How does a pressure switch detect airflow through a duct heater?

How does a pressure switch detect airflow through a duct heater?

• A. By measuring temperature differences
• B. By analyzing electrical input
• C. By measuring air pressure before and after the duct heater
• D. By monitoring humidity levels

Answer: (C)

A pressure switch detects airflow through a duct heater by measuring air pressure before and after the duct heater. This functionality is crucial in maintaining system efficiency and safety. When the air passes through the duct heater, it creates a pressure differential that the switch can sense. If the airflow is adequate, the pressure difference between the inlet and outlet will fall within a specific range that indicates proper operation. If there is insufficient airflow—perhaps due to a blockage or failure of the fan—this pressure differential will not be met, and the pressure switch will trigger a response, such as shutting down the heater to prevent overheating or other issues. Temperature differences, electrical input analysis, and humidity levels are not mechanisms by which a pressure switch operates in this context. These factors may play roles in other parts of HVAC systems, but they do not directly relate to how a pressure switch detects airflow specifically.

A pressure switch detects airflow through a duct heater by measuring air pressure before and after the duct heater. This functionality is crucial in maintaining system efficiency and safety.

When the air passes through the duct heater, it creates a pressure differential that the switch can sense. If the airflow is adequate, the pressure difference between the inlet and outlet will fall within a specific range that indicates proper operation. If there is insufficient airflow—perhaps due to a blockage or failure of the fan—this pressure differential will not be met, and the pressure switch will trigger a response, such as shutting down the heater to prevent overheating or other issues.

Temperature differences, electrical input analysis, and humidity levels are not mechanisms by which a pressure switch operates in this context. These factors may play roles in other parts of HVAC systems, but they do not directly relate to how a pressure switch detects airflow specifically.