OPERATION
OPTION SWITCHES
The option switches on the 50A55-285 control are used to
determine the length of the heat delay-to-fan-off periods. The
following table shows the time periods that will result from the
various switch positions.
Ifflameisnotdetected, bothvalvesarede-energized, theignitor
is turned off, and the 50A55 control goes into the “retry” se-
quence. The “retry” sequence provides a 60-second wait follow-
ing an unsuccessful ignition attempt (flame not detected). After
this wait, the ignition sequence is restarted with an additional 2
seconds of ignitor warm-up time. If this ignition attempt is
unsuccessful, one more retry will be made before the control
goes into system lockout.
OPTION SWITCH POSITIONS
If flame is detected, then lost, the 50A55 control will repeat the
initial ignition sequence for a total of four “recycles”. After four
unsuccessful “recycle” attempts, the control will go into system
lockout.
HEAT delay-
to-fan-off:
Set switch
#1
#2
60 sec.
90 sec.*
120 sec.
On
Off
On
Off
On
On
Off
Off
If flame is established for more than 10 seconds after ignition,
the 50A55 controller will clear the ignition attempt (or retry)
counter. If flame is lost after 10 seconds, it will restart the ignition
sequence. This can occur a maximum of five times before
system lockout.
180 sec.
* Factory setting
During burner operation, a momentary loss of power of 50
milliseconds or longer will de-energize the main gas valve.
When power is restored, the gas valve will remain de-energized
and a restart of the ignition sequence will begin immediately.
HEAT MODE
In a typical system, a call for heat is initiated by closing the
thermostat contacts. This starts the 50A55 control’s heating
sequence. The inducer blower and optional humidifier are
energized and the ignitor is powered within one second.
A momentary loss of gas supply, flame blowout, or a shorted or
openconditionintheflameprobecircuitwillbesensedwithin2.0
seconds. The gas valve will de-energize and the control will
restarttheignitionsequence. Recycleswillbeginandtheburner
will operate normally if the gas supply returns, or the fault
condition is corrected, before the last ignition attempt. Other-
wise, the control will go into system lockout.
This controller has an adaptive algorithm that adjusts the dura-
tion of the ignitor warm-up, to extend ignitor life. Upon initial
application of power, the warm-up time is 17 seconds. The
ignitor on-time will then be increased or decreased depending
onwhetherornotflameisachieved. Thewarm-uptimeislimited
to a maximum of 21 seconds. During the first 64 warm-up
periods following power-up, the warm-up time may not be less
than 17 seconds.
If the control has gone into system lockout, it may be possible to
reset the control by a momentary power interruption of one
second or longer. Refer to SYSTEM LOCKOUT FEATURES.
Upon a call for heat, if the warm-up time has not been locked, it
willbedecreasedbyonesecond.Thisreductionoftheignitoron-
time will continue until flame fails to be achieved (resulting in a
retry).
COOL MODE
In a typical system, a call for cool is initiated by closing the
thermostat contacts. This energizes the 50A55 control and the
compressor. The cool delay-to-fan-on period begins. After the
delay period ends, the optional electronic air cleaner is ener-
gized, and the circulator fan is energized at cool speed. After the
thermostat is satisfied, the compressor is de-energized and the
coolmodedelay-to-fan-offperiodbegins. Afterthedelay-to-fan-
off period ends, the circulator fan and electronic air cleaner
(optional) are de-energized.
In the event of a retry, the warm-up time will be increased by two
seconds and locked in at that duration. Once the warm-up time
is locked, it remains fixed until another call for heat results in a
retry, in which case the warm-up time is again increased by two
seconds and remains locked.
In the event of two successive retry attempts, the warm-up time
willbeunlockedandsetto21seconds. Ifflameisthenachieved,
the warm-up time will begin adapting again with the next call for
heat. If, however, this third attempt fails to achieve flame, the
control will go into system lockout.
MANUAL FAN ON MODE
At the end of the ignitor warm-up time, both valves in the 36E
manifold gas valve are opened. Flame must be detected within
4 seconds.
If the thermostat fan switch is moved to the ON position, the
circulatorfan(coolspeed)andoptionalelectronicaircleanerare
energized. When the fan switch is returned to the AUTO posi-
tion, the circulator fan and electronic air cleaner (optional) are
de-energized.
If flame is detected, the delay-to-fan-on period begins. After the
delay-to-fan-on period ends, the optional electronic air cleaner
is energized and the circulator fan is energized at heat speed.
When the thermostat is satisfied, the gas valve is de-energized.
After proof of flame loss, the heat delay-to-fan-off period begins
and the inducer blower remains energized to purge the system
for 15 seconds. When the purge is complete, the inducer blower
and humidifier are de-energized. After the delay-to-fan-off pe-
riod ends, the circulator fan and electronic air cleaner are de-
energized.
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