Apollo Series 65 Optical Smoke Detector with Flashing LED 55000-316APO

What this optical smoke detector does

This Apollo head watches for smoke inside a small chamber, rather than for heat or flame. It sits on a conventional circuit, where the panel reports the zone in alarm rather than the individual device.

It suits installers and maintainers adding to or replacing heads on an existing Series 65 installation, as well as new conventional systems.

How does scattered light detection work?

Inside the case is a light proof labyrinth holding an infrared LED and a photo-diode, a sensor that reacts to light. The LED sits at an obtuse angle to the diode, so in clear air no light falls directly on it.

• First reading: every three seconds the LED emits a burst of light, and smoke scatters a fraction of it onto the photo-diode.
• Confirmation: above a pre-set threshold the LED emits two further bursts two seconds apart. Only then does it signal an alarm.
• Signalling: the detector increases the current it draws, and the control panel recognises this as an alarm signal. This is how a conventional circuit works.

Where to use it

It is rated Moderate/Good on smouldering fires and Very Good on overheating, but Poor on flaming clean burning fires. That makes the likely fire in the room the first question to ask.

Its IP23D rating and -20°C to +60°C range describe the conditions it can work in. Avoid dusty or steamy rooms, where an optical head can false-alarm.

What the figures mean in practice

• Sensitivity: 0.15 dB/m is a measure of how much smoke dims the light before the head alarms. A lower number would be more sensitive.
• Alarm current: the 52 mA at 24 V matters when you check how many heads could be in alarm at once on a circuit.
• Holding the alarm: in alarm conditions the supply may fall to 6 V dc if it can still give at least 10 mA at that voltage.

Planning your system

The height and weight with base show this head is designed to sit on one. Heads are normally sold without a base, so allow a compatible mounting base for each position.

A remote indicator connects through the -R terminal, which is limited to 17 mA. Check any current approval against your specification.

Standards explained

• EN 54-7: the standard for point smoke detectors.
• IP23D: IP ratings describe protection against solid objects and water. The first digit covers objects, the second water, and the letter D is an extra level for access by a wire.