Section 9 - W7212, W7213 and W7214 Economizer Modules
85 Honeywell Economizers 63-8594-02
When the mixed air sensor takes control
based on an increased requirement for
cooling, it overrides the DCV maximum
position potentiometer and can drive the
damper full-open.
If the mixed air temperature drops to 45°F, the
mixed air sensor overrides the DCV and fully
closes the damper to protect from freezing the
hot or chilled water coils. Control returns to
normal once the mixed air temperature rises to
48°F.
DCV setpoint is the same as the W7215. The
setpoint is based on the output of the CO
2
sensor (e.g., 0-10 Vdc output for CO
2
ppm of
500-1500 ppm where 0 Vdc = 500 ppm and 10
Vdc = 1500 ppm. If setpoint is 1000 ppm or 6
Vdc, then the OA damper will begin to module
open when output from CO
2
sensor is 6 Vdc).
DCV LED light will illuminate when CO
2
level
is above setpoint.
Using Multiple CO2 sensors on
the AQ-AQ1 terminals for zones
You can add up to five (5) CO
2
sensors from
different spaces to the W7212 economizer.
The CO
2
sensor with the highest call will take
precedence and the outdoor dampers will
drive open based on the highest CO
2
sensor
output OR the call for free cooling for the
economizer. The other four (4) remaining
spaces will be ventilated to the same level
unless there is a mechanical ventilation limit in
the system. There must be one schottky diode
(BAT43 or IN5819) in series with the + from
the sensor to the + (AQ) terminal on the
W7212. Each sensor must have the diode in
series. Each C7232 sensor puts out about 0.2
volts more than is put on the AQ+ line due to
the inherent 0.2 volt drop across each diode.
The AQ+ line will be 0.2 V lower than the
highest C7232 output. When that output
crosses the threshold set on the DCV set pot,
the motor will drive towards open. You need to
be aware that the AQ+ line will never reach 10
V but will max at near 9.8 V due to the diodes.
Free cool LED illuminates when outdoor air is
suitable for free cooling whether Y1 from the
commercial thermostat is calling for cooling or
not.
The W7212 uses the electronic A, B, C, D and
high enthalpy curves on the psychrometric
chart.
Minimum Position Adjustment
The following provides basic guidelines for
minimum position selection and adjustment:
IMPORTANT
Adjust the minimum position potentiom-
eter to allow the minimum amount of
outdoor air for building effluents, as
required by local codes, to enter the
building. This procedure requires use of
a quality thermometer capable of read-
ing to 0.5°F (0.25°C).
NOTE: Make minimum position adjustments
with at least a 10°F (-12°C)
temperature difference between
outdoor and return air.
1. Calculate the appropriate mixed air
temperature, see the Equation below.
2. Disconnect mixed air sensor from
terminals T and T1.
3. Place a jumper across terminals T and
T1.
4. Ensure that either the factory-installed
jumper is in place across terminals P and
P1 or, if remote damper position is
required, that it is wired according to the
image below, turned fully clockwise.
S963B1128 Remote Potentiometer used with
logic module for remote damper control
M20603A
P1
P
ECONOMIZER
R
MINIMUM
POSITION
ADJUSTMENT
W
B
CW
CLOSE
S963B1128 REMOTE
POTENTIOMETER
CW
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