OPERATION
OPTION SWITCHES
Ifflameisdetected,thenlost,the50A55controlwillrepeat
the initial ignition sequence for a total of four “recycles”.
Theoptionswitchesonthe50A55-286controlareusedto After four unsuccessful “recycle” attempts, the control will
determine the length of the heat delay-to-fan-off periods. go into system lockout.
The following table shows the time periods that will result
from the various switch positions.
If flame is established for more than 10 seconds after
ignition, the50A55controllerwillcleartheignitionattempt
(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.
OPTION SWITCH POSITIONS
HEAT delay-
to-fan-off:
Set switch
#1
#2
Duringburneroperation, amomentarylossofpowerof50
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.
60 sec.*
90 sec.
120 sec.
180 sec.
On
Off
On
Off
On
On
Off
Off
*Factory set position
A momentary loss of gas supply, flame blowout, or a
shorted or open condition in the flame probe circuit will be
sensed within 2.0 seconds. The gas valve will de-ener-
gize and the control will restart the ignition sequence.
Recycles will begin and the burner will operate normally
ifthegassupplyreturns,orthefaultconditioniscorrected,
before the last ignition attempt. Otherwise, the control will
go into system lockout.
HEAT MODE
In a typical system, a call for heat is initiated by closing the
thermostat contacts. This starts the 50A55 control’s heat-
ing sequence. The inducer blower and optional humidifier
are energized and the ignitor is powered.
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.
Theignitoristhenallowedtowarmupfor17seconds.The
120 VAC ignitors with a 17 second warm-up time
manufacturedbyCarborundum,IgnitorSystems,Inc.,
or Norton must be used. These ignitors are specially
designed to heat up quickly at a low voltage condition
without overheating at a high voltage condition.
COOL 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 7 seconds.
In a typical system, a call for cool is initiated by closing the
thermostat contacts. This energizes the 50A55 control.
The compressor and optional electronic air cleaner are
energized, and the circulator fan is energized at cool
speed. After the thermostat is satisfied, the compressor is
de-energized and the cool mode delay-to-fan-off period
begins. After the cool delay-to-fan-off period ends, the
circulator fan and electronic air cleaner are de-energized.
If flame is detected, the delay-to-fan-on period begins.
After the delay-to-fan-on period ends, the optional elec-
tronic air cleaner is powered and the circulator fan is
energized at heat speed. When the thermostat is satis-
fied, the gas valve is de-energized. After proof of flame
loss, the heat delay-to-fan-off period begins and the
inducerblowerremainsenergizedtopurgethesystemfor
15 seconds. When the purge is complete, the inducer
blower and humidifier are de-energized. After the delay-
to-fan-off period ends, the circulator fan and electronic air
cleaner are de-energized.
MANUAL FAN ON MODE
If the thermostat fan switch is moved to the ON position,
the circulator fan (cool speed) and optional electronic air
cleaner are energized. When the fan switch is returned to
the AUTO position, the circulator fan and electronic air
cleaner (optional) are de-energized.
If flame is not detected, both valves are de-energized, the
ignitor is turned off, and the 50A55 control goes into the
“retry” sequence. The “retry” sequence provides a 15-
second wait following an unsuccessful ignition attempt
(flame not detected). After this wait, the ignition sequence
is restarted with an additional 11 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.
6