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2. Service/Review...

3. Service/Review...

4. Start with the BASICS! Assume nothing, check everything, no matter how unrelated it may seem. Forget everything that?s been done in the past service calls. Check low voltage connections, check line voltage connections. Check voltages. Check pressures, cycle it on the thermostat. Cycle it on the safeties. Drop out a motor.

5. Start with the BASICS! (con?t) Wiggle wires, jiggle connections and look everywhere. Ignore your urges, remember that the last guy did what you?re considering and look how productive that was. What are you looking for? - Won?t know until you find it!

6. SELF DIAGNOSTIC FEATURE The IFC tests for internal & external faults before allowing a heating sequence to begin. The external check includes all safety devices & pressure switches, making certain that they are in their proper normally open or closed position. 24 volt signal leaves HLO to HLI to check limits & PS/PS1 for pressure switch. If a fault is detected the IFC will immediately enter into a fault mode and flash the LED according to the fault detected.

7. SELF DIAGNOSTIC The IFC will remain in the fault mode until the problem is corrected. Once the fault is cleared, the IFC will start the heating sequence as long as the call for heat still exists. The IFC has expanded diagnostic features that monitors the system. If a fault is detected , the IFC will de-energize the gas valve & flash the LED. The control will automatically reset a lock-out due to loss of flame, see IFC table page 10 reset time.

8. SELF DIAGNOSTIC SERVICE CALL IMPORTANT: Do not remove blower door or turn off power before checking flash rate LED. Sight glass is provided on upflow models in the blower door panel. (Pre W4, series furnaces) Note LED flash rate timing.

9. Diagnostic Code Label Flashing Slow one/ sec Normal, No Call Flashing Fast two/sec Call for Heat Continuous On Replace Control Continuous Off Check Power 2 Flashes * External Lockout 3 Flashes Inducer / Pr. Switch Error 4 Flashes Open Thermal Limit Switch 5 Flashes Flame Sensed w/o GV On 6 Flashes Ground, Polarity, Low Volts 7 Flashes Gas Valve Circuit Error 8 Flashes Low Flame Sense Signal 9 Flashes Open Igniter Improper Ground Low Voltage Faulty Triac More Than 10 Volts Between Neutral and Ground

10. SELF DIAGNOSTIC FEATURE CONTINUOUS ON - internal fault, or grounded sensor. Turn power off & on before replacing, may work OK. 2 FLASH - System lockout - no flame. See 3 FLASH - Pressure switch error. 4 FLASH - TCO (limit) open. 5 FLASH - Flame sensed with gas valve de-energized, (stuck open)


12. MICROAMP SIGNAL If you are getting call backs w/ two flash and have measured good ? amp signal check ground wire. MUST BE DIRECT FROM UNIT TO PANEL BOX. Also check burner closet to flame rod for good clean tight connection.


14. LOCKOUT - 2 FLASH A momentary loss of gas supply, flame blowout, or a shorted or open flame sensor will be sensed within .7 seconds during normal heating cycle. When a system lockout occurs, the IFC de-energizes the gas valve, energizes the inducer motor and indoor blower to heat speed.

15. Flame Sensing - Variables Remember Ohms Law E=I x R Watch that resistance Too little DC = too bad Too much AC = too bad Grounded flame sensor Look out for noise!

16. What happens in a circuit if resistance increases and voltage stays the same? What can affect the resistance in the circuit? What else can affect the flame signal? Flame Rectification Circuit

17. Increased Circuit Resistances Burner oxidation Non-secure burner Flame ?lift off? Loose wire connections Contaminated flame sensor Faulty grounds No grounds Reverse polarity

18. Question: Name something which can cause a ?2 flash? lockout which has not yet been discussed. While waiting for questions - cue up 3 flash videoWhile waiting for questions - cue up 3 flash video

19. Answer: 1) No gas available - check supply 2) Multiple recycles caused by other faults (ie: pressure switch trips) (See p.10) While waiting for questions - cue up 3 flash videoWhile waiting for questions - cue up 3 flash video

20. Fault Diagnostics - 3 FLASH Single Stage Bad vent system - improper draft, flue pipe or chimney blocked or plugged. Bad venter motor or fan dirty. Heat exchanger plugged or cracked. 90% units PVC not supported or pitched correctly back towards unit. ?? Maybe a bad pressure switch.?? A draft gauge or incline needed for testing.

