Economizer Controller
20 ACC-SVN203C-EN
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
po
int are be
low the respective setpoints, the outdoor air
can be used for economizing. See Figure 17, p. 20
Note: The controller calculates the enthalpy and dew
po
int using the outside air temperature and
humidity input from the outside air sensor.
1. There are 5 boundaries (setpoints ES1 through ES5),
which are
de
fined by dry bulb temperature, enthalpy
and dew point. See Table 9, p. 20.
2. When conditions are below the selected boundary, the
e
conom
izer 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
wi
ll 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.
Table 9. Single enthalpy and dual enthalpy boundaries
(parameters ES1 through ES5)
Enth.
Curve
Temp.
dry-
Bulb
(ºF)
Temp.
dew
point
(ºF)
Enth.
(btu/
lb/da)
Point P1 Point P2
Temp.
ºF
Humid.
%RH
Temp.
ºF
Humid.
%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
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.
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).
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