JADE™ ECONOMIZER MODULE
63-2700—11
30
Fig. 22. Single Enthalpy curve and boundaries.
Enthalpy Settings
When the OA temperature, enthalpy and dew point are
below the respective setpoints, the Outdoor Air can be
used for economizing. Fig. 22 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 15 for the ENTH CURVE setpoint values.
To use enthalpy the W7220 must have a C7400S Sylkbus
sensor for OA. The W7220 calculates the enthalpy and
dew point using the OA temperature and humidity input
from the OA 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 conditions are above the selected boundary, the
conditions are not good to economize and the mode is set
to NO.
Fig. 22 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 when a compressor
stage is energized.
Table 15 provides the values for each boundary limit.
Two-Speed Fan Operation
The later versions of the W7220 Jade controller have 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.
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.
The 2 speed fan delay is available when the system is
programmed 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
Table 15. Single Enthalpy and Dual Enthalpy High Limit Curves.
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
80.0
60.0
28.0
80.0
36.8
66.3
80.1
ES2
75.0
57.0
26.0
75.0
39.6
63.3
80.0
ES3
70.0
54.0
24.0
70.0
42.3
59.7
81.4
ES4
65.0
51.0
22.0
65.0
44.8
55.7
84.2
ES5
60.0
48.0
20.0
60.0
46.9
51.3
88.5
HL
86.0
66.0
32.4
86.0
38.9
72.4
80.3
ECONOMIXING
AVAILABLE
NOT AVAILABLE
TEMPERATURE
ABSOLUTE HUMIDITY
RA TEMP
RA
HU
M (
%R
H)
ENTHALPY
ES4
ES3
ES2
ES1
HL
P2 (T,RH)
DUAL ENTHALPY
HIGH LIMIT
SINGLE ENTHALPY
ES5
P1
(T,RH)
M32286A
State
Fan Speed
OCC
Low
Y1
Low
Y2
High
W
High