45
Enthalpy Settings
When the OA temperature, enthalpy and dew point are below
the respective setpoints, the Outdoor Air can be used for econ-
omizing. Figure 69 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 ENTH CURVE setpoint values.
The W7220 calculates the enthalpy and dew point using the
OA temperature and humidity input from the OA enthalpy sen-
sor. 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 bound-
ary, the conditions are not good to economize and the mode is
set to NO.
Figure 69 shows the 5 current boundaries. There is also a high
limit boundary for differential enthalpy. The high limit bound-
ary is ES1 when there are no stages of mechanical cooling en-
ergized and HL (high limit) when a compressor stage is
energized.
Fig. 69 — Single Enthalpy Curve Boundaries
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
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
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
Summary of Contents for 551K 04N Series
Page 15: ...15 Fig 27 Condenser Fan Assembly Screw Pattern Sequence 1 2 3 4 5 NO SCREW Blank Tab ...
Page 82: ...82 APPENDIX D WIRING DIAGRAMS Fig E 551K 04 06 208 230 1 60 Unit with RTU Open Controller ...
Page 83: ...83 APPENDIX D WIRING DIAGRAMS Fig F 551K 04 06 208 230 3 60 Unit with RTU Open Controller ...
Page 84: ...84 APPENDIX D WIRING DIAGRAMS Fig G 551K 04 06 460 575 3 60 Unit with RTU Open Controller ...
Page 85: ...85 APPENDIX D WIRING DIAGRAMS Fig H 551K 04 06 Power Wiring Diagram 208 230 1 60 ...
Page 86: ...86 APPENDIX D WIRING DIAGRAMS Fig I 551K 04 06 Power Wiring Diagram 208 230 3 60 ...
Page 87: ...87 APPENDIX D WIRING DIAGRAMS Fig J 551K 04 06 Power Wiring Diagram 460 575 3 60 ...
Page 89: ......
