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OPERATION
I
OPTION SWITCHES
The opfion switches on the 50A55-84i] control are used to
determlne the length of the cool delay-to-fan-off, heat delay-to-
fan-on and heat delay-to-fan-off periods. The following table
shows the time periods that will result from the various switch
positions.
oPTroN swtTcH PostTtoNs
COOL delay-
to-fan-off:
Set switch
#1
45 sec.*
90 sec.
On
off
HEAT delay-
to-fan-off:
Set switch
u
#!
60 sec.
90 sec.
120 sec.
180 sec.*
On
On
Off
On
On
Off
off
off
* Factory setting
HEAT MODE
In a typixl system, a call for heat is initiated by closing the
thermostat contacts. This starts the 5OA55 confol's heatng
sequence. The inducer blower and optional humidifier are
energized and the lgnitor is powered within one second.
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
on whetheror notflame is achieved. Thewarm-uptime is limited
to a maxlmum of 21 seconds. During the first 64 warm-up
periods following power-up, the warm-up time may not be less
than 17 seconds.
Upon a call for heat, if the warm-up time has not been locked, il
willbedecreased byone second. This reduction of the ignitoron-
time will continue until flame lails to be achieved (resulting in a
retry).
ln 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
will be unlocked and set to 21 seconds. lf fl ame is then achieved,
the warm-up time will begin adapting again with the next call for
heat. lf, however, this third attempt fails to achieve flame, the
control will go into system lockout.
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.
lf 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-tofan-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 clrculator fan and electronic air cleaner are de-
energized.
lf flame is not detected, both valves are de-energized, the ignitor
is turned off, and the 50A55 control goes into the "ret4f se-
quence. The "retq/ sequence provides a GG.second waitfollow-
ing an unsu@essful ignition attempt (flame not detected). After
this wait, the ignition sequence is restarted with an additional 2
seconds of ignitor warm-up time. lf this ignition attempt is
unsuccessful, one more retry will be made before the control
goes into system lockout.
lf flame is detected, then lost, the 50455 control will repeat the
initial ignition sequence for a total ol four "recycles". After four
unsuccessful "recycle" attempts, the control will go into system
lockout.
lf flame is established for more tlmn 10 seconds after ignition,
the 50A55 controller wrll dear the rgnitirn attempt (or retry)
countef. lf flame is lostafter'10 seconds, rtwrll restartthe Onition
sequence. This can occur a maximum of five times before
system lockout.
During bumer 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 wlll 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 wthin 2.0
secpnds. The gas valve will de'energlze and the confol wrll
restart the ignition sequen@. Recydes will @in and the bumer
will operate normally if the gas supply retums, or the fault
condition is corrected, before the last ignition attempt. Other-
wise, the control will go into system lockout.
lf the control has gone into system lockout, it may be possible to
reset the control by a momentary power intenuption of one
second or longer. Refer to SYSTEM LOCKOUT FEATURES.
COOL MODE
ln 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 circulatorfan is energized at cool speed. Afterthe
thermostat is satisfied, the compressor is de-energized and the
cool mode delay-to-fan-off perlod begins. Afterthe delay-to-fan-
off period ends, the circulator fan and electronic air cleaner
(optional) are de-energized.
MANUAL FAN ON MODE
lf the thermostat fan switch is moved to the ON position, the
circulatorfan (cool speed) and optional electronic air cleanerare
energized. When the fan switch is retumed to the AUTO posi-
tion, the circulator fan and electronic air cleaner (optional) are
de-energized.
HEAT delay-
to-fan-on:
Set switch
#2
30 sec.-
45 sec.
On
off
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