Specifications

Operations Manual, Redundant System Controllers 209351 REV B 63
Paradise Datacom control cables utilize 20 conductors of #18 AWG stranded wire. The
control cable schematic is shown in Figure 5-3. The resistance of #18 AWG stranded
wire is 6.5 ohms per 1000 feet. The controller switch connector (J3) allows contacts for
2 wires per switch connection. Therefore, two conductors can be paralleled for both the
source and return lines for the transfer switch. With a maximum allowable voltage drop
of 6 volts, this equates to a 3 volt drop in the source wires and 3 volt drop in the return
wires. This is shown schematically in Figure 5-3. Using four (4) parallel #18 AWG
conductors gives a resultant cable resistance of 1.6 ohms per 1000 feet, or 0.0016
ohms per foot.
To calculate the maximum cable length that can be accommodated to the transfer
switch, first consider the current draw by the switch either from the manufacturer’s data
or from Table 5-1. Next divide this current into 6 volts. This gives the maximum cable
resistance to and from the switch. Finally, divide this cable resistance by 0.0016 ohms/
ft. to find the maximum cable length. This is shown in the following example:
Switch Current draw = 3 Amps
6 V / 3 Amps = 2 ohms
2 ohms/1,250 ft. = 0.0016 ohms/ft.;
maximum cable length using (4) #18 AWG connectors
Table 5-2 gives the maximum cable length for some popular switches.
Figure 5-3: Cable Losses to Transfer Switch
SYSTEM CONTROLLER
DATACOM
PARADISE
RCP2-1200
1:2 REDUNDANT
Part Number Description Manufacturer Maximum Cable Length
75SBOS 10.7-14.5 GHz Waveguide/Coax Sector 4,690 ft. (1,430 m)
3NBGS 5.8-6.4 GHz Waveguide/Coax Sector 1,880 ft. (572 m)
2SBGS 3.7-4.2 GHz Waveguide/Coax Sector 1,250 ft. (381 m)
4BF 1.7-2.6 GHz Waveguide Sector 938 ft. (286 m)
Table 5-2: Maximum Cable Length for Selected Switches (Single Switch Systems)