On normal hardwired, short distance installations one should not have a problem using higher resistance cable, but with modular systems where multiple devices are connected on the same cable it is important to see if your cable can supply enough current to these devices.
Different makes, lengths and thickness will also affect the resistance of the cable.
When it comes to large scale applications where cable distance is above 50 meter, careful wiring and power planning will be required.
Perimeter beams and passives spanning around a property or boundary walls this method of calculations does apply.
Install it the first time correctly and you will have many years of hassle free maintenance.
1. Take one Core of your cable and measure the resistance in Ohms over 100m.
2. Compare the result with Table 2, to calculate maximum power consumption over a cable length
3. Add module(s) power consumption connected to length of cable from Table 1
4. Power consumption must not exceed maximum available consumption over a specific length
5. Total Power consumption on system must not exceed Maximum Available Power (700mA-Paradox panels)
Example:
Connected on a 40m Length of cable, 2 x ZX8 and 1 x RTX3
Resistance of 100m of Cable 18 ohms
18 ohms over 100m (line 8 of Table 2) Maximum Available current of 40m 104 mA
Power consumption for above load
2 x ZX8 @ 30mA = 60mA
1 x RTX3 @ 30mA = 30mA
Total Consumption on single Cable = 90mA
Current of Load on Cable length does not exceed Maximum Available current on cable length = CAN INSTALL, if greater additional double up or power supply will be required.
Remember that loose connections and bad joints will affect the current supply to your devices. Always add
10% more for consumption to allow for variants. Don’t do these calculations and then add more devices on
the same cable afterwards.
Doubling up on strands will double the current a cable can supply. Adding a power supply module closer to
modules would also help. Mylar (screened) cable is recommended for industrial noisy environments.