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6
OPERATION
OPTION SWITCHES
The option switches on the 50A55-286 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.
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.
The ignitor is then allowed to warm up for 17 seconds. The
120 VAC ignitors with a 17 second warm-up time
manufactured by Carborundum, Ignitor Systems, 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.
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.
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
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 period ends, the circulator fan and electronic air
cleaner 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.
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.
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.
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.
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
if the gas supply returns, or the fault condition is corrected,
before the last ignition attempt. Otherwise, the control will
go into system lockout.
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.
COOL MODE
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.
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.
HEAT delay-
to-fan-off:
Set switch
#1 #2
60 sec.*
90 sec.
120 sec.
180 sec.
On On
Off On
On Off
Off Off
OPTION SWITCH POSITIONS
*Factory set position