VESDA Sensepoint XCL – Large Bore Installation Manual
VESDA
8
www.xtralis.com
2.3
Power Cable Specification
VESDA Sensepoint XCL requires a power supply from the controller of specified supply voltage range in
section "1.7 Specifications". Ensure that a minimum supply voltage is measured at the VESDA Sensepoint
XCL, taking into account voltage drops due to cable resistance.
V+ detector
VESDA
Sensepoint
XCL
V detector
V- detector
V+ controller
V controller
V- controller
Controller
Field Cable (L)
The maximum loop resistance (R
loop max
) in the field cable is calculated as follows:
R
loop max
= (V
controller
− V
detector min
) ÷ I
detector max
I
detector max
= W
detector max
÷ V
detector min
Example:
The controller is supplying a nominal 24 V DC (V
controller
), and the minimum allowable voltage of VESDA
Sensepoint XCL is 11 V DC (V
detector min
). Therefore, the maximum allowable voltage drop across the cable
between the controller and the detector is V
controller
− V
detector min
= 13 V DC.
Power consumption of the detector is maximum 2.3 W (W
detector max
). The maximum current required to drive
the VESDA Sensepoint XCL at the minimum voltage is 2.3 W ÷ 11 V DC = 209.1 mA (I
detector max
). So the
maximum field cable loop resistance (R
loop max
) is 13 V DC ÷ 0.2091 = 62 Ω. Therefore, the maximum cable
length for any given cable type can be found by dividing the maximum allowable cable resistance per core by
the cable resistance provided by the cable manufacturer.
The following table shows the typical maximum cable distances for our example.
Cable size (cross
sectional areal)
Typical cable resistance Maximum cable length
(L)
0.5 mm
2
(20 AWG
1
)
36.8 Ω/km
842 m
1.0 mm
2
(17 AWG)
19.5 Ω/km
1589 m
1.5 mm
2
(16 AWG)
12.7 Ω/km
2440 m
2.0 mm
2
(14 AWG)
10.1 Ω/km
3069 m
2.5 mm
2
(13 AWG)
8.0 Ω/km
3875 m
2.4
Detector Module
Legend
1
Inhibit switch
2
Status indicator
3
UP button
4
DOWN button
5
Current sink/source
selection switch
6
Negative voltage output
7
Positive voltage output
1
Nearest equivalent.
Summary of Contents for VESDA Sensepoint XCL
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