Echelon DM-21 Device Manager - Manual (Page 24)

3-4 Network Cabling and Base Plate Installation
Power Cabling
It is important to note that a maximum of 16 Amperes RMS at 24VAC RMS can
be passed through the internal jumpers on the Power terminals of Type 1 Base
Plates. This means that if power wiring is looped in and out of the power
terminals of the Base Plates, the current load presented by all of the modules and
any other devices powered by that circuit must be <16 Amperes, as shown in
figure 3.6. If >16 Amperes must be supplied then the loop-through capability of
the Base Plate power terminals must not be used and the power cabling should
be run in parallel, as shown in figure 3.7. To calculate the load current, divide
the total VA (sum of all devices powered by the power supply) by the power
supply voltage. For example, if the total VA of all devices equals 100VA, and the
power supply provides 24 VAC, then the load current is 4.16A.
24VAC Supply
Base
Plate Base
Plate Base
Plate Base
Plate
Figure 3.6 Looped-through Power Wiring - ≤ 16 Amperes at 24VAC
24VAC Supply
Base
Plate Base
Plate Base
Plate Base
Plate
Figure 3.7 Parallel Power Wiring - >16 Amperes at 24VAC
As a rule of thumb, it is recommended that power and I/O cabling be separated by
18” (46cm) to prevent inadvertent pick-up of noise from the power circuit by
sensitive analog I/O cabling. Power and network twisted pairs may be combined
in a common cable if using an approved network cable.
The tables below present the wire gauge that should be used in order to deliver
the specified power (total VA) across the distance shown. These tables only
include wire gauges from 24AWG (0.5mm) to 12AWG (2mm) as these are the wire
gauges supported by the Type 1 and Type 2 Base Plate screw terminals. For the
supply cabling use at least 24AWG/0.5mm, 90° C rated wire.