13
Installing Optional HH57AC081 Single Outside
Air Enthalpy Sensor
When using the HH57AC081 (Honeywell C7400S) enthalpy
sensor (see Fig. 29 and 30) for outside air changeover, the
existing HH79AH001 (Honeywell C7250) dry bulb sensor must
be removed. The enthalpy sensor will be mounted in the same
location as the dry bulb sensor. (See Fig. 1.) When the enthalpy
sensor’s OA temperature, enthalpy, and dew point are below the
respective setpoints, the outside air can be used for free-cooling.
When any of these is above the setpoint, free-cooling will not be
available. Figure 29 shows the enthalpy boundaries in the
W7220 controller. There are 5 enthalpy boundaries (setpoints
ES1 through ES5), which are defined by dry bulb temperature,
enthalpy, and dew point. ES3 is the default setting. Table 7
shows the High Limit Curves for each setting.
The 2 gray wires with a plug from the EconoMi$er X harness in
the return chamber plug directly into the HH57AC081 enthalpy
sensor. See Fig. 23 and 28 for wiring.
Fig. 29 — Enthalpy Curve Boundaries
Fig. 30 — HH57AC081 Dimensional, Connection and
Switching Information
LEGEND
Default Setting = OFF-OFF-OFF
IMPORTANT: To use the HH57AC081 sensor for outside air
sensor, the dip switches on the sensor must be set to
OFF-OFF-OFF. (See Table 8.)
ECONOMIZING
AVAILABLE
NOT AVAILABLE
ENTHALPY
RA HUM (%RH)
RA TEMP
TEMPERATURE
ABSOLUTE HUMIDITY
ES5
ES4
ES3
ES2 ES1
HL
P1
(T,RH)
P2 (T,RH)
SINGLE ENTHALPY
DUAL ENTHALPY
HIGH LIMIT
Table 7 — Single Enthalpy and Dual Enthalpy High Limit Curves
ENTHALPY
CURVE
TEMP. DRY
BULB (F)
TEMP.
DEWPOINT (F)
ENTHALPY
(btu/lb/da)
POINT P1 POINT P2
TEMP. (F)
HUMIDITY
(%RH)
TEMP. (F)
HUMIDITY
(%RH)
ES1 80 60 28.0 80 36.8 66.3 80.1
ES2 75 57 26.0 75 39.6 63.3 80.0
ES3 70 54 24.0 70 42.3 59.7 81.4
ES4 65 51 22.0 65 44.8 55.7 84.2
ES5 60 48 20.0 60 46.9 51.3 88.5
HL 86 66 32.4 86 38.9 72.4 80.3
DA
RA
OA
123
S-Bus
Temp & Humidity
HH57AC081
51/64 (21)
4-1/4 (108)
2-3/4 (70)
2-1/64 (55)
S-Bus
NOTE: Dimensions are in inches (mm)
Table 8 — HH57AC081 Sensor Dip Switch Settings
USE
DIP SWITCH POSITIONS FOR SWITCHES 1, 2, AND 3
1 2 3
DA OFF ON OFF
RA ON OFF OFF
OA OFF OFF OFF
DA — Discharge Air (not used on EconoMi$er X)
OA — Outside Air
RA — Return Air
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