Carrier 48TC 04 Series, Service And Maintenance Instructions

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Refer to Table 16 through Table 20 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