How Do Plunger Switches Work?

Plunger switches work by being pressed inward when a door is closed. When the door is opened, the plunger switch will pop up. The sensor will then know to alert the system and let it know that the door has been opened. Once the door is closed, the plunger switch will be pressed back down.

A plunger switch can only be used on a recessed door contact. This type of contact is inserted into the door and its frame so that it cannot be visibly seen from the outside. It should not be confused with a surface-mount door contact, which is placed on the outside of the door and its frame. Unlike a recessed contact, a surface-mount contact will be clearly visible from the outside of the door.

Most door contacts, whether they are recessed or surface-mount, operate using a sensor and a magnet. The sensor is installed on or inside the door's frame. The magnet is installed on or inside the door itself, usually within a half-inch of the magnet. When the door is opened, the magnet will separate from the sensor. This will cause a reed switch inside the sensor to activate. The sensor will then send an alert to the alarm system to let it know that the door has been opened.

But a recessed door contact with a plunger switch will not have a corresponding magnet or an internal reed switch. It will just be a sensor and a plunger switch. The sensor will be installed inside the door or the frame next to the door opening. Normally, the door will be closed, and the plunger switch will be pressed down. By opening the door, the plunger switch will be released and pop up. The sensor will send an alert when this happens to let the system know about the opened door.

Plunger switch contacts are relatively less common than door and window contacts that utilize a sensor and a magnet. Both hardwired and wireless plunger switch contacts are available. One type of wireless plunger switch contact is the Honeywell 5800RPS. This is a 345 MHz wireless sensor from the Honeywell 5800 Series that will work with most Honeywell Systems.