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7
SYSTEM LOCKOUT FEATURES
When system lockout occurs, the gas valve is de-energized,
the circulator blower is energized at heat speed, and, if flame
is sensed, the inducer blower is energized. The diagnostic
indicator light will flash or glow continuously to indicate
system status. (System lockout will never override the
precautionaryfeatures.)
To resetthe controlafter systemlockout,do one of the
following:
1. Interrupt the call for heat or cool at the thermostat for at
least one second but less than 20 seconds (if flame is
sensed with the gas valve de-energized, interrupting the
call for heat at the thermostat will not reset the control).
2. Interrupt the 24 VAC power at the control for at least one
second. You may also need to reset the flame rollout
sensor switch.
3. After one hour in lockout, the control will automatically
reset itself.
DIAGNOSTIC FEATURES
The 50M56-743 control continuously monitors its own
operation and the operation of the system. If a failure occurs,
the LED will indicate a failure code as shown on page 8. If
thefailureisinternaltothecontrol,theLEDwillstayoff
orash8times.Inthiscase,theentirecontrolshouldbe
replaced,asthecontrolisnoteld-repairable.
Failure codes will flash the LED in the following flash-
pause sequences to indicate failure status (each flash will
last approximately 0.25 seconds, and each pause will last
approximately 2 seconds).
FAULT RECALL
The last five fault codes stored can be displayed on the
diagnostic LED. When the control is in standby mode (no
call for heat or cool), press the FAULT RECALL switch for
approximately two seconds or until the diagnostic LED turns
off. Release the switch and the LED will remain off for two
seconds. Then the fault codes will display beginning with the
most recent fault first with a two second pause between codes.
After the stored fault codes have all displayed, the LED will
remain off for two seconds and then turn on to indicate return
to normal status. While displaying the stored fault codes, the
control will ignore any new call for heat, cool or fan.
FAULT CODE RESET
The stored fault codes can be erased from memory. When
the control is in standby mode (no call for heat or cool), press
the FAULT RECALL switch for five to ten seconds or until
the diagnostic LED begins to rapid flash. When the switch is
released, the LED will turn off for two seconds to indicate the
codes are erased. After two seconds the LED will turn on to
indicate return to normal status. If the switch is held pressed
for over ten seconds the rapid flash will stop and the LED will
be on to indicate return to normal status.
The 50M56-743 has only one serviceable part –an automotive
type fuse, which protects the low voltage transformer from
damage if the output is short-circuited. If the fuse has opened
up, remove whatever caused the short circuit and replace the
fuse with only a 3 Amp automotive type fuse. If the fuse does
not correct the condition, replace the entire 50M56-743 control.
There are no other user serviceable parts.
SYSTEM LOCKOUT AND DIAGNOSTIC FEATURES