Spectrex SharpEye 40/40I, User Manual

Page: 66 / 85

SharpEye
TM
IR3 Flame Detector User Guide
66 General Instructions for Electrical Wiring
Table 26: Wiring Length in Feet/Meters
Number
of
Detectors
Recommended Wire Diameter (AWG)
Power
Supply
Range
(VDC)
24 18 16 14 - - 22 – 32
20 18 16 14 - - 22 – 32
16 20 18 16 14 - 22 – 32
12 20 18 16 14 - 20 – 32
8 20 18 16 14 - 20 – 32
4 and less 20 18 16 16 14 20 – 32
ft/m 164/50 328/100 492/150 656/200 820/240
Max. Length from Power Supply to Last
Detector
Calculation Formula
Use the following formula to calculate minimum wire gauge per wire length
between the power supply (controller) and the detector, considering the
number of detectors on the same power line, where:
L = Actual wire length between the detector and the power supply.
N = Number of detectors per loop.
R = Resistance of wire per 100m (see Table 26).
V = Voltage drop on the wire.
Calculate the voltage drop on the wire as follows:
V = 2L x R x N x 0.2A
100
20+V = Minimum required voltage of the power supply
0.2A is the maximum power consumption of the detector
For example,
If N=1 (1 detector in loop)
L=1000m
Wire size = 1.5mm² (see Table 25, the resistance per 100m for 1.5mm² is
1.4Ω)
You calculate the voltage drop in the wire as follows:
2 x 1000 x 1.4Ω x 1 x 0.2A = 5.6V
100
The minimum voltage of the power supply should be 20V + 5.6V = 25.6V
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