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Economizer Controller
Enthalpy Settings
NOTICE
Equipment Damage!
Electrostatic discharge can short equipment circuitry.
Ensure that you are properly grounded before handling
the sensor.
When the outside air temperature, enthalpy, and dew
point are below the respective setpoints, the outdoor air
can be used for economizing. See
Note: The controller calculates the enthalpy and dew
point using the outside air temperature and
humidity input from the outside air sensor.
1. There are 5 boundaries (setpoints ES1 through ES5),
which are defined by dry bulb temperature, enthalpy
and dew point. See
Table 9, p.
2. When conditions are below the selected boundary, the
economizer sets the economizing mode to YES and
economizing is available. When conditions are above
the selected boundary, the conditions are not good to
economize and the mode is set to NO.
Note: When using the enthalpy (Sylk Bus) sensors, there
will be a slight delay while the controller and the
sensor communicate. Analog sensors do not
communicate on the Sylk Bus and output a 20k
ohm signal to the controller with an instantaneous
response time.
Figure 17. Single enthalpy curve and boundaries
Note: When the OA temperature, OA humidity, and the
OA dew point are all below the selected boundary,
the economizer sets the economizing mode to YES
(economizing is available).
20
Figure 17, p. 20
20.
Table 9.
Single enthalpy and dual enthalpy boundaries
(parameters ES1 through ES5)
Temp.
Temp.
dry-
dew
Enth.
Enth.
Bulb
point
(btu/
Curve
(ºF)
(ºF)
lb/da)
ES1
80.0
60.0
28.0
ES2
75.0
57.0
26.0
ES3
70.0
54.0
24.0
ES4
65.0
51.0
22.0
ES5
60.0
48.0
20.0
HL
86.0
66.0
32.4
Note: For differential enthalpy there is a high limit
boundary. The high limit boundary is ES1 when
there are no stages of mechanical cooling
energized and HL when a compressor stage is
energized.
Point P1
Point P2
Temp.
Humid.
Temp.
Humid.
ºF
%RH
ºF
%RH
80.0
36.8
66.3
80.1
75.0
39.6
63.3
80.0
70.0
42.3
59.7
81.4
65.0
44.8
55.7
84.2
60.0
46.9
51.3
88.5
86.0
38.9
72.4
80.3
ACC-SVN203C-EN
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