9
4
Fig 3
Detector Field of View Plot
The flame detector should be positioned at the perimeter of the room, pointing directly at the
anticipated flame or at the centre of the area to be protected. If the detector cannot ‘see’ the whole
of the area to be protected, one or more additional detectors may be required.
The flame detector is not affected by normal light sources but should be positioned so that sunlight
does not fall directly onto the viewing window.
Detector Window Contamination
It is important to keep the detector window clean and checks should be carried out at regular
intervals – determine locally according to the type and degree of contamination encountered – to
ensure optimal performance of the flame detector. Although the IR detectors can detect flames
when the window is contaminated, there may be a reduction of sensitivity as shown in Table 1.
Contamination
Typical percentage of
normal response
Water spray
75%
Steam
75%
Smoke
75%
Oil film
86%
Salt water film
86%
Dry salt deposits
86%
Table 1
IR Detector window contamination
UV/IR detectors are more susceptible to window contamination and must be kept clean.
Connection Information
Centre line of detector
0.4m² flame seen at 40m
0°
15°
30°
75°
-15°
-75°
-90°
0
25m
-45°
-60°
-30°
40m
90°
60°
45°
0.1m² flame seen at 25m
Detector
Fig 8
Basic 2 Wire Connection Diagram
The simplest method of connecting the flame detector is in a 2-wire configuration as shown above.
With a 24Vdc supply the current (
i
)
drawn by a detector/detectors can be monitored to determine the
detector status. The DIL switches within the detector can be set to produce different current values
(
i
)
to suit control systems.
Detector Supply Current
i
@ 24Vdc
DIL Switch Setting
Normal
Quiescent
Current
Alarm
(Fire)
Current
1
2
3
4
Comment
3mA
9mA
0
0
0
0
Lowest power configuration, RL1 only
4mA
20mA
0
0
1
0
For 4-20mA systems, no relays
8mA
14mA
1
1
1
0
Lowest power configuration & relays
8mA
20mA
1
1
0
1
For 4-20mA systems & relays
8mA
28mA
1
1
1
1
Fire
control
panels
Table 4
Detector Supply & Alarm Currents
If the detector supply current falls below the normal quiescent current consumption then a fault is
present. This could be simply an open circuit cable fault or a fault within the detector possibly due to
the detector being taken over its rated temperature.
Detectors can be connected in parallel increasing the overall quiescent current required. The alarm
current signal will remain the same with the additional quiescent current drawn from other detectors.
2
1
Control Unit
(Supplied by others)
Flame Detector
Single pair cable, also see note 1
i
+
+
24Vdc Normal
(Break supply to reset
if detector set to latch)
-
-
NOTE 1
Screened cable should be used with one end
of the screen connected to earth. Also care
should be taken not to run the detector cable
next to power cables.
