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To control the minimum damper position remotely, remove the
factory-installed
jumper
on the P and P1 terminals
on the
EconoMi$er IV controller. Wire the field-supplied
potentiometer
to the P and P1 terminals on the EconoMi$er IV controller. (See
Fig. 22.)
Damper Movement
When the EconoMi$er IV board receives initial power, it can take
the damper up to 21/2 minutes before it begins to position itself.
After the initial positioning,
subsequent
changes
to damper
position will take up to 30 seconds to initiate. Damper movement
from full open to full closed (or vice versa) takes 21/2 minutes.
Thermostats
The EconoMi$er IV control works with conventional thermostats
that have a Y1 (cool stage 1), Y2 (cool stage 2), Wl (heat stage 1),
W2 (heat stage 2), and G (fan). The EconoMi$er IV control does
not support
space temperature
sensors
like the T55 or T56.
Connections are made at the thermostat terminal connection board
located in the main control box.
Demand Control Ventilation
When using the EconoMi$er IV for demand control ventilation,
there are some equipment
selection
criteria which should
be
considered. When selecting the heat capacity and cool capacity of
the equipment, the maximum ventilation rate must be evaluated for
design
conditions.
The
maximum
damper
position
must
be
calculated to provide the desired fresh air.
Typically the maximum ventilation rate will be about 5 to 10%
more than the typical cfm required per person,
using normal
outside air design criteria.
A proportional
anticipatory
strategy should be taken with the
following
conditions:
a
zone
with
a
large
area,
varied
occupancy,
and equipment
that cannot
exceed
the required
ventilation
rate at design conditions.
Exceeding
the required
ventilation
rate means the equipment
can condition
air at a
naaxinmm ventilation
rate that is greater
than the required
ventilation
rate for
maximum
occupancy.
A
proportional-
anticipatory
strategy
will
cause
the fresh
air supplied
to
increase as the room CO2 level increases even though the CO2 set
point has not been reached. By the time the CO2 level reaches the
set point, the damper will be at maximum ventilation and should
maintain the set point.
In order to have the CO2 sensor control the economizer damper in
this manner,
first determine
the damper
voltage
output
for
minimum or base ventilation. Base ventilation is the ventilation
required to remove contaminants during unoccupied periods. The
following
equation
may be used to determine
the percent of
outside-air entering the building for a given damper position. For
best results there should be at least a 10 degree difference in outside
and return-air temperatures.
(To x OA) + (TR x RA) = TM
TO = Outdoor-Air Temperature
OA = Percent of Outdoor Air
TR = Return-Air Temperature
RA = Percent of Return Air
TM = Mixed-Air Temperature
Once base ventilation
has been determined,
set the minimum
damper position potentiometer to the correct position.
The
same
equation
can be
used
to determine
the
occupied
or
maximum
ventilation
rate
to
the
building.
For
example,
an
output
of 3.6 volts
to the actuator
provides
a base ventilation
rate
of 5% and an output of 6.7 volts provides
the n_axinmm
ventilation
rate
of 20% (or base
plus 15 cfm per person).
Use Fig.
25 to
determine
the n_axinmm
setting of the CO2 sensor.
For example,
a
1100 ppm set point relates to a 15 cfm per person
design.
Use the
1100 ppm curve on Fig. 25 to find the point when
the CO2 sensor
output will be 6.7 volts. Line up the point on the graph with the left
side of the chart to determine
that the range configuration
for the
CO2 sensor
should
be 1800
ppm. The EconoMi$er
IV controller
will output the
6.7 volts from the CO2 sensor to the actuator
when
the CO2 concentration
in the space is at 1100 ppm.
The DCV set
point
may be left at 2 volts
since the CO2 sensor voltage
will be
ignored
by the EconoMi$er
IV controller
until it rises above the
3.6 volt setting of the n_ininmm
position
potentiometer.
Once the fully occupied
damper
position
has been determined,
set
the n_axinmm
damper
demand
control
ventilation
potentiometer
to
this position.
Do not set to the n_axinmm
position
as this can result
in over-ventilation
to the space and potential
high-humidity
levels.
CO2 Sensor
Configuration
The ('02
sensor
has preset
standard
voltage
settings
that can be
selected
anytime
after the sensor is powered
up. (See Table 8.)
Use setting 1 or 2 for Carrier equipment.
(See Table 8.)
1. Press Clear and Mode buttons.
Hold at least 5 seconds
until
the sensor enters the Edit mode.
2. Press Mode twice. The STDSET
Menu will appear.
3. Use the Up/Down
button
to select the preset number.
(See
Table 80
4. Press Enter to lock in the selection.
5. Press Mode to exit and resume
normal
operation.
The custom
settings
of the CO2 sensor
can be changed
anytime
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 seconds
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.
Dehumidification
of Fresh Air with DCV Control
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 introduced.
For
some applications,
a device such as a 62AQ
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
processes
are more
than adequate
to
remove
the humidity
loads for most commercial
applications.
32
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