Normal Operation; Airflow And Temperature Rise; Heating Sequence Of Operation; Limit Switches - Carrier Performance 48VG-E Installation Instructions Manual

Normal Operation

An LED (light- -emitting diode) indicator is provided on the
integrated gas unit controller (IGC) to monitor operation. The IGC
is located by removing the control access panel (see Fig. 22).
During normal operation, the LED is continuously on (See Table 8
for error codes).

Airflow and Temperature Rise

The heating section for each size unit is designed and approved for
heating operation within the temperature- -rise range(s) stamped on
the unit rating plate.
Tables 13, 14 and 15 show the approved temperature rise range for
each heating input and stage, and the air delivery cfm at various
temperature rises for a given external static pressure. The heating
operation airflow must produce a temperature rise that falls within
the approved range for each heating stage. For single phase units
only, "High" blower speed is for high static, high stage cooling and
must not be used for gas heating speed.
Refer to Indoor Airflow and Airflow Adjustments section to adjust
heating airflow when required.

Heating Sequence of Operation

(See Fig. 15, 16, 17 and unit wiring label.)
208/230 VAC Models:
On a call for low stage heating, terminal W1 on the thermostat is
energized. On a call for high stage heating both terminals W1 and
W2 are energized. Regardless of the stage of the heating call, the
induced- -draft motor is turned on to high speed for a 15 sec
pre- -purge time. After the pre- -purge, when the pressure switch
senses that sufficient combustion air is being moved by the
induced- -draft motor, the ignition sequence begins. The IGC will
energize the sparker and the low stage gas valve solenoid. Upon
sensing flame, the IGC will check the heating call. If W2 is not
energized, the IGC will drop the induced- -draft motor to low speed
and maintain the gas valve on low stage. If W2 is energized, the
IGC will maintain the induced- -draft motor on high speed and
energize the high stage gas valve solenoid. Thirty sec after flame is
sensed the IGC will turn on the evaporator fan motor. If W2 is not
energized, the evaporator fan motor will run on low heat speed. If
W2 is energized, the evaporator fan motor will run on high heat
speed. After the call for heat is satisfied, the IGC will run the
evaporator fan motor an additional field- -selectable time of 90, 120,
150, or 180 sec before shutting the evaporator fan motor off.
460 VAC Models:
On a call for heating, terminal W of the thermostat is energized,
starting the induced- -draft motor. When the pressure switch senses
that the induced- -draft motor is moving sufficient combustion air,
the ignition sequence begins. This function is performed by the
integrated gas unit controller (IGC). The indoor (evaporator)- -fan
motor is energized 45 sec after flame is established. When the
thermostat is satisfied and W is de- -energized, the burners stop
firing and the indoor (evaporator) fan motor shuts off after a
45- -sec time- -off delay. Please note that the IGC has the capability
to automatically reduce the indoor fan motor on delay and increase
the indoor fan motor off delay in the event of high duct static
and/or partially- -clogged filter.

Limit Switches

Normally closed limit switch(es) (LS) complete the control circuit.
Should the leaving- -air temperature rise above the maximum
allowable temperature, the limit switch opens and the control
circuit "breaks." Any interruption in the control circuit instantly
closes the gas valve and stops gas flow to the burners. The blower
motor continues to run until LS resets.
When the air temperature at the limit switch drops to the
low- -temperature setting of the limit switch, the switch closes and
completes the control circuit. The direct- -spark ignition system
cycles and the unit returns to normal heating operation.
Table 8 – LED Indications
STATUS CODE
2
Normal Operation
No Power or Hardware Failure
Check Fuse, Low Voltage Circuit
Limit Switch Fault
Flame Sense Fault
Four Consecutive Limit Switch Faults
Ignition Lockout Fault
Pressure Switch Fault
Rollout Switch Fault
Internal Control Fault
Temporary 1 hr auto reset
NOTES:
1.This code indicates an internal processor fault that will reset itself in one
hr. Fault can be caused by stray RF signals in the structure or nearby. This
is a UL requirement.
2. LED indicates acceptable operation. Do not change ignition control
board.
3. When W is energized the burners will remain on for a minimum of 60 sec.
4. If more than one error code exists they will be displayed on the LED in
sequence.

Rollout Switch

The function of the rollout switch is to close the main gas valve in
the event of flame rollout. The switch is located above the main
burners. When the temperature at the rollout switch reaches the
maximum allowable temperature, the control circuit trips, closing
the gas valve and stopping gas flow to the burners. The indoor
(evaporator) fan motor (IFM) and induced draft motor continue to
run until switch is reset. The IGC LED will display FAULT CODE
7.
Step 3 — Start- -up Cooling and Make Adjust-
ments
Complete the required procedures given in the Pre- -Start- -Up
section before starting the unit. Do not jumper any safety devices
when operating the unit. Do not operate the compressor when the
outdoor temperature is below 40F
low- -ambient kit is installed). Do not rapid- -cycle the compressor.
Allow 5 minutes between on cycles to prevent compressor damage.

Checking Cooling Control Operation

Start and check the unit for proper control operation as follows:
1. Place room thermostat SYSTEM switch or MODE control
in OFF position. Observe that blower motor starts when
FAN mode is placed in FAN ON position and shuts down
when FAN MODE switch is placed in AUTO position.
2. Thermostat:
On a typical two stage thermostat, when the room temper-
ature rises 1 or 2 degrees above the cooling control setting
of the thermostat, the thermostat completes the circuit
between thermostat terminal R and terminals Y1, and G.
These completed circuits through the thermostat connect the
contactor coil (C) (through unit wire Y1) and indoor fan
board (through unit wire G) across the 24- -v. secondary of
transformer (TRAN).
On a typical two stage thermostat, when the room temperat-
ure is several degrees above the cooling control setting of
the thermostat, the thermostat completes the circuit between
terminal R and terminals T1, Y2 , and G.
3. When using an automatic changeover room thermostat
place both SYSTEM or MODE control and FAN mode
stitches in AUTO positions. Observe that unit operates in
Cooling mode when temperature control is set to "call for
Cooling" (below room temperature).
NOTE: Once the compressor has started and then has stopped, it
should not be started again until 5 minutes have elapsed.
IMPORTANT: Three- -phase, scroll compressors are direction
oriented. Unit must be checked to ensure proper compressor
28
LED INDICATION
On
Off
1 Flash
2 Flashes
3 Flashes
4 Flashes
5 Flashes
6 Flashes
7 Flashes
8 Flashes
1
9 Flashes
(4.4C) (unless accessory