Typical Mounting Detail Of Fire Alarm Detectors





These typical drawings show how to install smoke detectors and heat detectors used in Fire Alaram system on false ceiling. The installation shall be as per the relevant section in the contract specification and drawing has the following major points:

  1. Smoke detector mounted on false ceiling with the help of loop in box.
  2. Firetuff or equivalent cable run under the RCC slab clipped to the soffit. Cable size shall be 2 core 1.5 sq. mm copper.
  3. Cable has to be looped to the detector and tied as shown in the drawing.

Typical mounting detail for Fire Alarm Detectors (Smoke detectors, heat detectors)

Another typical drawing shows how the smoke detector installs on false ceiling

Here smoke detector has been installed on false ceiling and connected through a flexible conduit. MICC cable or GI conduit with Firetuff cable to be run inside GI conduit for surface wiring and if concealed wiring, PVC conduit and firetuff cable can be used as detailed in project specification.

Smoke detector installed on false ceiling

Typical Specification For Fire Alarm Detectors

All individual heat and smoke detectors shall be of the analogue addressable type and be LPC / UL approved. All detectors shall be designed to have high resistance to contamination and corrosion and shall include RFI screening and feed through connecting components to minimize the effect of radiated and conducted electrical interference. Screens shall be included to minimize the effect of small insects. All detectors shall incorporate an LED, clearly visible from the outside, to provide indication of alarm actuation.

The detectors shall be fixed to the installation by means of plug-in bases. The addressable base must incorporate all the circuitry required for communicating detector status to the panel. Addressable detectors and modules must be able to transmit to the panel a pre-set and unique identifier to detect unauthorized changes in the system configuration. It must be possible to connect and mix automatic detectors, manual call points and addressable modules within the same zone sub-division of an addressable loop.

All detector bases shall be equipped with built-in line disconnection switch to isolate the defective part if the detection line suffers short circuit. All equipment connected to the system addressable loops, either directly or via interfaces, shall be proofed against electrical noise, high frequency pulses and electromagnetic influences from other equipment.

The optical smoke detectors shall be capable of detecting visible combustion gases emanating from fires. The detectors sensing chamber shall be optimized to minimize the effect of dust deposits over a period of time.

The heat detectors shall be capable of detecting rapid rise in temperature and fixed absolute temperatures. The heat detectors shall employ two heat sensing elements with different thermal characteristics to provide a rate of rise dependent response. Each addressable device shall have a positive means of demonstrating that the unit is fully operational. This may typically be by a tell-tale easily visible LED, blinking when the device is addressed.

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