Nittan ST-P-OM Conventional Optical Smoke Detector, EN54-7, 12-32V F02_82220

What this detector does

A smoke detector watches for smoke and signals the fire alarm panel when it finds it. This Nittan unit does so with a light beam inside a small chamber.

On a conventional system, detectors are wired in zones. The panel tells you which zone is in alarm, and you then find the device.

How it works

• Light scatter: in clean air the light misses its receiver. When smoke enters the chamber the light bounces off the particles and strikes the photodiode, a sensor that reacts to light.
• Threshold: the alarm condition is raised when a set threshold value is met.

Where to use it

Its strength is smouldering fires, which make the larger particles it is most sensitive to. That often makes optical detection a good fit for bedrooms, offices and escape routes, subject to the system design.

Avoid kitchens and steamy areas, where a heat detector is usually the better choice.

What the figures mean in practice

• 50µA and 50mA: the first is the small standby draw. The second is the alarm current, so check how many devices your zone and panel allow.
• Current limiting: external current limiting must be observed. Conventional panels normally provide this, but confirm it for yours.
• Depth: it stands 48mm from the ceiling with a UB-4 base, and other bases may differ.
• Temperature: the working range stops at – 10°C, so check cold stores and unheated buildings.

Installing it

• Screens: all loop cable screens are connected together but isolated from ground, and go to earth at the panel only.
• Remote indicator: the indicator connects beside the zone wiring, drawing 2mA.
• Testing: test each head with a proper smoke test tool once the zone is live, and never with a flame.

Planning your system

Allow a base for each head. The system also needs a conventional panel with spare zone capacity, and a sounder and call points to make it a complete alarm.

Read the guide to the commercial fire alarm system before ordering. The category of system sets how many detectors you need and where.

Standards explained

• EN54-7: the European standard for point smoke detectors. This detector is to the 2018 edition, with LPCB 1461.
• LPCB: the Loss Prevention Certification Board, an independent body that certifies fire and security products.
• IP42: the 4 means protection against solid objects over 1mm, and the 2 means protection against dripping water at a slight angle.
• UKCA and CPR: it has a certificate for each, the UK and European construction product marks.