Final answer:
A cad-cell reading very high resistance during burner operation could be caused by dirtiness or sooting, wiring issues, insufficient primary air, or incorrect barometric damper settings, requiring maintenance by a qualified technician.
Step-by-step explanation:
If a technician finds that the cad-cell is reading a very high resistance while the burner is operating, the most likely causes include:
- Dirtiness or sooting of the cad-cell, which obstructs the cell's ability to detect light, leading to an incorrect high resistance reading.
- Problems with the wiring, such as damaged or deteriorated insulation on the orange and white wires, which could cause poor connections and faulty readings.
- Insufficient primary air can lead to incomplete combustion and soot formation, which can dirty the cad-cell and result in high resistance readings.
- Adjusting the barometric damper improperly can affect the combustion air flow, potentially causing sooting or operational problems with the burner that would affect the cad-cell readings.
Maintenance or troubleshooting to correct these issues should be carried out by a qualified technician to ensure safe and efficient operation of the burner system.