lb/da)
60
57
54
51
48
66
Sensor) — 1 Speed Fan
2
FAN
Y1-O Y2-O
SPEED
HIGH 0v/Off 0v/Off
HIGH 24v/On 0v/Off
HIGH 24v/On 24v/On
HIGH 0v/Off 0v/Off
HIGH 0v/Off 0v/Off
HIGH 24v/On 0v/Off
HIGH 0v/Off 0v/Off
HIGH 24v/On 0v/Off
HIGH 24v/On 24v/On
HIGH 0v/Off 0v/Off
HIGH 0v/Off 0v/Off
HIGH 24v/On 0v/Off*
POINT P1
TEMP. (F)
28.0 80
26.0 75
24.0 70
22.0 65
20.0 60
32.4 86
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.
Fig. 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.
41
OCCUPIED UNOCCUPIED
VENTMIN
VENTMIN
VENTMIN
VENTMIN
VENTMIN to
Closed to Full-Open
Full-Open
VENTMIN to
Closed to Full-Open
Full-Open
VENTMIN to
VENTMAX
VENTMIN to
VENTMAX
VENTMIN to
VENTMAX
VENTMIN to
VENTMAX
VENTMIN to
Closed to Full-Open
Full-Open
VENTMIN to
Closed to Full-Open
Full-Open
POINT P2
HUMIDITY
TEMP. (F)
(%RH)
36.8 66.3
39.6 63.3
42.3 59.7
44.8 55.7
46.9 51.3
38.9 72.4
Closed
Closed
Closed
Closed
Closed
Closed
Closed
Closed
HUMIDITY
(%RH)
80.1
80.0
81.4
84.2
88.5
80.3