White Rodgers 50M56U-843 - Manual (Page 7)

7
OPERATION
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 50M56U-843 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 below.
If the
failure is internal to the control, the light will stay off. In
this case, the entire control should be replaced, as the
control is not field-repairable.
If the sensed failure is in the system (external to the control),
the LED will flash 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).
DIAGNOSTIC INDICATOR FLASH CODES
FLASH
1 System Lockout (Retries Exceeded)
2 Pressure Switch Stuck Closed
3 Pressure Switch Stuck Open
4 Open High Temperature Limit Switch
5 Flame Sensed with Gas Valve De-energized
6 Open Rollout Switch
7 Low Flame Sense Signal
8 Ignitor Relay Fault
Rapid Flash
Reverse Polarity
Continuous On Normal Operation
Off
Control Failure
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.
Auto Restart – After one (1) hour of internal or external
lockout, the control will automatically reset itself and go
into an auto restart purge for 60 seconds.
Cool Delay-To-Fan-Off – The period of time between the
loss of a call for cool and the deactivation of the blower
motor at Cool speed.
Cool Delay-To-Fan-On – The period of time after a thermostat
demand for cool before energizing the circulator blower
motor at Cool speed.
Flame Failure Response Time (FFRT) – The period of time
between loss of the supervised main burner flame and
the action to shut off the gas supply.
Heat Delay-To-Fan-Off – The period of time between the
loss of a call for heat and the deactivation of the blower
motor at Heat speed.
Heat Delay-To-Fan-On – The period of time between proof
of the supervised main burner flame and the activation of
the blower motor at Heat speed.
Igniter Warm-up Time – The length of time allowed for the
igniter to heat up prior to the initiation of gas flow.
Ignition Activation Period (IAP) – The period of time
between energizing the main gas valve and deactivation
of the ignition means prior to the end of TFI.
Inter-purge – The period of time intended to allow for the
dissipation of any unburned gas or residual products of
combustion between the failed trial for ignition and the
retry period.
Post-purge Time – The period of time intended to allow for
the dissipation of any unburned gas or residual products
of combustion at the end of a furnace burner operating
cycle. Post-purge begins at the loss of flame sense.
Pre-purge Time – The period of time intended to allow for the
dissipation of any unburned gas or residual products of
combustion at the beginning of a furnace operating cycle
prior to initiating ignition.
Recycles – The additional attempts within the same
thermostat cycle for ignition after loss of the supervised
ignition source or the supervised main burner flame.
Retries – The additional attempts within the same thermostat
cycle for ignition when the supervised main burner flame
is not proven within the first trial for ignition period.
Trial for Ignition Period (TFI) – The period of time between
initiation of gas flow and the action to shut off the gas flow
in the event of failure to establish proof of the supervised
ignition source or the supervised main burner flame.
DEFINITION OF TERMS