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47
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 economizing mode to YES,
economizing is available.
When all of the OA conditions are above the selected
boundary, the conditions are not good to economize and
the mode is set to NO.
Fig. 57 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 12 provides the values for each boundary limit.
TEMPERATURE
ENTHALPY
RA
TEMP
ABSOLUTE HUMIDITY
ECONOMIXING
AVAILABLE
NOT AVAILABLE
ES5
ES4
ES3
ES2
ES1
HL
DUAL ENTHALPY
HIGH LIMIT
SINGLE ENTHALPY
P2 (T,RH)
P1
(T,RH)
RA
H
UM
(%
RH
)
C12015
Fig. 57 -- Single Enthalpy Curve and Boundaries
Table 12 – Single Enthalpy and Dual Enthalpy High Limit Curves (EN Units)
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
Summary of Contents for 50LC 07
Page 9: ...9 COOLING CHARGING CHARTS C150169 Fig 9 Cooling Charging Charts 07 ...
Page 10: ...10 COOLING CHARGING CHARTS C150172 Fig 10 Cooling Charging Charts 08 ...
Page 11: ...11 COOLING CHARGING CHARTS C150170 Fig 11 Cooling Charging Charts 09 ...
Page 12: ...12 COOLING CHARGING CHARTS C150171 Fig 12 Cooling Charging Charts 12 ...
Page 27: ...27 C150181 Fig 34 50LC 07 Control Wiring Diagram ...
Page 28: ...28 C150225 Fig 35 50LC 07 RTU Open Control Wiring Diagram ...
Page 29: ...29 C14095 Fig 36 50LC 07 Power Wiring Diagram 208 230V 460V and 575V Units ...
Page 30: ...30 C14013 Fig 37 50LC 08 12 Control Wiring Diagram ...
Page 31: ...31 C14104 Fig 38 50LC 08 12 RTU Open Control Wiring Diagram ...
Page 32: ...32 C14105 Fig 39 50LC 08 12 Power Wiring Diagram 208 230V Units ...
Page 33: ...33 C150216 Fig 40 50LC 08 12 Power Wiring Diagram 460V 575V Units ...
Page 57: ...57 C13683 Fig 62 Typical EconoMi er X Wiring Diagram ...