Operation: W7212 - Honeywell C7150B Product Data

OPERATION: W7212

The purpose of the economizer is to use outdoor air for
cooling, whenever possible, to reduce compressor operation.
Power at the N terminal determines the Occupied/Unoccupied
setting:
— W7212:
• 24 Vac (Occupied).
• No power (Unoccupied).
— W7213,W7214:
• W7213 (CHANGEOVER TERMINAL B)
— 24V power to B: System is in heating mode.
— No power to B: System is in cooling mode.
• W7214 (CHANGEOVER TERMINAL O)
— 24V power to O: System is in cooling mode.
— No power to O: System is in heating mode.
NOTE: When module is operating in Occupied mode, the
minimum position is defined by the potentiometer.
When the module is operating in Unoccupied mode,
and there is no call for cooling, the damper drives fully
closed.
When wired as shown in Fig. 28–33, the logic module
responds to the cooling thermostat signal. The system uses
C7400 Solid State Enthalpy Changeover Sensor(s) or C7650
Demand Control
Ventilation (DCV) Outdoor
Below set (DCV High (Free
LED Off) Cooling LED Off)
Low (Free
Cooling LED On)
Above set (DCV High (Free
LED On) Cooling LED Off)
Low (Free
Cooling LED On)
a
For single enthalpy control, the module compares outdoor enthalpy to the ABCD setpoint.
b
Power at N terminal determines Occupied/Unoccupied setting:
• W7212: 24 Vac (Occupied), no power (Unoccupied).
• W7213,W7214: No power (Occupied), 24 Vac (Unoccupied).
c
Modulation is based on the mixed air sensor signal.
d
Modulation is based on the DCV signal.
e
Modulation is based on the greater of DCV and mixed air sensor signals, between minimum position and either maximum posi-
tion (DCV) or fully open (mixed air signal).
f
Modulation is based on the greater of DCV and mixed air sensor signals, between closed and either maximum position (DCV) or
fully open (mixed air signal).
Table 5. W7212 Economizer I/O Logic.
INPUTS
a
Enthalpy
Return Y1
Low On
On
Off
High On
On
Off
Low On
On
Off
High On
On
Off
Dry Bulb Temperature Sensor(s). The C7400 responds to both
dry bulb temperature and humidity, allowing use of outdoor air
at higher temperatures for free cooling when humidity is low.
The C7650 responds only to dry bulb temperature; use only in
dry, arid climates.
The logic module functions as a true first stage of cooling
providing maximum energy economy during the cooling cycle.
It automatically locks out free cooling during heating; holding
the outdoor air damper at the minimum position setting.
The logic module can operate as either a basic free cooling
controller, or it can incorporate additional functions. Table 5
details the input/output (I/O) logic of the module.
S963B1128 REMOTE
POTENTIOMETER
R
CW
CLOSE
W
Fig. 24. S963B1128 Remote Potentiometer used with logic
module for remote damper control.
Compressor
Y2 Stage 1 Stage 2
On On On Minimum position
Off On Off
Off Off Off
On On Off
Modulating
min. position and full-
Off Off Off
open)
Off Off Off Minimum position
On On On
Modulating
min. position and DCV
Off On Off
maximum)
Off Off Off
On On Off
Modulating
Off Off Off
Off Off Off
17
SOLID STATE ECONOMIZER SYSTEM
MINIMUM
POSITION
P1
ADJUSTMENT
P
B
CW
ECONOMIZER
OUTPUTS
b
N Terminal
b
Occupied Unoccupied
Damper
Closed
c
(between Modulating
closed and full-open)
Closed
d
(between Modulating
closed and DCV
maximum)
e
Modulating
M20603A
b
c
(between
d
(between
f
63-2484—2