Bryant DURAPAC 579F Installation, Start-Up And Service Instructions Manual page 19

Adjust the minimum position potentiometer to allow the
minimum 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 out-
door 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 x ) + (TR 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 .10) + (75 x .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 terminals P and P1. If remote damper posi-
tioning is being used, make sure that the terminals
are wired according to Fig. 26 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$erIV damper is desirable when
requiring additional temporary ventilation. If a field-supplied
remote potentiometer (Honeywell part number S963B1128) is
wired to the EconoMi$erIV 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$erIV controller. Wire the field-supplied potenti-
ometer to the P and P1 terminals on the EconoMi$erIV con-
troller. See Fig. 31.
Damper Movement
Damper movement from full open to full closed (or vice
versa) takes 2 1 / minutes.
2
Thermostats
The EconoMi$erIV control works with conventional thermo-
stats that have a Y1 (cool stage 1), Y2 (cool stage 2), W1
(heat stage 1), W2 (heat stage 2), and G (fan). The
EconoMi$erIV control does not support space temperature
sensors. Connections are made at the thermostat terminal
connection board located in the main control box.
Occupancy Control
The factory default configuration for the EconoMi$erIV con-
trol is occupied mode. Occupied status is provided by the
black jumper from terminal TB2-9 to terminal TB2-10.
When unoccupied mode is desired, install a field-supplied
timeclock function in place of the jumper between terminals
TB2-9 and TB2-10. See Fig. 26. When the timeclock contacts
are closed, the EconoMi$erIV control will be in occupied
RA
) = T
M
100
mode. When the timeclock contacts are open (removing the
24-v signal from terminal N), the EconoMi$erIV will be in
unoccupied mode.
Demand Controlled Ventilation (DCV)
When using the EconoMi$erIV for demand controlled venti-
lation, 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
maximum 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 CO
CO set point has not been reached. By the time the CO
2
level reaches the set point, the damper will 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
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.
OA
(T x ) + (TR 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 mini-
mum damper position potentiometer to the correct position.
CO SENSOR MAX RANGE SETTING
2
6000
5000
4000
3000
2000
1000
0
2 3
DAMPER VOLTAGE FOR MAX VENTILATION RATE
Fig. 32 — CO
2
— 19 —
level increases even though the
2
sensor control the economizer damper
2
RA
) = T
M
100
4 5 6 7
Sensor Maximum Range Setting
2
800 ppm
900 ppm
1000 ppm
1100 ppm
8