Self Diagnostic Features 50A50 And 50A51; Led Flash Rate - American Standard *UD Series Operation Manual

White-Rodgers Self Diagnostic Features – 50A50/50A51 Series
The integrated furnace control incorporates system
fault analysis for quick gas flow shutoff, coupled with
automatic ignition retry upon sensing a fault correction.
The integrated furnace control tests for internal
and external faults before allowing a heating
sequence to begin. The external check includes all
safety devices and pressure switches, making
certain that they are in their proper normally open
or normally closed position. If a fault is detected
by the control, it will immediately enter into a
fault mode and flash the LED light according to
the fault detected, see LED Flash Rate table at right.
The control will remain in the fault mode until the
problem is corrected. Once the fault is cleared, the
control will start the heating sequence as long as the
call for heat still exists.
The control has an expanded diagnostic feature that
monitors system performance. If a fault is detected
during operation, the control will de-energize the gas
valve and flash the diagnostic LED according to the
fault detected (see LED flash rate Table 3).
The control will automatically reset a lock-out due
to loss of flame. See I.F.C. Timing Table for reset time,
see page 10.
Important:
The control is mounted in the blower section.
Do not remove blower door before checking
flash rate of LED. Sight glass is provided on
upflow models in the blower door panel to prevent
resetting control and loss of diagnostics.
1 This fault will be caused if the hot leg and neutral leg of
!
9

LED Flash Rate

Normal Operation
• The LED will flash for 1 second at power-up
• the LED will flash "FAST", 1/4 second "ON" and
1/4 second "OFF", during a call for heat
• The LED will flash "SLOW", 1/4 second "ON" and
3/4 seconds "OFF" with system in stand-by
(power on).
Note: The LED will flash "ON" for approximately
1/4 second, then "OFF" for approximately 1/4 second.
The pause between groups of flashes is approximately
2 seconds.
Fault Diagnostic
Continuous ON – Internal Fault, or grounded
sensor (Lockout)
2 Flashes – System Lockout – No Flame1
3 Flashes – Pressure Switch Error
4 Flashes – Thermal Protection
Device Open
5 Flashes – Flame Sensing With Gas Valve
De-Energized
(Stuck Open)
the 120 volt A.C. power legs are reversed.
Diagnostic
LED
(Red)