urmet domus 1067/024, Руководство по установке

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DS1067-063D
47
LBT20064
4.2.2 Sizing of the power supply cable
The gauge of the cables must be selected so that the voltage of the power supply to various devices is correct, for the
purpose of obtaining stability, efficiency, and immunity from disturbances.
The gauge must be calculated after having taken into account the most critical situation of the system power supply, which
is equal to a blackout and the back-up battery with only a minimal charge (10.5 Vdc). Under these conditions, when fully
charged, all the devices in the 1067/024, 1067/032A and 1067/052A systems must be guaranteed at least 9 Vdc.
IMPORTANT! Check that there is in any case the minimum voltage of the functioning of the other devices used,
like the IR detectors, actuators, and sirens, etc.. Some of these devices may require a power supply voltage of
over 9 Vdc (the power supply data and the tolerances allowed are reported in the technical specifications of the
various devices).
As a result,
The maximum voltage reduction admitted on cables is: 1.5 Vdc
or 0.75 V on the positive cable and 0.75 V on the negative cable.
The formula to calculate this is
V
CONTROL PANEL
= 2 x length x R
CABLE
x I
DEVICES
where
V
CONTROL PANEL
is the reduction in power in Volts
length is the length of the cable (single conductor),in metres
R
CABLE
is the resistance of the cable in ohm/m
I
DEVICES
is the maximum current absorbed by the devices in Amperes (a value that can be found on their
technical specifications)
The values of copper cable resistance are:
Cross section sq.mm
2
(*)
0,22 0,50 0,75 1,00 1,50
Resistance in Ohm/m
0,0795 0,0350 0,0233 0,0175 0,0117
(*) Standards require that the cross-section of the cable cannot be less than 0.1 mm
2
.
Table 5 - Copper wire resistance
In the case of a complex power supply network, with multiple branches, it is necessary to calculate each individual
stretch.