Fire Fighting Enterprises FIRERAY 2000 (Legacy) - Manual (Page 3)

Fireray 2000 Installation Guide 22318.00.R 25.08.05
3
Detector Positioning
It is important that the Fireray 2000 Detector is positioned correctly to minimise the detection time.
Experiments have shown that smoke from a fire does not rise directly upwards, but fans out or mushrooms due
to air currents and heat layering effects. The time to signal a fire condition depends on the location of the
Detector within the premises, the volume of smoke produced, construction of the roof, and ventilation
arrangements.
The maximum distance either side of the beam axis is found to be typically 7.5 metres for satisfactory detection
under flat ceilings.
Smoke layering, where smoke does not reach the ceiling level due to layers of static hot air is over come by
mounting the Detector at the recommended height below the ceiling of between 0.3 and 0.6 metres, bringing
the infrared beam below the heat layer and into the smoke layer.
However in all installations the national fire standards for that particular country must be consulted. If there is
any doubt on the correct mounting height, positioning may be determined by smoke tests.
Detector Positioning In Apex Of Sloping Ceiling
A ceiling is defined as sloping if the distance from the top of the apex to the intersection of the ceiling and
adjacent wall is greater than 0.6 metres (See fig. 1).
When a Detector is positioned in the apex of a ceiling (See fig. 2). The lateral beam distance covered (
Υ) can
be increased in relation to the angle of pitch (
Φ).
For Example:
If the pitch angle is 20 degrees the lateral coverage can be increased from 7.5 metres either side of the beam
(
Υ) to:
Υ = 7.5 + (7.5 x 20/100) metres
Υ = 9 metres
Therefore with a roof pitch of 20 degrees the lateral coverage can be increased from 7.5 metres either side of
the beam to 9 metres either side of the beam, but only for the beam positioned in the apex. All other
calculations remain the same.
This formula can be applied to pitch angles up to and including 25 degrees. Therefore the maximum increase in
lateral coverage can be:
Υ = 7.5 + (7.5 x 25/100) metres
Υ = 9.375 metres
Pitch angles over 25 degrees must use the maximum lateral figure of 9.375 metres either side of the beam.
Φ = Pitch angle
Χ
Slope if
Χ ≥ 0.6 Metres
Single Beam
15 m
MAX 15 m
MAX (0.5m
↔ 7.5m)
MAX
Multiple Beams
0.3m
↔ 0.6m
(0.5m
↔ 7.5m)
MAX
Υ Υ
Υ (Max) = 7.5 + (7.5 x Φ/100)
Fig 1 Fig 2