Carrier 48FC 08-16 Series Service And Maintenance Instructions page 55

Exhaust Set Point Adjustment
The exhaust set point will determine when the exhaust fan runs
based on damper position (if accessory power exhaust is in-
stalled). The set point is modified with the Exhaust Fan set point
(EXH SET) potentiometer. See Fig. 78. The set point represents
the damper position above which the exhaust fans will be turned
on. When there is a call for exhaust, the EconoMi$er IV controller
provides a 45 ± 15 second delay before exhaust fan activation to
allow the dampers to open. This delay allows the damper to reach
the appropriate position to avoid unnecessary fan overload.
Minimum Position Control
There is a minimum damper position potentiometer on the
EconoMi$er IV controller. See Fig. 78. The minimum damper po-
sition maintains the minimum airflow into the building during the
occupied period.
When using demand controlled ventilation, the minimum damp-
er position represents the minimum ventilation position for Vola-
tile Organic Compound (VOC) ventilation requirements. The
maximum demand ventilation position is used for fully occupied
ventilation.
When demand controlled ventilation is not being used, the mini-
mum position potentiometer should be used to set the occupied
ventilation position. The maximum demand ventilation position
should be turned fully clockwise.
Adjust the minimum position potentiometer to allow the mini-
mum amount of outdoor air, as required by local codes, to enter
the building. Make minimum position adjustments with at least
10°F temperature difference between the outdoor and return-air
temperatures.
To determine the minimum position setting, perform the following
procedure:
1. Calculate the appropriate mixed air temperature using the
following formula:
OA
(T ) + (T
x
O
100
T = Outdoor-Air Temperature
O
OA= Percent of Outdoor Air
T = Return-Air Temperature
R
RA= Percent of Return Air
T = Mixed-Air Temperature
M
As an example, if local codes require 10% outdoor air during
occupied conditions, outdoor-air temperature is 60°F, and
return-air temperature is 75°F.
(60 x 0.10) + (75 x 0.90) = 73.5°F
2. Disconnect the supply air sensor from terminals T and T1.
3. Ensure that the factory-installed jumper is in place across ter-
minals P and P1. If remote damper positioning is being used,
make sure that the terminals are wired according to Fig. 72
and that the minimum position potentiometer is turned fully
clockwise.
4. Connect 24 vac across terminals TR and TR1.
5. Carefully adjust the minimum position potentiometer until
the measured mixed air temperature matches the calculated
value.
6. Reconnect the supply air sensor to terminals T and T1.
Remote control of the EconoMi$er IV damper is desirable when
requiring additional temporary ventilation. If a field-supplied re-
mote potentiometer (Honeywell P/N: S963B1128) is wired to the
EconoMi$er IV controller, the minimum position of the damper
can be controlled from a remote location.
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. 78.)
RA
) = T
x
M
R 100
Damper Movement
Damper movement from full open to full closed (or vice versa)
takes 2-1/2 minutes.
Thermostats
The EconoMi$er ® IV control works with conventional thermo-
stats that have a Y1 (cool stage 1), Y2 (cool stage 2), W1 (heat
stage 1), W2 (heat stage 2), and G (fan). The EconoMi$er
control does not support space temperature sensors. Connec-
tions are made at the thermostat terminal connection board lo-
cated in the main control box.
Occupancy Control
The factory default configuration for the EconoMi$er IV con-
trol is occupied mode. Occupied status is provided by the black
jumper from terminal TR to terminal N. When unoccupied
mode is desired, install a field-supplied timeclock function in
place of the jumper between TR and N. When the timeclock
contacts are closed, the EconoMi$er IV control will be in occu-
pied mode. When the timeclock contacts are open (removing
the 24-v signal from terminal N), the EconoMi$er IV will be in
unoccupied mode.
Demand Controlled Ventilation (DCV)
When using the EconoMi$er IV for demand controlled ventila-
tion, there are some equipment selection criteria which should
be considered. When selecting the heat capacity and cool ca-
pacity of the equipment, the maximum ventilation rate must be
evaluated for design conditions. The maximum damper posi-
tion 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 occupan-
cy, 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 maximum ven-
tilation 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 CO
increases even though the CO
By the time the CO level reaches the set point, the damper will
2
be at maximum ventilation and should maintain the set point.
In order to have the CO
in this manner, first determine the damper voltage output for
minimum or base ventilation. Base ventilation is the ventila-
tion required to remove contaminants during unoccupied peri-
ods. The following equation may be used to determine the per-
cent 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.
OA
(T
x
O
100
T = Outdoor-Air Temperature
O
OA= Percent of Outdoor Air
T = Return-Air Temperature
R
RA= Percent of Return Air
T = Mixed-Air Temperature
M
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 maximum ventilation rate
of 20% (or base plus 15 cfm per person). Use Fig. 80 to deter-
mine the maximum setting of the CO
1100 ppm set point relates to a 15 cfm per person design. Use the
1100 ppm curve on Fig. 80 to find the point when the CO
55
set point has not been reached.
2
sensor control the economizer damper
2
RA
) + (T ) = T
x
M
100
R
sensor. For example, an
2
® IV
level
2
sensor
2