21. Fault Diagnostic - 3 FLASH Two Stage and Variable Speed Blocked condensate drain 90% - 30 second off to drain condensate Inducer starts on hi speed then goes to low If 2nd stg PS after 3 min delay IFC restarts unit and run for 10 min. If 2nd stg PS still dose not close after 10 min IFC will start cycle again as long as there is a call for 2nd stage heat at thermostat.

22. 3 FLASH - cont. Variable Speed / TUY-R-A If 1st stg PS opens during 1st stg call for heat, gas valve is de-energized and inducer will go to hi speed for 10 min. If PS closes during 10 min the IFC will restart ignition sequence. If PS dose not close the inducer will be energized to hi again and continue cycle as long as 1st stg heat is calling. 2nd stg operation is same as page 12.

23. Fault Diagnostic - 4 FLASH Thermal Protection Devices Open TCO limit, aux.. limit, flame roll out, bad indoor blower motor, wrong motor speed, 90% units inducer limit (155?F open), burner box manual reset limit. If TCO is open check temperature rise through unit, check specs on unit label.

24. Fault Diagnostic-5 FLASH Flame sensed without a call for heat or when gas valve is de-energized. The IFC will energize indoor blower to run on heating speed. The system goes into lockout and will not be reset until this fault is corrected.

25. 50A55-571/-474 DIAGNOSTICS CNT02789 FIRST FOUR SAME 2-System lockout 3-Pressure switch 4-TCO open 5-Flame sensed Remember no LED and continuous on are code too THREE NEW CODES 6-115 Volt power reversed (MOVED FROM 2 FLASH) 7-Gas valve circuit error 8-Low flame signal

26. 50A50 & 50A55 Sequence of Operation Note 50A50 numbers after dash i.e.= -405 which I.D.?s specific IFC operation. Read text and follow the circled numbers on wiring schematic on page 15 to step through control operation. Note: Never jumper our pressure switches when trying to start unit. Our PS are all normally open at start up.

27. Two Stage 50A51 Sequence of Operation Note dash numbers Follow circled numbers again Remember on 1st stg call on heat inducer goes to hi on start up, then to low after 1st stage pressure switch closes. All IFC?s on call for heat do a self check to confirm TCO, aux.. Limits, and fuse links are closed and PS contacts are open.

28. Two Stage 50A51/61 Vari. Speed Sequence of Operation Same information as last two slides Note: Y and YLO on terminal board, for single stage cooling use Y Remember on Variable Speed I R-BK has to be jumpered to get correct air flow for cooling. If you don?t you will only get 80% airflow You can verify if jumpered as red LED above BK will be on.

29. IFC Quick Reference YOU MUST HAVE: SERVICE TIPS Volt/OHM Meter with micro amp scale ?A Water Manometer Incline Manometer with a 0 - 2? range Dwyer #1227 good Pocket Thermometer IFC requires 1.0?A minimum flame signal 80&90% single stage 1.8-3.0 ? 80&90% two stage 1st stg 1.2-1.8 ?A ? 2nd stg 2.3-3.0?A ? A good procedure is to check ?A signal B4 cleaning and after

30. Radiant Sense Ignition Controls Radiant sense was used for a short time on TUE Trane units. The control system is no longer used. There are six different versions how to identify see pages 39-40. Page 41 shows sensor and correct position of hot surface ignitor. The rest of the pages are sequence of operation and wiring schematics. Use as needed.

31. Troubleshooting Procedures If the LED on the IFC is on continuously, the fault is internal to the IFC. To make sure, interrupt line voltage for a few seconds and then restore. If internal fault is indicated again, and flame sensor is not shorted to ground, replace control. Note caution on five flash fault.

32. Troubleshooting Procedures Flow charts for controls 50A50, 50A51, and 50A52. Page numbers are off by two, 49=51, 50=52, 51=53 etc. correct now. 50A50 flame sensor fault (2 flash) what chart and page do we go to?? Page 55, chart 5a - 5p Lets do it. Pages 51 - 64 flow charts.

33. Service/Review... Observe... Ask questions? Observe? Check Fault Codes... Check equipment / proper sequence of operation, etc... Proper tools!

34. Installation/Service (Review) Things We Need To Get Better At: Gathering Information from the consumer. Looking beyond the failure in front of us, why did it fail. Shit does not just happen! Running the system long enough to stabilize: Checking your temperature rise or subcooling and superheat. Remember - Over 50% of the electronic controls replaced, did not need to be replaced.

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