Electromagnetic door holder

Operation and Components
– Consists of a strong electromagnet
– Usually attached to a wall or mounted in a floor pedestal enclosure
– Mechanism can be mounted near the floor, at the upper corner of the open door, or at any convenient height along the latch edge
– Steel plate attached to the door contacts the electromagnet when the door is fully opened
– Electric current energizes the electromagnet to attract and hold the steel plate

Fire Alarm Control
– Triggers the cut-off of electrical power to electromagnetic door holders
Door holders release, allowing doors to close automatically
– Commonly used in conjunction with fire alarm control panels, burglar alarm control panels, or emergency systems
– Ensures doors are closed in the event of a fire or emergency
– Different power sources used to keep doors open (12 VDC, 24 VDC, 24 VAC, 120 VAC, or 240 VAC)

Door Locking
– Magnetic attraction of electromagnetic door holders can be manually overpowered, allowing door to close
– Closed doors may or may not mechanically latch or lock
– Fire doors often do not lock to facilitate easy evacuation
– Security doors may close, latch, and lock to prevent unauthorized passage
– Sliding or overhead doors can also be secured using similar designs

– Electromagnetic door holders designed to be fail-safe
– Interference with operation, such as power failure, causes release of doors
– Some door holders equipped with spring-loaded pins to overcome remanent magnetism
– Spring-loaded pins push magnetic plate away from electromagnet when power is cut
– Reliability is crucial in life safety and security applications

Related Concepts
Electric strike: another type of door locking mechanism
– Provides secure access control for doors
– Works by electronically releasing the door latch or lock
– Often used in conjunction with electromagnetic door holdersSources: https://en.wikipedia.org/wiki/Electromagnetic_door_holder