Carrier 48DU Installation Instructions Manual page 21

S In high stage, fan is off when outdoor coil temp is <outdoor
air temperature +3_F or outdoor fan has been ON for 30
minutes. (Fan is turned off to allow refrigerant system to
stabilize.)
S In low stage, fan is off when outdoor coil temp is <outdoor air
temperature +1_F or outdoor fan has been ON for 30 minutes.
(Fan is turned off to allow refrigerant system to stabilize.)
S In high stage and low stage, fan is on when outdoor coil temp
> outdoor air temperature +25_F or outdoor coil temp > 80_F
or if outdoor fan has been OFF for 30 minutes. (Fan is turned
on to allow refrigerant system to stabilize.)
S Low- -pressure switch is ignored for first 3 minutes during low
ambient start up. After 3 minutes, if LPS trips, then outdoor
fan motor is turned off for 10 minutes with the compressor
running. If LPS closes within 10 minutes then cooling
continues with the outdoor fan cycling per the coil
temperature routine listed above for the remainder of the
cooling cycle. If the LPS does not close within 10 minutes,
then the normal LPS trip response (shut down cooling
operation and generate LPS trip error) will occur.
DEHUMIDIFICATION MODE
This Infinity system can be used to dehumidify the living space. See
UI Installation Instructions for more details.
SEQUENCE OF OPERATION- -GAS HEAT
NOTE: Infinity control must be grounded for proper operation or
control will lock out.
NOTE: If a power interruption occurs during a call for heat, the
control will start a 90- -second blower only ON period two seconds
after power is restored, if the UI is still calling for gas heating. The
amber LED light will flash code 12 during the 90- -second period,
after which the LED will be ON continuously, as long as no faults
are detected. After the 90- -second period, the unit will respond to the
UI normally.
GAS HEAT MODE AND ADJUSTMENTS
When the UI calls for gas heat, the Infinity furnace board performs
a self- -check, verifies the pressure switch is open, and starts the
inducer on high speed.
1. Inducer Pre- -purge Period: When the inducer motor comes
up on high speed, the pressure switch closes, and the Infinity
ignition control on the furnace board begins a 15 second
pre- -purge period. If the pressure switch fails to remain
closed, the inducer will remain running. After the pressure
switch re- -closes, the Infinity ignition control will begin a 15
second pre- -purge period.
2. Trial- -For- -Ignition Sequence: The spark igniter will spark
for 3 seconds. The main gas valve relay contact closes to
energize the gas valve on low stage. After 5 seconds, the
igniter is de- -energized and a 2- -second flame- -proving
period begins. NOTE: The unit always lights on high speed
inducer and low stage gas valve operation.
3. Flame- -Proving: When the burner flame is proved at the
flame- -proving sensor, the furnace control determines what
heating stage to run based on feedback from the UI. If the UI
is asking for low stage gas heat, the ignition control will
change the inducer speed to low speed and keep the gas valve
energized on low stage. If the UI is asking for high stage gas
heat, the ignition control will maintain running the inducer
on high speed and energize the gas valve's high stage relay
to increase gas flow.
If the burner flame is not proved within 2 seconds, the control will
close the gas valve and repeat the ignition sequence up to 3 more
Trials- -For- -Ignition before going to Ignition- -Lockout. Lockout
will reset automatically after 3 hours, by momentarily interrupting
230 VAC power, or by interrupting 24 VAC power at SEC1 or SEC2
to the furnace board.
If flame is proved when there should be no flame present, control
will lock out of Gas- -Heating mode and operate the inducer motor
until flame is no longer proved.
4. Blower- -On Delay:
approximately 37 seconds after the gas valve is opened the
Indoor Blower is turned on to the appropriate speed for the
gas heating stage.
Simultaneously, the humidifier terminal HUM and electronic air
cleaner terminal EAC- -1 are energized throughout the heating cycle.
NOTE: EAC- -2 terminal is common with L2 and will have
115VAC- -to- -ground when unit is powered.
5. Blower- -Off Delay: When the call for gas heat is satisfied, the
gas valve is de- -energized, stopping the flow of gas to the
burners, and de- -energizing the HUM terminal. The inducer
motor will remain on for a 4- -second post- -purge period. The
indoor blower and air cleaner terminal EAC- -1 will remain
energized for 90, 120, 150, or 180 seconds (depending on
selection of blower- -off delay selected in the UI). The
factory- -set default is 120- -second blower- -OFF delay.
CHECK GAS INPUT (NATURAL GAS)
CAUTION
!
UNIT DAMAGE HAZARD
Failure to follow this caution may result in component
damage due to flame impingement of burners and heat
exchangers.
Do not redrill an orifice. Improper drilling (burrs,
out- -of- -round holes, etc.) can cause excessive burner noise
and misdirection of burner flame. If orifice hole appears
damaged or it is suspected to have been redrilled, check orifice
hole with a numbered drill bit of correct size.
WARNING
!
FIRE HAZARD
Failure to follow this warning could result in personal injury,
death and/or property damage.
DO NOT bottom out gas valve regulator adjusting screws.
This can result in unregulated manifold pressure and result in
excess overfire and het exchanger failures.
WARNING
!
CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in personal injury,
death and/or property damage.
If the manifold pressure and/or gas rate is not properly
adjusted on HI and LO stages, excess carbon monoxide can be
produced.
WARNING
!
FIRE AND UNIT DAMAGE HAZARD
Failure to follow this warning could result in personal injury
or death and/or property damage.
Unsafe operation of the unit may result if manifold pressure is
outside of the ranges listed in Table 7.
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If the burner flame is proven,