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2SP
H/C
(2
SPEED
OPERATION
FAN TYPE = 2SP H/C is not used on RHV090-120 units
3 SPEED FAN OPERATION
FAN TYPE = 3SPEED is not used on RHV090-120 units
ENTHALPY SETTINGS
When the OA temperature, enthalpy and dew point are be-
low the respective set points, the Outdoor Air can be used
for economizing. Figure 46 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.
Economizing
Available
Not Available
Temperature
ENTHALPY
TEMP. DRY
CURVE
BULB (
°
ES1
80
ES2
75
ES3
70
ES4
65
ES5
60
HL
86
38
HEAT/COOL)
SPEED
Fig. 46 — Single Enthalpy Curve Boundaries
Table 13 — Single Enthalpy and Dual Enthalpy High Limit Curves
TEMP.
ENTHALPY
F)
DEWPOINT (
F)
(btu/lb/da)
°
60
57
54
51
48
66
Specifications subject to change without notice.
FAN
Refer to Table 13 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 econo-
mizer 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.
Figure 46 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 13 provides the values for each boundary limit.
POINT P1
TEMP. (
F)
°
28.0
80
26.0
75
24.0
70
22.0
65
20.0
60
32.4
86
Dual Enthalpy
High Limit
Single Enthalpy
P2 (T,RH)
P1
(T,RH)
ES4
ES2
ES5
ES3
POINT P2
HUMIDITY
TEMP. (
F)
°
(%RH)
36.8
66.3
39.6
63.3
42.3
59.7
44.8
55.7
46.9
51.3
38.9
72.4
RHV-090-120-01SI
ES1
HL
HUMIDITY
(%RH)
80.1
80.0
81.4
84.2
88.5
80.3
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