Carrier 48TCA04---A12 - Manual (Page 67)

67
direction. To determine whether or not compressor is
rotating in the proper direction:
1. Connect service gauges to suction and discharge pres-
sure fittings.
2. Energize the compressor.
3. The suction pressure should drop and the discharge
pressure should rise, as is normal on any start--up.
If the suction pressure does not drop and the discharge
pressure does not rise to normal levels:
4. Note that the evaporator fan is probably also rotating
in the wrong direction.
5. Turn off power to the unit and install lockout tag.
6. Reverse any two of the unit power leads.
7. Re--energize to the compressor. Check pressures.
The suction and discharge pressure levels should now
move to their normal start--up levels.
NOTE: When the compressor is rotating in the wrong
direction, the unit will make an elevated level of noise
and will not provide cooling.
Cooling
Set space thermostat to OFF position. To start unit, turn on
main power supply. Set system selector switch at COOL
position and fan switch at AUTO. position. Adjust
thermostat to a setting below room temperature.
Compressor starts on closure of contactor.
Check unit charge. Refer to Refrigerant Charge section.
Reset thermostat at a position above room temperature.
Compressor will shut off. Evaporator fan will shut off
after a 30--second delay.
To shut off unit, set system selector switch at OFF
position. Resetting thermostat at a position above room
temperature shuts unit off temporarily until space
temperature exceeds thermostat setting.
Main Burners
Main burners are factory set and should require no
adjustment.
To check ignition of main burners and heating controls,
move thermostat setpoint above room temperature and
verify that the burners light and evaporator fan is
energized. Check heating effect, then lower the thermostat
setting below the room temperature and verify that the
burners and evaporator fan turn off.
Refer to Tables 11 and 12 for the correct orifice to use at
high altitudes.
Heating
1. Purge gas supply line of air by opening union ahead
of the gas valve. If gas odor is detected, tighten union
and wait 5 minutes before proceeding.
2. Turn on electrical supply and manual gas valve.
3. Set system switch selector at HEAT position and fan
switch at AUTO. or ON position. Set heating temper-
ature lever above room temperature.
4. The induced--draft motor will start.
5. After a call for heating, the main burners should light
within 5 seconds. If the burner does not light, then
there is a 22--second delay before another 5--second
try. If the burner still does not light, the time delay is
repeated. If the burner does not light within 15
minutes, there is a lockout. To reset the control, break
the 24 v power to W1.
6. The evaporator--fan motor will turn on 45 seconds
after burner ignition.
7. The evaporator--fan motor will turn off in 45 seconds
after the thermostat temperature is satisfied.
8. Adjust airflow to obtain a temperature rise within the
range specified on the unit nameplate.
NOTE: The default value for the evaporator--fan motor
on/off delay is 45 seconds. The Integrated Gas Unit
Controller (IGC) modifies this value when abnormal limit
switch cycles occur. Based upon unit operating conditions,
the on delay can be reduced to 0 seconds and the off delay
can be extended to 180 seconds. When one flash of the
LED is observed, the evaporator--fan on/off delay has
been modified.
If the limit switch trips at the start of the heating cycle
during the evaporator on delay, the time period of the on
delay for the next cycle will be 5 seconds less than the
time at which the switch tripped. (Example: If the limit
switch trips at 30 seconds, the evaporator--fan on delay for
the next cycle will occur at 25 seconds.) To prevent
short--cycling, a 5--second reduction will only occur if a
minimum of 10 minutes has elapsed since the last call for
heating.
The evaporator--fan off delay can also be modified. Once
the call for heating has ended, there is a 10--minute period
during which the modification can occur. If the limit
switch trips during this period, the evaporator--fan off
delay will increase by 15 seconds. A maximum of 9 trips
can occur, extending the evaporator--fan off delay to 180
seconds.
To restore the original default value, reset the power to the
unit.
To shut off unit, set system selector switch at OFF
position. Resetting heating selector lever below room
temperature will temporarily shut unit off until space
temperature falls below thermostat setting.
Ventilation (Continuous Fan)
Set fan and system selector switches at ON and OFF
positions, respectively. Evaporator fan operates
continuously to provide constant air circulation. When the
evaporator--fan selector switch is turned to the OFF
position, there is a 30--second delay before the fan turns
off.
48TC