What setup is needed to read all fan pressures accurately?

To accurately read all fan pressures, a comprehensive setup is essential, which is why the correct answer is that all the mentioned configurations are necessary.

A manometer measures pressure differences and can provide valuable information on how well a fan is performing. Each of the setups mentioned serves a specific purpose in measuring different aspects of pressure:

1. Hooking up a manometer to the side of the duct and connecting the other end to the atmosphere allows for measuring static pressure within the duct. This serves as a reference point and helps in assessing the static pressure losses due to friction and other factors within the ducting.

2. Attaching a manometer with one end to the side of the duct and the other inside the duct facing the airflow is crucial for measuring dynamic pressure or velocity pressure. This configuration helps determine the pressure exerted by the moving air within the ducting, which is important for understanding airflow dynamics and the fan's performance.

3. Positioning a manometer inside the duct facing the airflow with the other end open to the atmosphere measures the total pressure. This provides a complete picture by incorporating both static and dynamic pressures and allows for calculations that can relate to the efficiency and effectiveness of fan operation.

Having all three configurations allows a technician to gauge the total pressure