Section 7
Low Airflow Fault
• This means the Carel controller told the VFDs to run, and the VFDs proved they were running, but the Carel controller didn’t receive a signal proving that the air pressure across the burner profile was high enough (.5” w.c. to .7” w.c.)
Causes for low air pressure drop • Clogged inlet filters • Loose drive belt • Blower rotating backwards – the blower will still move up to 60% of its capacity while rotating backwards • More external static (ductwork/transitions/turns) than what was expected when the unit was ordered • System effect – duct components installed too close to blower discharge • Profile opening around burner increased from factory setting • Leak in sensing tubes or switch diaphragm • Static probe location has been changed • Sensing tubes plugged • Blower speed reduced
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