- Condition: The dryer has detected a temperature in the heating chamber lower than the under temp band setting on the Burner Settings screen for more than 5 minutes as allowed by the hard timer in the controller program.
- Alarm Action Taken: MINOR ALARM
- Component: RTD (Resistance Temperature Detector), Modulating motor & “Butterfly” valve
- Location: The sensor originates in the junction box up inside the dryer inside of the square ductwork mounted just inside the lower access door under the burner. The sensor runs outside the airduct into the heating chamber and is then ran vertically usually alongside of the internal access ladder in the heating chamber.
The modulating motor and butterfly valve are located on the fuel trane at the bottom of the dryer.
Tools Required for Service:
- Voltage/continuity meter (to check ohms & voltage)
- Small Phillips screwdriver (to loosen screws on mod motor lid)
- Wire strippers (if replacing sensor or refreshing connection)
- Replacement small wire nuts or crimp connectors
- 3/8” wrench or impact w/3/8” socket (to loosen p-clips if replacing RTD)
Tech tip: (RTD 1000 ohms @70 degrees device) (Modulating motor 115 vac input w/24 vac internal transformer)
The RTD used for this function is an “averaging” unit. It senses temperature along the entire length of the unit and sends back the “average” temperature readings/resistance to the controller.
Potential causes of this alarm condition:
- Too low of gas pressure from vapor regulator causing not enough gas volume to burner to achieve temperature setpoint with modulating motor and gas “butterfly” valve wide open
- Insufficient gas supply to dryer
- Faulty modulating motor
- “Butterfly” valve stuck or faulty
- Plugged burner
- Corroded/loose connection on RTD
- Faulty RTD