White-Rodgers White-Rodgers 50A50/50A51 Fault Diagnostics Pressure Switch Problem 50A51-495/-506/-507 Two Stage Variable-Speed Systems The induced draft motor will always be energized to high speed. The induced draft motor will be energized to low speed when the Control senses the 1st stage pressure switch contacts have closed. If the 1st stage pressure switch contacts open during a normal 1st stage heating cycle, the gas valve will be de-energized to remove the flame and the induced draft motor will be energized to high speed for 10 minutes. If the 1st stage pressure switch contacts close during the 10 minute high speed purge, the Control will restart the ignition sequence.
If the 1st stage pressure switch contacts remain closed after 10 minutes, the induced draft motor will be energized to low speed and a normal heating operation will continue. If the pressure switch contacts do not close after 10 minutes, the induced draft motor will be energized again to high speed for 10 minutes and the diagnostic LED will begin flashing 3 times to indicate a pressure switch problem. Recycling the induced draft motor will continue as long as a 1st stage call for heat exists and the Control will not go into lockout. The 2nd stage pressure switch fault diagnostic operation is the same as 50A51-405/-505 Controls. CNT2789 13 Thermal Protection Devices At any time during a call for heat, if the Control senses the high temperature limit (and/or aux.
Limit) or flame roll out switch(es) are open, the gas valve is de-energized, the induced draft motor is energized (low speed on 50A51 Controls), and the indoor blower is energized to run on heat speed. On models utilizing fusible link devices, the fusible link is a single use device and must be replaced if it has opened. However, if the temperature the fusible link senses is approaching the trip temperature but does not exceed it, the contacts may open and close intermittently. The Control will initiate another ignition sequence upon the closure of the intermittent fusible link. Flame Sensed With Gas Valve Off At any time the Control senses a flame current signal without a call for heat or when the gas valve is de-energized, the induced draft motor is energized (low speed on 50A51 Controls), and the indoor blower is energized to run on heat speed.1 The Control will go into system lockout and will not reset until this fault is corrected. The diagnostic LED will begin flashing 5 times to indicate the flame sensed with the gas valve de-energized. 1 See Integrated Furnace Control Label or Timing Chart.
View and Download White Rodgers 50A55-843 user manual online. Universal Integrated Furnace Control. 50A55-843 Controller pdf manual download. White Rodgers Manuals. 50A55 INTEGRATED FURNACE CONTROL MODULE. NOTE: This troubleshooting guide is not for 50A55-4XX modules found on Trane equipment or 50A55-1XX modules found on Lennox equipment.
White-Rodgers 50A55-571/-474 Self Diagnostic Features 1 OFF 1 2 3 4 DS2 COOL-H PARK PARK LINE-H E17 E28 E27 E13 HEAT-H XFMR-H E16 E18 E14 K2 ON DS1 K1 K3 C4 E4 K5 Y W R G C E4 LINE-N E7 E8 E9 XFMR-N E10 CIR-N E11 K6 FUSE1 E1 Slow Flash – Normal, No Call For Heat Present. Fast Flash – Normal, Call For Heat Present. Continuous On – Internal Control Failure. Diagnostic Indicator Flash Codes: 2 Flashes – System Lockout (Retries or Recycles Exceeded). 3 Flashes – Pressure Switch Stuck Open or Closed. 4 Flashes – Open High Temperature Limit Switch.
5 Flashes – Flame Sensed Without Gas Valve. Solution manual for experimental methods for engineering. 6 Flashes – 115 Volt AC Power Reversed.
50a50 472 Control Board
7 Flashes – Gas Valve Circuit Error. 8 Flashes – Low Flame Sense Signal. See Pages 14 and 15 for Sequence of Operation and Wire Schematic. 1 Fuse only on 474 Model and Dip Switches replace jumpers. Single Stage 50A50 and 50A55 Sequence of Operation White-Rodgers Integrated Furnace Controls 50A50-405/-406/-471/-472/ -473/-474/-571 and 50A55-571/-474 Models When the disconnect 1 is in the “ON” position, power is applied through the blower door interlock switch 6 to the control line voltage input terminal 8 and out of the control to the primary side of the control transformer “XFMR” 9. The low voltage side of the transformer supplies 24 volts to the control through terminals “TH” o and “TR” i. Control terminal “R”; supplies 24 volts to the “R” terminal of the room thermostat.
Once power is applied, the control flashes the LED “ON” for 1 second and performs a self check routine. Following the normal system check, the control flashes the LED light once per second continuously (slow flash) while in stand-by.
On a call for heat, 24 volts is applied from the thermostat terminal “W” to the “W” terminal; on the control. The control checks and confirms normally closed contacts at the temperature cut out “TCO” f, the auxillary limit (downflow and some upflow/horizontal models), the flame roll-out fuse link (two fuse links are used on downflow and upflow/horizontal models) f and j and normally open contacts of the safety pressure switch “PS” f. With all safety and control switches in their proper position, the control will energize the induced draft motor y and flash the LED light two times per second continuously (fast flash) during a call for heat.
When the safety pressure switch “PS” f closes, the control begins the ignition sequence. The hot surface ignitor y is energized for several seconds (see note) allowing the thermal element to heat up. The control then switches on 24 volts to the gas valve “MV” termi- 14 nals #1 a.
The redundant and main solenoids are energized allowing gas flow and main burner ignition. When flame current is detected by the control through its terminal “FP” k, the 45 second indoor blower motor delay on timing begins. Flame failure response time is set for 2 seconds. After flame has been established for ten seconds, the flame failure response time is reset for 0.7 seconds. If flame current is not sensed by the control k within the trial for ignition period (see note), the redundant and main gas valve solenoids a are de-energized. The control will begin a interpurge cycle and adds additional seconds to the hot surface ignitor warm-up timing (see note).
The control energizes the gas valve a for the second attempt to establish main burner ignition. If flame current is not sensed by the control on the 2nd retry within the trial for ignition period (see note), the control will repeat the previous cycle one additional time before locking out. At the end of the indoor blower delay on time, line voltage is applied at the controls terminal “HEAT” 5 energizing the indoor blower motor at heating fan speed, supplying warm air to the space. When the thermostat is satisfied, the gas valve’s redundant and main solenoids a are de-energized, extinguishing main burner flame. Once the control senses loss of flame current (0.7 sec.) k, the induced draft motor t is de-energized after a five second post purge cycle. The indoor blower motor delay off timing begins.
At the completion of the fan delay off timing, the indoor blower motor 5 is de-energized and the cycle is complete. Note: See Timing Chart for details or Integrated Furnace Control Label.