What happens when the controller outputs 24V to a zone wire?

• A. The zone shuts off.
• B. The corresponding valve energizes.
• C. The common wire energizes.
• D. The controller resets.

Answer: (B)

When the controller sends 24V to a zone wire, it energizes that zone’s solenoid valve. Each valve has a 24V AC coil with one side connected to the zone wire and the other side to the common return. Applying voltage through the coil creates a magnetic field that pulls the valve’s plunger open, allowing water to flow to that zone. When the voltage is removed, the valve de-energizes and typically closes again. The common wire by itself doesn’t energize the valve, and a controller resetting is not part of normal operation.