Heating - Carrier 48LC Installation Instructions Manual

Select Switch is in the down position, the outdoor fans will
run in the Minimum Fan Speed Mode (MIN) set to 160 rpm
regardless of the cooling demand.
LC Size 07 Units have a SPST normally open Low
Ambient Switch wired across the TS and OF terminal and
a jumper placed across the PS terminal (see Fig. 42).
When the LAS is active, the switch will close making
contact to the OF terminal. This is done for units that
require all outdoor fans to run at the same pre- - set factory
Low Ambient Speed.
OF SPEED
SELECT
FCS
MIN
DOWN
Fig. 41 - - Outdoor Fan Speed Select Switch
JUMPER ON
PS
TS
SPST
Fig. 42 - - Schematic of SPST Low Ambient Switch
The Low Ambient Temperature Outdoor Fan Control
Table (below) shows the operation of the outdoor fan for
size 07 units.
Table 5 – Low Ambient Temperature Outdoor Fan Control
No. of No. of
LC Size
Fans On Fans Off
07 2 0
UP
C13327
PS
OF
LAS
C13328
Outdoor Fan
Switch RPM
Select Switch
SPST Up 250
Heating —
In the Heating Mode (W1 and G on the thermostat), the
ISC board sends power to W on the IGC board. Assuming
the unit is controlled through a room thermostat set for fan
auto, the indoor- - fan motor will energize and the
outdoor- - air dampers will open to their minimum position.
The ISC board upon seeing W1 and G ON will turn the
indoor fan to high speed
The IGC board starts its gas ignition process. A check is
made to ensure that the rollout switch and limit switch are
closed. If the check was successful, the induced draft
motor is energized, and when its speed is satisfactory, as
proven by the "hall effect" sensor, the ignition activation
period begins. The burners will ignite within 5 seconds. If
the burners do not light, there is a 22- - second delay before
another 5 second attempt. This sequence is repeated for 15
minutes or until the burners light. If, after the 15 minutes,
the burners still have not lit, heating is locked out. To
reset the control, break 24VAC power to the thermostat.
When gas ignition occurs, the IGC board will continue to
monitor the condition of the rollout switch, the limit
switches, the "hall effect" sensor, as well as the flame
sensor.
When W1 is turned OFF, the IGC board turns off the gas
valve. The IGC board has a delay time before it turns
IFO=OFF. At this time, the ISC board sees W1=OFF and
IFO=ON. The ISC will keep the indoor fan ON high
speed. Once the IGC board delay times out, the ISC board
will see W1=OFF and IFO=OFF, which then turns the
indoor fan OFF.
If the call for W1 lasted less than 1 minute, the heating
cycle will not terminate until 1 minute after W1 became
active. If the unit is controlled through a room thermostat
set for fan auto, the indoor fan motor will continue to
operate for an additional 45 seconds then stop. If the over
temperature limit opens after the indoor motor is stopped,
but within 10 minutes of W1 becoming inactive, on the
next cycle the time will be extended by 15 seconds. The
maximum delay is 3 minutes. Once modified, the fan OFF
delay will not change back to 45 seconds unless power is
reset to the control. A LED indicator is provided on the
IGC to monitor operation.
When additional heat is required, W2 closes and initiates
power to the second stage of the main gas valve. When
the thermostat is satisfied, the gas valve closes,
interrupting the flow of gas to the main burners.
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