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Refrigeration & Air Conditioning Mechanic Red Seal · Question

A building management system (BMS) for a commercial HVAC system indicates a high differential pressure across the coil of a rooftop unit's air handler. The outdoor air damper is functioning correctly. What is the most probable cause?

A high differential pressure across a coil in an air handler indicates restricted airflow. The most common and easily rectifiable cause is a dirty or clogged ai

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Question: A building management system (BMS) for a commercial HVAC system indicates a high differential pressure across the coil of a rooftop unit's air handler. The outdoor air damper is functioning correctly. What is the most probable cause?

Answer options:

  • An overcharged refrigerant system ✅ A dirty or clogged air filter
  • A failing compressor
  • A miscalibrated thermostat

Correct answer: A dirty or clogged air filter

Explanation: A high differential pressure across a coil in an air handler indicates restricted airflow. The most common and easily rectifiable cause is a dirty or clogged air filter, which impedes air movement.

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