Auxiliary Functions & Interfaces
Relay modules, door holder releases, elevator recall, waterflow switches, tamper switches, and sprinkler system interconnections.
- Explain the function of relay modules and door holder releases
- Describe elevator recall requirements and the Phase I recall sequence
- Identify waterflow switch and tamper switch signal types
- Explain HVAC shutdown requirements upon fire alarm activation
- Describe isolator module function on Class A SLC circuits
Lección 1
Relay Modules & Door Holder Releases
Relay Modules
Relay modules (also called control modules) are addressable output devices that the fire alarm panel uses to control auxiliary equipment. When the panel sends a command, the relay module activates its dry contacts, which in turn control external equipment.
Common relay module applications:
- Magnetic door holders - release fire doors on alarm
- Damper actuators - close fire/smoke dampers
- HVAC shutdown - stop air handling equipment
- Stairwell pressurization - activate pressurization fans
- Access control - unlock doors on alarm
Normally Open (NO) Relay
Default state: Contacts open
On activation: Contacts close
Use: Start fans, activate equipment
Normally Closed (NC) Relay
Default state: Contacts closed
On activation: Contacts open
Use: Release door holders, trip shunts
Magnetic Door Holders
Magnetic door holders keep fire-rated doors open during normal building operation. On fire alarm activation, the relay module de-energizes the magnet, releasing the door to close by gravity or spring closer. This is a fail-safe design - loss of power also releases the doors.
Fail-Safe Design
Door holders are wired so that loss of power releases the door. This ensures fire doors close even if the fire alarm system loses power. The exam tests this fail-safe concept frequently.
Relay modules provide addressable output control for auxiliary equipment. Magnetic door holders use a fail-safe design where loss of power releases the door. Common applications include door holders, dampers, HVAC shutdown, and access control.