5188235-YIM-B-1016
42
Johnson Controls Unitary Products
Enthalpy Settings
When the OA temperature, enthalpy and dew point are below
the respective setpoints, the Outdoor Air can be used for
economizing. Fig. 29 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 13 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. 29 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 13 provides the values for each boundary limit.
Indoor Air Quality - IAQ
Indoor Air Quality (indoor sensor input): The Indoor Air Quality
sensor is connected to the economizer board through the IAQ
analog input terminal and the associated COM and 24V~ inputs
on the economizer board. Terminal IAQ accepts a 0 to +10 Vdc
signal with respect to the (IAQ) terminal. When the signal is
below its set point, the actuator is allowed to modulate normally
in accordance with the enthalpy and mixed air sensor inputs.
When the IAQ signal exceeds its set point setting, and there is
no call for free cooling, the actuator is proportionately
modulated from the 0 to 10 Vdc signal, with 0 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 its 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 IAQ voltage input.
• Optional CO2 Space Sensor Kit Part #2AQ04700524
• Optional CO2 Sensor Kit Part #2AQ04700624
Phasing
ZE 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.)
Table 13: 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
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.