- Description
- Specifications
Flush-Mount Electromagnetic Door Holder with 33 lb Holding Force and Tri-Voltage Operation
The Seco-Larm DH-171SQ is a flush-mount magnetic door holder that delivers 33 pounds of holding force from a compact, recessed design. It operates on 12VDC, 24VDC/VAC, or 120VAC input, making it compatible with virtually any existing access control or fire alarm power supply. The cast aluminum faceplate and UL listing make it suitable for commercial and institutional installations where code compliance matters. It belongs to the broader security and access control category of door-holding devices designed for fire safety and access management.
The DH-171SQ is a fail-safe device, meaning it releases the door when power is lost. This is the standard configuration for fire door applications where doors must close automatically during a fire alarm or power outage. Built-in spike suppression circuitry protects the unit from voltage transients, and the adjustable armature plate accommodates variations in door-to-frame alignment during installation.
Where the DH-171SQ Fits
- Fire-rated door hold-open systems where the magnetic holder keeps fire doors open during normal operation and releases them automatically when the fire alarm panel cuts power, allowing the door closer to pull the door shut
- Commercial building access control where stairwell, corridor, or lobby doors need to stay open during business hours and release on alarm or at scheduled times through a connected access control system
- Retrofit installations with mixed voltages where the tri-voltage input (12/24VDC, 24VAC, or 120VAC) lets the DH-171SQ connect to whatever power source is already available at the door location
What the DH-171SQ Delivers
- 33 lb electromagnetic holding force: Sufficient for standard interior fire doors and stairwell doors. The flush-mount armature plate sits recessed in the door, creating a clean installation with no protruding hardware.
- Tri-voltage operation (12/24VDC, 24VAC, 120VAC): Connects directly to the most common power sources found in commercial buildings. No external transformer or voltage converter required in most installations.
- Fail-safe release: Door releases automatically on power loss or fire alarm activation. Meets fire code requirements for doors that must close during emergencies without manual intervention.
- UL Listed with spike suppression: UL listing confirms the unit meets safety standards for commercial installation. Built-in spike suppression circuitry protects against voltage transients from shared electrical circuits.
- Adjustable armature plate: Compensates for door-to-frame misalignment up to the adjustment range, reducing installation time and ensuring full contact between the magnet and armature for maximum holding force.
What Are Magnetic Door Holders Used For?
Magnetic door holders keep fire-rated and access-controlled doors in the open position during normal building operation. They connect to fire alarm panels or access control systems so the door releases and closes automatically during an emergency or at a scheduled time. In fire safety applications, building codes require that fire doors close when the alarm activates. A magnetic door holder satisfies this requirement by holding the door open with an electromagnet that releases instantly when power is cut. The Seco-Larm DH-171SQ is designed for this purpose, with fail-safe operation and UL listing for code-compliant installations in commercial, institutional, and multi-family residential buildings.
