Bryant 580J*16D Series, Руководство по установке

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Table 22 — Single Enthalpy and Dual Enthalpy High Limit Curves
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. Fig. 65 shows the new sin-
gle enthalpy boundaries in the W7220. There are 5 boundaries
(setpoints ES1 through ES5), which are defined by dry bulb tem-
perature, 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 econo-
mizing 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.
Fig. 65 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 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, see Table 23.
Table 23 — Fan Speed
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 con-
troller.
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.
Fig. 65 — Single Enthalpy Curve Boundaries
ENTHALPY
CURVE
TEMP. DRY
BULB (F)
TEMP.
DEWPOINT (F)
ENTHALPY
(btu/lb/da)
POINT P1 POINT P2
TEMP. (F)
HUMIDITY
(%RH)
TEMP. (F)
HUMIDITY
(%RH)
ES1 80 60 28.0 80 36.8 66.3 80.1
ES2 75 57 26.0 75 39.6 63.3 80.0
ES3 70 54 24.0 70 42.3 59.7 81.4
ES4 65 51 22.0 65 44.8 55.7 84.2
ES5 60 48 20.0 60 46.9 51.3 88.5
HL 86 66 32.4 86 38.9 72.4 80.3
STATE FAN SPEED
OCC Low
Y1 Low
Y2 High
W High
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