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The unoccupied minimum position can only be set at the con-
troller. The occupied minimum position set point configured
at the EconoMi$er+ controller should be set to 0 when using
a remote potentiometer. The occupied minimum position will
also be used as part of the IAQ routing; it will be the
maximum position the damper moves to when there is an
IAQ call.
If the remote potentiometer (occupied) position is greater
than the EconoMi$er+ controller unoccupied minimum posi-
tion, then the remote potentiometer setting will be used. The
remote potentiometer is field supplied and must be a 3-wire,
linear potentiometer with a resistance between 10K ohm
and 100K ohm (such as the Honeywell S963B1128).
Q.Demand Ventilation Control
Demand ventilation control uses an IAQ sensor
(CRE+PLUG001A00 required) to control the amount of out-
side air admitted into the system. Normally, the minimum
position of the EconoMi$er+ damper is established based on
the demand occupancy of the space. The IAQ sensor will be
used to modulate the EconoMi$er+ minimum damper posi-
tion below the normal minimum position based on full occu-
pancy. The lower limit is called the base ventilation rate. See
Fig. 32.
If there is no IAQ signal the damper will be in the unoccu-
pied minimum position (configuration item number 3). If
there is an IAQ signal the damper will be in the occupied
minimum position (configuration item number 15), unless
the remote potentiometer is used to override it.
For the demand ventilation control logic, the user configures
the lower and upper actuator position to establish the base
ventilation rate (IAQMIN_SP) and the design ventilation rate
(ECONOMIN_SP) for full occupancy. When the EconoMi$er+
damper is being modulated for demand ventilation control,
the damper position will be between IAQMIN_SP and
ECONOMIN_SP. The upper IAQ differential set point is
DAQHI. The lower IAQ differential set point is DAQLO.
The differential set points represent the differential CO
2
level (in ppm) above the outdoor reference IAQ levels. Nor-
mally, the outdoor reference IAQ levels are around 400 ppm,
but the value should be configured based on the reference
levels taken at the job site.
The following equation is used to determine EconoMi$er+
damper position (ECONOMIN_POS):
R. CO
2
Sensor Configuration
The CO
2
sensor has preset standard voltage settings that
can be selected anytime after the sensor is powered up. See
Table 7.
1. Press Clear and Mode buttons. Hold at least 5 seconds
until the sensor enters the Edit mode.
2. Press Mode 2 times. The STDSET Menu will appear.
3. Use the Up/Down button to select the preset number.
See Table 7.
4. Press Enter to lock in the selection.
Press Mode to exit and resume normal operation. The cus-
tom settings of the CO
2
sensor can be changed any time after
the sensor is energized. Follow the steps below to change the
non-standard settings:
1. Press Clear and Mode buttons. Hold at least 5 sec-
onds until the sensor enters the Edit mode.
2. Press Mode twice. The STDSET Menu will appear.
3. Use the Up/Down button to toggle to the NONSTD
menu and press Enter.
4. Use the Up/Down button to toggle through each of
the nine variables, starting with Altitude, until the
desired setting is reached.
5. Press Mode to move through the variables.
6. Press Enter to lock in the selection, then press Mode
to continue to the next variable.
S. Dehumidification of Fresh Air with Demand Control
Ventilation (DCV)
Information from ASHRAE (American Society of Heating,
Refrigeration and Air Conditioning Engineers) indicates that
the largest humidity load on any zone is the fresh air intro-
duced. For some applications, a device such as a energy
recovery unit is added to reduce the moisture content of the
fresh air being brought into the building when the enthalpy
is high. In most cases, the normal heating and cooling pro-
cesses are more than adequate to remove the humidity loads
for most commercial applications.
This makes the control of the dehumidification device simple
when using the enthalpy or differential enthalpy sensor. The
enthalpy sensor or differential enthalpy sensor is installed
on the equipment to determine economizer operation. The
high enthalpy signal from the temperature and humidity
sensors or differential temperature and humidity sensors
can be used to turn on the outdoor air moisture removal
device any time fresh air is required for the space.
The energy recovery device should be sized for maximum
latent and sensible conditioning at maximum ventilation on
a design day.
A calculation for leaving-air temperature on a low ambient,
low ventilation day should also be done to determine the
supply-air temperature of the return and pre-conditioned
outside air. The design should produce air temperature
somewhat near room conditions to prevent reheat of the air
mixture. The energy recovery device should be interlocked
with the heat to turn off the device when in the heat mode.
IAQMIN_SP + =
(ECONOMIN_SP – IAQMIN_SP) * (IAQ –OAQ –DAQLO)
(DAQHI – DAQLO)
100
500
700
1100
INSIDE/OUTSIDE CO
2
DIFFERENTIAL
INSIDE CO
2
CONCENTRATION
AQ
DIFFERENTIAL
LOW (DAQLO)
AQ
DIFFERENTIAL
HIGH (DAQHI)
IAQ
MINIMUM
ECONOMIZER
POSITION
SET POINT
(IAQMIN_SP)
ECONOMIZER
MINIMUM
OCCUPIED
DAMPER
POSITION
(ECONOMIN_SP)
VENTILATION FOR PEOPLE
VENTILATION FOR SOURCES
FULL OCCUPANCY
VENTILATION RATE
DAMPER
POSTION
CO LEVEL
2
OUTDOOR REFERENCE
LEVEL (OAQ)= 400
Fig. 32 — Demand Ventilation Control