998659-YIM-C-0614
Johnson Controls Unitary Products
31
Enthalpy Settings
When the OA temperature, enthalpy and dew point are below
the respective setpoints, the Outdoor Air can be used for
economizing. Fig. 26 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 11 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. 26 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 11 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.
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.
Indoor Air Quality AQ
Indoor Air Quality (indoor sensor input): Terminal AQ accepts a
+2 to +10 Vdc signal with respect to the (AQ1) terminal. When
the signal is below it's set point, the actuator is allowed to
modulate normally in accordance with the enthalpy and mixed
air sensor inputs. When the AQ signal exceeds it's set point
setting and there is no call for free cooling, the actuator is
proportionately modulated from the 2 to 10 Vdc signal, with 2
Vdc corresponding to full closed and 10 Vdc corresponding to
full open. When there is no call for free cooling, the damper
position is limited by the IAQ Max damper position setting.
When the signal exceeds it's set point (Demand Control
Ventilation Set Point) setting and there is a call for free cooling,
the actuator modulates from the minimum position to the full
open position based on the highest call from either the mixed
air sensor input or the AQ voltage input.
• Optional CO
2
Space Sensor Kit Part # 2AQ04700324
• Optional CO
2
Sensor Kit Part # 2AQ04700424
Replace the top rear access panel on the unit.
Phasing
Predator
®
units are properly phased at the factory. Check for
proper compressor rotation. If the blower or compressors rotate
in the wrong direction at start-up, the electrical connection to
the unit is misphased. Change the phasing of the
Field Line
Connection at the factory or field supplied disconnect
to
obtain proper rotation. (Scroll compressors operate in only one
direction. If the scroll is drawing low amperage, has similar
suction and discharge pressures, or producing a high noise
level, the scroll is misphased.)
Blower Rotation
Check for proper supply air blower rotation. If the blower is
rotating backwards, the line voltage at the unit point of power
connection is misphased (See ‘PHASING’).
State
Fan Speed
OCC
Low
Y1
Low
Y2
High
W
High
Scroll compressors require proper rotation to operate
correctly. Units are properly phased at the factory. Do
not change the internal wiring to make the blower
condenser fans, or compressor rotate correctly.
Table 12: Supply Air Limitations
Unit Size (Ton)
Minimum
Maximum
078 (6.5)
1950
3250
090 (7.5)
2250
3750
102 (8.5)
2550
4250
120 (10)
3000
5000
150 (12.5)
3750
6250
