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What’s the Difference Between a “Normally Closed” and “Normally Open” Switch?

Q: What is a safety outlet switch?

An integral part of our Safety Outlets for appliance garages, the magnetic switch is a mechanism activated by the position of an appliance garage door. When the door changes position, the switch signals power to turn on or off, depending on the switch’s resting state (“normally open” vs “normally closed”, explained below).

Q: What does “Normally Open” vs “Normally Closed” mean?

First, let’s review these terms as they relate to general electricity. The terminology can be counterintuitive, so bear with us:

• Normally Open (NO): At the normal, resting state, the contacts are physically separated, meaning the circuit is broken, and current cannot flow.
  
  Example: A typical doorbell button. At rest (not pressed), the contacts are open → no current. Press it, the contacts close → current flows → ding dong.
• Normally Closed (NC): At the normal, resting state, the contacts are “closed” and touching, which completes the circuit, so the current can flow.
  
  Example: A refrigerator light switch. At rest (door closed, button pressed), the contacts are closed → no light. Open the door, the switch changes → contacts open, light comes on.
• 👉 TLDR;

• Normally Closed = magnet activates switch → circuit opens → power OFF
• Normally Open = magnet activates switch → circuit closes → power ON

Do I choose a “Normally Open” or “Normally Closed” switch?

The terminology discussed above translates exactly into how our switches work, as they describe the resting state of the switch.

• Normally Closed (NC): At rest, the circuit is closed, and power is ON. When the appliance garage door closes, the switch activates, turning power OFF.

• Choose NC to turn power OFF when a door is fully closed.

• Normally Open (NO): At rest, the circuit is open, and power is OFF. When the appliance garage door is open, the switch activates, turning power ON.

• Choose NO to turn power ON when a door is fully open.