48
ENTHALPY SETTINGS
When the OA temperature, enthalpy and dew point are below the
respective set points, the Outdoor Air can be used for economiz-
ing. Figure 62 shows the new single enthalpy boundaries in the
W7220. There are 5 boundaries (set points ES1 through ES5),
which are defined by dry bulb temperature, enthalpy and dew
point.
Refer to Table 18 for ENTH CURVE set point values.
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 econo-
mizing 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.
Figure 62 shows the 5 current boundaries. There is also a high lim-
it 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.
Fig. 62 — Single Enthalpy Curve Boundaries
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
Table 18 — 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
8
0
60
2
8
.0
8
0
36.
8
66.3
8
0.1
ES2
75
57
26.0
75
39.6
63.3
8
0.0
ES3
70
54
24.0
70
42.3
59.7
8
1.4
ES4
65
51
22.0
65
44.
8
55.7
8
4.2
ES5
60
4
8
20.0
60
46.9
51.3
88
.5
HL
8
6
66
32.4
8
6
3
8
.9
72.4
8
0.3
Summary of Contents for Puron R-410A
Page 29: ...29 Fig 44 RTU Open Overlay for Economizer Wiring ...
Page 30: ...30 Fig 45 VFD Overlay for W2770 Controller Wiring ...
Page 50: ...50 Fig 63 50KC Typical Unit Wiring Diagram Power 06A 208 230 3 60 ...
Page 51: ...51 Fig 64 50KC Unit Wiring Diagram Control A06 ...
Page 77: ...77 Fig C Unit Wiring Diagram Power for Sizes A04 and A06 208 230 1 60 ...
Page 78: ...78 Fig D Unit Wiring Diagram Power for Size A05 208 230 1 60 ...
Page 79: ...79 Fig E Unit Wiring Diagram Power for Sizes A04 A06 208 230 3 60 460 3 60 575 3 60 ...
