Bryant 548F - Manual (Page 19)

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10. Remove the indoor fan motor access panel. See
Fig. 29.
11. Mount the supply air temperature sensor to the lower
left portion of the indoor blower housing with the two
(2) screws provided (see Fig. 30). Connect the violet
and pink wires to the corresponding connections on
the supply air temperature sensor. Replace the indoor
fan motor access panel.
CO
2
Control Set Up
If a CO
2
sensor is not being used, proceed to the next section.
If a CO
2
sensor is being used, perform the following:
1. Determine the value at which you want the minimum
position of the dampers to begin opening to allow a
greater amount of outdoor air to enter. The range is
800 to 1,400 ppm.
2. Locate the CO
2
SP (PPM) potentiometer and adjust
to the desired set point. See Fig. 31.
Mechanical Cooling Lockout
Determine the outdoor-air temperature at which you want
the mechanical cooling (compressors) to be disabled. Locate
the mechanical cooling lockout (MECH CLG LOCKOUT)
potentiometer. To disable this feature, turn the potentiome-
ter counterclockwise (CCW) to the OFF position. Otherwise,
set the value between 10 and 60 F. Mechanical cooling will
not operate when the outdoor-air temperature is below this
value. See Fig. 31.
Dry Bulb Changeover Set Up
Determine the dry bulb changeover set point from Table 3.
The settings are A, B, C and D. Locate the ECON SP potenti-
ometer and set the dry bulb changeover set point. See
Fig. 31. When the OAT is above this set point, the damper is
limited to minimum position setting.
Table 3 — Changeover Set Points
*Field-installed accessory.
If a potentiometer fails, its setting will default to the values
in Table 4.
Table 4 — Default Potentiometer Settings
Ventilation Air (Minimum Position Set Up)
If ventilation air is not required, proceed to Step 5. If ventila-
tion air is required, perform the following:
1. The indoor fan must be on to set the ventilation air.
Either put the thermostat in the Continuous Fan
mode or jumper the R and G terminals at the rooftop
unit connection board.
2. Locate the minimum position (MIN POS) potentiome-
ter. Turn the potentiometer full CCW to fully close
the outdoor air dampers. Turn the potentiometer
gradually clockwise (CW) to the desired position. See
Fig. 31.
3. Replace the filter access panel. See Fig. 20. Ensure
the filter access panel slides along the tracks and is
securely engaged.
4. Calculate the minimum airflow across the
EconoMi$er.
a. Calculate % of outside air using the following
formula.
% Outdoor air through EconoMi$er
b. Divide total CFM by percentage outdoor air, this
gives outdoor air volume in CFM.
5. Turn on base unit power.
NOTE: The EconoMi$er begins operation three minutes after
power up.
6. See Fig. 32 for barometric relief damper characteristics.
SETTINGS A B C D
Dry Bulb (°F) 73 69 66 63
Single Enthalpy* (Btu/lb) 27 25 24 22
Differential Temperature*
(°F, Not Adjustable)
2 2 2 2
Differential Enthalpy*
(Btu/lb, Not Adjustable)
1 1 1 1
POTENTIOMETER DEFAULT SETTING
CO
2
SP (PPM) 1,000
MECH CLG LOCKOUT 47°
ECON SP D
MIN POS (%) 20
% Outdoor air =
Mixture Temp – Return Air Temp
Outdoor Temp – Return Air Temp
WARNING: Personal Injury Hazard. Avoid pos-
sible injury by keeping fingers away from damper
blades.
CONTROL BOX
ACCESS PANEL
INDOOR FAN MOTOR
ACCESS PANEL
SUPPLY AIR
TEMPERATURE
SENSOR
MOUNTING
LOCATION
SUPPLY AIR
TEMPERATURE
SENSOR
Fig. 29 — Typical Access Panel Locations
(Standard Efficiency Unit Shown)
Fig. 30 — Supply Air Sensor Placement
Fig. 31 — EconoMi$er Control Adjustment
Potentiometers (Factory Settings)