Bryant 548F - Manual (Page 38)

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Check cooling effects at a setting below room temperature.
Check unit charge. Refer to Refrigerant Charge section on
page 40. Unit must operate for at least 15 minutes before
adjusting charge.
Reset thermostat at a position above room temperature.
Compressor will shut off.
A. To Shut Off Unit
Set system selector switch at OFF position. Resetting ther-
mostat at a position above room temperature shuts unit off
temporarily until space temperature exceeds thermostat
setting.
X. HEATING
To start unit, turn on main power supply.
Set system selector switch at HEAT position, and set ther-
mostat at a setting above room temperature. Set fan at
AUTO position.
First stage of thermostat energizes the indoor fan, compres-
sor, and outdoor fan; second stage energizes electric heater
elements, if installed. Check heating effects at air supply
grille(s).
If electric heaters do not energize, reset limit switch (located
on indoor-fan scroll) by depressing button located between
terminals on the switch.
A. To Shut Off Unit
Set system selector switch at OFF position. Resetting ther-
mostat at a position below room temperature temporarily
shuts unit off until space temperature falls below thermostat
setting.
XI. SAFETY RELIEF
A soft solder joint at the suction line fitting provides
pressure relief under abnormal temperature and pressure
conditions.
XII. VENTILATION (CONTINUOUS FAN)
Set fan and system selector switches at ON and OFF posi-
tions, respectively. Indoor fan operates continuously to pro-
vide constant air circulation.
XIII. OPERATING SEQUENCE
A. Cooling, Units Without Economizer
When thermostat calls for cooling, terminals G and Y1 are
energized. The indoor fan contactor (IFC), compressor con-
tactor (C1), reversing valve solenoid (RVS), indoor-fan motor,
compressor, and outdoor fan start. The outdoor-fan motor
runs continuously while unit is cooling.
B. Heating, Units Without Economizer
Upon a call for heating through terminal W1, IFC, compres-
sor, and outdoor fan are energized. On units equipped for 2
stages of heat, when additional heat is needed HC is ener-
gized through W2.
C. Cooling Units With EconoMi$er
When the OAT is above the ECON SP set point and the room
thermostat calls for Stage 1 cooling (R to G + Y1), the indoor-
fan motor (IFM) is energized and the EconoMi$er damper
modulates to minimum position. The compressor contactor is
energized to start the compressor and outdoor-fan motor
(OFM). After the thermostat is satisfied, the damper modu-
lates to the fully closed position when the IFM is deenergized.
When the OAT is below the ECON SP setting and the room
thermostat calls for Stage 1 cooling (R to G + Y1), the
EconoMi$er modulates to the minimum position when the
IFM is energized. The EconoMi$er provides Stage 1 of
cooling by modulating the return and outdoor air dampers to
maintain a 55 F supply air set point. If the supply-air tem-
perature (SAT) is greater than 57 F, the EconoMi$er modu-
lates open, allowing a greater amount of outdoor air to enter
the unit. If the SAT drops below 53 F, the outdoor air damper
modulates closed to reduce the amount of outdoor air. When
the SAT is between 53 and 57 F, the EconoMi$er maintains
its position.
If outdoor air alone cannot satisfy the cooling require-
ments of the conditioned space, and the OAT is above the
MECH CLG LOCKOUT set point, the EconoMi$er inte-
grates free cooling with mechanical cooling. This is accom-
plished by the strategies below.
NOTE: Compressor has a two-minute Minimum On, Mini-
mum Off, and interstage delay timer.
1. If Y1 is energized, and the room thermostat calls for
Y2 (2-stage thermostat), the compressor and OFM
are energized. The position of the EconoMi$er
damper is maintained at its current value.
2. If Y1 is energized for more than 20 minutes, and Y2 is
not energized (whether or not a 2-stage thermostat is
used), the compressor and OFM are energized. The
position of the EconoMi$er damper is maintained at
its current value.
3. If Y1 is energized, and the compressor no. 1 is already
energized (see Step 2) and the room thermostat calls
for Y2, compressor no. 1 continues to operate.
4. If compressor no. 1 is energized and the thermostat is
satisfied, the compressor no. 1, the OFM, and IFM
are deenergized and the EconoMi$er modulates
closed.
When the OAT is below the MECH CLG LOCKOUT set
point, the compressors remain off.
D. Cooling, Units With Durablade Economizer
When the outdoor-air temperature is above the outdoor-air
thermostat (OAT) setting and the room thermostat calls for
cooling, compressor contactor is energized to start compres-
sor and the outdoor-fan motor (OFM). The indoor-fan motor
(IFM) is energized and the economizer damper moves to the
minimum position. After the thermostat is satisfied, the
indoor fan turns off. The damper then moves to the fully
closed position. When using continuous fan, the damper
moves to the minimum position.
When the outdoor-air temperature is below the OAT setting
and the thermostat calls for cooling, the economizer damper
moves to the minimum position. If the supply-air tempera-
ture is above 57 F, the damper continues to open until it
reaches the fully open position or until the supply-air tem-
perature drops below 52 F.
When the supply-air temperature falls between 57 F and
52 F, the damper will remain at an intermediate open posi-
tion. If the supply-air temperature falls below 52 F, the
damper will modulate closed until it reaches the minimum
position or until the supply-air temperature is above 52 F.
When the thermostat is satisfied, the damper moves to the
fully closed position when using AUTO. fan or to the mini-
mum position when using continuous fan.
If the outdoor air alone cannot satisfy the cooling requirements
of the conditioned space, economizer cooling is integrated with
mechanical cooling, providing 2 stages of cooling. Compressor
and the outdoor fan will be energized and the position of the
economizer damper will be determined by the supply-air tem-
perature. When the second stage of cooling is satisfied, the
compressor and OFM will be deenergized. The damper posi-
tion will be determined by the supply-air temperature. When