- Slides: 28
Service/Review. . . Rule # 1: Use the KISS Principle!
Service/Review. . . Rule # 1: Keep It Simple Stupid
Start with the BASICS! n n 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 thermostat. Cycle it on the safeties. Drop out a motor.
Start with the BASICS! (con”t) Wiggle wires, jiggle connections and look everywhere. n Ignore your urges, remember that the last guy did what you’re considering and look how productive that was. n What are you looking for? - Won’t know until you find it! n
SELF DIAGNOSTIC FEATURE n n n 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/PS 1 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. (Red Book-Page 9)
SELF DIAGNOSTIC n n n 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. (Red Book-Page 9)
SELF DIAGNOSTIC SERVICE CALL n 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 W 4, series furnaces) n Note LED flash rate timing. n (Red Book-Page 9)
Diagnostic Code Label h h h Flashing Slow one/ sec Flashing Fast two/sec Continuous On Continuous Off 2 Flashes * 3 Flashes 4 Flashes 5 Flashes 6 Flashes 7 Flashes 8 Flashes 9 Flashes H Normal, No Call for Heat Replace Control Check Power External Lockout Inducer / Pr. Switch Error Open Thermal Limit Switch Flame Sensed w/o GV On Ground, Polarity, Low Volts Gas Valve Circuit Error Low Flame Sense Signal Open Igniter Improper Ground Low Voltage Faulty Triac More Than 10 Volts Between Neutral and Ground Flash Rate 1/4 sec on and 1/4 sec off, with 2 sec Pause Between Groups of Flashes
SELF DIAGNOSTIC FEATURE n n n CONTINUOUS ON - internal fault, or grounded sensor. Turn power off & on before replacing, may work OK. 2 FLASH - System lockout - no flame. See 1 3 FLASH - Pressure switch error. 4 FLASH - TCO (limit) open. 5 FLASH - Flame sensed with gas valve deenergized, (stuck open) (Red Book-Page 9)
Fault Diagnostics - 2 FLASH System lockout (loss of flame) n n n n BAD GROUND (power) LOOSE GROUND (wire or burner) WRONG GAS PRESSURE BAD HOT SURFACE IGNITOR DIRTY SENSOR BAD SENSOR NO GAS n n n CHECK ALL CONNECTIONS SET WITH WATER MANOMETER OHM OUT REPLACE IF BAD CHECK amp SIGNAL REPL. IF BAD GAS SUPPLY, SHUT OFF, GAS VALVE (Red Book-Page 11)
MICROAMP SIGNAL n If you are getting call backs w/ two flash n n 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.
MICRO AMP METER HOOK UP METER IN SERIES (Red Book-Page 25)
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. n When a system lockout occurs, the IFC de-energizes the gas valve, energizes the inducer motor and indoor blower to heat speed. n (Red Book-Page 11)
Flame Sensing - Variables Remember Ohms Law E=I x R n Watch that resistance n Too little DC = too bad n Too much AC = too bad n Grounded flame sensor n Look out for noise! n
Increased Circuit Resistances n n n n Burner oxidation Non-secure burner Flame “lift off” Loose wire connections Contaminated flame sensor Faulty grounds No grounds Reverse polarity
Fault Diagnostics - 3 FLASH Single Stage n n n 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. (Red Book-Page 11)
Fault Diagnostic - 3 FLASH Two Stage and Variable Speed n n Blocked condensate drain 90% - 30 second off to drain condensate Inducer starts on hi speed then goes to low If 2 nd stg PS after 3 min delay IFC restarts unit and run for 10 min. If 2 nd stg PS still dose not close after 10 min IFC will start cycle again as long as there is a call for 2 nd stage heat at thermostat. (Red Book-Page 12)
3 FLASH - cont. Variable Speed / TUY-R-A n n If 1 st stg PS opens during 1 st 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 1 st stg heat is calling. 2 nd stg operation is same as page 12. (Red Book-Page 13)
Fault Diagnostic - 4 FLASH n n n 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. (Red Book-Page 13)
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. n The system goes into lockout and will not be reset until this fault is corrected. n (Red Book-Page 13)
IFC Quick Reference n n n 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 n n n IFC requires 1. 0 A minimum flame signal 80&90% single stage 1. 8 -3. 0 80&90% two stage 1 st stg 1. 2 -1. 8 A 2 nd stg 2. 3 -3. 0 A A good procedure is to check A signal B 4 cleaning and after (Red Book-Page 20)
Radiant Sense Ignition Controls n n n 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. (Red Book-Pages 39 -49)
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. n Note caution on five flash fault. n (Red Book-Page 50)
Troubleshooting Procedures n n n Flow charts for controls 50 A 50, 50 A 51, and 50 A 52. Page numbers are off by two, 49=51, 50=52, 51=53 etc. correct now. 50 A 50 flame sensor fault (2 flash) what chart and page do we go to? ? Page 55, chart 5 a - 5 p Lets do it. Pages 51 - 64 flow charts. (Red Book-Page 50)
Service/Review. . . Observe. . . n Ask questions… n Observe… n Check Fault Codes. . . n Check equipment / proper sequence of operation, etc. . . n Proper tools! n
Installation/Service (Review) n n n 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.
Sample Service Ticket. WHAT’S WRONG?