W7212, W7213, W7214 ECONOMIZER LOGIC MODULES
63-2596—09
8
SETTINGS AND ADJUSTMENTS
CAUTION
Equipment Damage Hazard.
Excessive force can damage potentiometer
controls.
Use a small screwdriver or the plastic tool provided
with the economizer when adjusting all potentiometers
located on the unit.
Potentiometers with screwdriver adjustment slots, located on
device face, provide adjustments for several parameters
(see Fig. 5 for locations on device):
— DCV setpoint.
— Minimum damper position.
— DCV maximum damper position.
— Enthalpy changeover.
— Exhaust setpoint.
Fig. 5. Potentiometer and LED locations (W7212 shown).
Demand Control Ventilation Setpoint
The logic module modulates the outdoor damper to provide
ventilation based on the 2-10 Vdc DCV input (AQ-AQ1
terminals). With no cooling signal, the DCV overrides the
outdoor air damper when ventilation requires additional
outdoor air.
EXAMPLE: CO2 sensor with 2 to 10 Vdc output range 0 to
2000 ppm. Two (2) Vdc is equal to 0 ppm, 10 Vdc is equal to
2000 ppm, threshold is determined to be 1000 ppm. DCV
potentiometer to be set at 6 Vdc.
Adjust the potentiometer with a small screwdriver by turning
the pot to the fully CCW then fully CW positions to determine
the end stops. Set the pot for 6 Vdc in the mid position.
Adjusting Minimum and Maximum
Positions
The minimum position is defined by the minimum outdoor air
flow required in the building during the occupied period. The
MIN POS and DCV MAX position potentiometers allow the
installer to set the proper ventilation based on occupancy
established by ASHRAE standard 62.1. When used with a
CO2 occupancy sensor the minimum position will modulate
between the MIN POS pot setting and the DCV MAX pot
setting based on the CO2 input to the AQ-AQ1 terminals from
the CO2 sensor located in the space. When a CO2 sensor is
NOT USED with the unit, the OA dampers will modulate based
on the actions in Table 1. Setting the DCV maximum position of
the damper prevents the introduction of large amounts of hot or
cold air into the space by preventing the dampers from opening
100% during a call for additional ventilation. On a call for
cooling AND the OA is good for economizing, the unit will
override the DCV MAX setting and allow the dampers to drive
full open.
IMPORTANT
With the DCV maximum position set below the
minimum position, the minimum position overrides the
maximum position with the series 2 units.
NOTES:
—
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 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. Some models
of the W7212 close the damper fully and others
close the damper to minimum position. Check the
label on the box for position of damper on freeze
protection. If the CO2 sensor should fail, the
W7212 defaults to DCV maximum, providing mini-
mum ventilation for the maximum design occu-
pancy.
Minimum Position Adjustment
For detailed assistance in minimum position selection
reference the Economizer Application Guide (form 63-8594)
Ventilation section. The following provides basic guidelines for
minimum position selection and adjustment:
IMPORTANT
• Adjust the minimum position potentiometer to allow
the minimum amount of outdoor air for building efflu-
ents, as required by local codes, to enter the building.
• This procedure requires use of a quality thermometer
capable of reading to 0.5°F [0.25°C].
NOTE: Make ventilation adjustments with at least a 10°F
[6°C] temperature difference between outdoor and
return air.
1.
Calculate the appropriate mixed air temperature, see
Equation 1.
Equation 1 will be used to set the damper positions for
MIN POS and DCV MAX. Without a DCV sensor con-
nected to AQ-AQ1, use the MIN POS pot and this proce-
dure to adjust the damper positions for minimum OA
when the space is occupied. When using a DCV sensor
you will need to set the MIN POS and DCV MAX posi-
tions using this procedure. DCV MAX will be the same as
the MIN POS above (without a DCV sensor) and the MIN
POS will lower than the DCV MAX %.
2.
Disconnect mixed air sensor from terminals T and T1.
3.
Place a jumper across terminals T and T1.
DEMAND CONTROL
VENTILATION SETPOINT
ENTHALPY
CHANGEOVER SETPOINT
LED LIGHTS WHEN
DEMAND CONTROL
VENTILATION INPUT
IS ABOVE SETPOINT
EXHAUST
FAN SETPOINT
LED LIGHTS
WHEN EXHAUST
CONTACT IS MADE
MINIMUM DAMPER
POSITION SETTING
M20604B
N1
P1
T1
N
2V
2V
2V
B
A
SR
SO
AQ
C
D
Free
Cool
10V
EXH
DCV
EXH
Set
10V
DCV
Max
10V
DCV
Set
Min
Pos
Open
P
T
AQ1
SO+
SR+
MAXIMUM DAMPER
DEMAND CONTROL
VENTILATION SETPOINT
LED LIGHTS WHEN
OUTDOOR AIR IS
SUITABLE FOR
FREE COOLING
B
A
D
E
C
W7212C modules have
the "E" enthalpy curve
