If a flow switch is used in a duct system that has a humidifier, the flow switch would be used to:

If a flow switch is used in a duct system that has a humidifier, the flow switch would be used to:

• A. Turn off the fan if the humidifier stops
• B. Turn off the humidifier if the fan stops
• C. Turn off the humidifier if the humidity becomes excessive
• D. Turn off the fan if the humidity becomes excessive

Answer: (B)

A flow switch in a duct with a humidifier is there to ensure moisture is added only when air is actually moving. If the air isn’t flowing, turning off the humidifier prevents moisture from being released into still air, which could cause water overflow, condensation in the duct, or mold growth. In this setup, the switch stops the humidifier whenever the supply fan stops, so humidification only occurs during actual ventilation. Humidifier control isn’t based on humidity level itself, and a flow switch doesn’t measure humidity, so it doesn’t shut off the humidifier for excessive moisture. It also isn’t intended to control the fan, so it wouldn’t be used to turn off the fan if humidity is high.

A flow switch in a duct with a humidifier is there to ensure moisture is added only when air is actually moving. If the air isn’t flowing, turning off the humidifier prevents moisture from being released into still air, which could cause water overflow, condensation in the duct, or mold growth. In this setup, the switch stops the humidifier whenever the supply fan stops, so humidification only occurs during actual ventilation.

Humidifier control isn’t based on humidity level itself, and a flow switch doesn’t measure humidity, so it doesn’t shut off the humidifier for excessive moisture. It also isn’t intended to control the fan, so it wouldn’t be used to turn off the fan if humidity is high.