A control system for a pump station uses a float switch to activate a pump motor. The float switch has a Normally Open (NO) and a Normally Closed (NC) contact. The control logic requires the pump to start when the water level rises to a certain point (activating the float switch) and stop when the water level drops (de-activating the float switch). Which contact configuration should be used?

Question: A control system for a pump station uses a float switch to activate a pump motor. The float switch has a Normally Open (NO) and a Normally Closed (NC) contact. The control logic requires the pump to start when the water level rises to a certain point (activating the float switch) and stop when the water level drops (de-activating the float switch). Which contact configuration should be used?

Answer options: ✅ The NO contact to energize the pump starter coil directly.

• The NC contact to energize the pump starter coil directly.
• The NO contact in series with a stop pushbutton, connected to a latching relay that controls the pump starter.
• The NC contact in series with a start pushbutton, connected to the pump starter coil.

Correct answer: The NO contact to energize the pump starter coil directly.

Explanation: If the pump needs to start when the water level rises and activates the float switch, the Normally Open (NO) contact is the most straightforward choice. When the water level rises, the float switch closes its NO contact, completing the circuit to energize the pump starter coil. When the water level drops, the float switch de-activates, its NO contact opens, and the pump stops. This is simple two-wire control.