Hochiki DRD-E - Manual (Page 7)

DRD-E Flame Detector Installation Manual Page 7 of 12
© 2010 Hochiki Europe (UK) Ltd
2-3-0-1376/ISS1/NOV10
3 Quantities and Positioning
The number of detectors required and their position depends on:
 the anticipated size of the flame
 the distance of the flame from the detector
 the angle of view of the flame detector
The DRD-E flame detector is designed to have a class 1 performance as defined in BS EN54-10 on the high
sensitivity setting. That is the ability to detect an n-heptane (yellow) fire of 0.1m² or methylated spirit (clear)
fire of 0.25m² at a distance of up to 25m within 30 seconds.
In fact, the DRD-E flame detector will detect fires at distances of up to 40 metres, but the flame size at such
distances needs to be proportionally greater in order to be sure of reliable detection. Thus the yellow
flickering flame that can be detected at 25m, provided that its size is not less than 0.1m², will have to be
0.4m² in order to be detected at 40metres.
In a rectangular room the distance from the flame detector to the fire is calculated by the formula:
Fig 3 : Calculation of distance from detector to flame