DCC Power Wiring
Practical considerations and quick tips
by Richard Schumacher
For those who have a medium to large size layout, and
wish to use a tested recommendation for new wiring, I
offer the following:
1. The power bus and control bus need to be
physically separate under the layout (recommend 12-18
inches or more if possible). When they need to cross,
try to do so at right angles. Keep both away from any
household AC (110VAC) wiring as well.
2. Use "Ethernet" network cable (termed
"CAT3" or "CAT5" - Category 3 or
Category 5) for the control bus runs instead of the flat
"modular" phone cable. This has built-in
twists that shields from interference.
3. Make power bus runs with 12AWG stranded wire. This
is available from Home Depot, in a variety of insulation
colors, as 500 foot spools that they label as
"12AWG 19/W Type THHN or THWN." Stranded wire
bends, and pulls through holes, easier than solid. It is
also harder to damage than solid wire. For those
concerned about the "AC surface effect,"
stranded wire has more surface area (because it is made
up of multiple individual wires) than the same size
solid wire. If you have an extra-large layout, you may
want to use 10AWG stranded wire. You may want to loosely
twist the power bus wires together (a twist every 1-2
feet).
4. Make feeder drops from the track as short as
possible, 6-10 inches is a good standard. Use 22AWG or
20AWG solid pre-tinned wire. Solid wire, and especially
pre-tinned solid wire, is easiest to solder to rail. As
long as the length is kept this short, it will not cause
a significant voltage drop. Use rosin-core solder to
make the joints. 22AWG solid pre-tinned hookup wire is
available in 100 foot spools, in a variety of insulation
colors, from Wire Works, Box 443, Guilford CT 06437.
Local electronics or hobby shops may carry it (Gateway
Electronics in St. Louis does).
5. Connect a feeder to every piece of rail. If that
seems like too much work, connect a feeder at least
every 5-6 feet with code 83 or 100 rail, or every 3-4
feet with code 55 or 70 rail.
6. The most reliable connection between the power bus
and feeder drops would be to solder them together. I
have done a number of railroads this way, and recommend
against it as there is a much (much) faster, safer (no
more burned fingers or legs), and almost as reliable
method available. This is by using "3M Scotchlok
self-stripping electrical tap connectors." These
are available from electrical supply stores for
$.19-$.24 each in boxes of 100.
Connect the 12AWG stranded power bus (run) to the
rail feeder drops (tap) using the 3M Scotchlock 567
connector (p/n 054007-14887). This connector is
specifically designed to connect a bus run (12 or 10AWG
solid or stranded) to a feeder tap (18-14 AWG solid or
stranded). I, and a number of my modeling friends, have
had very good success connecting a 12AWG stranded bus to
the Wire Works 22AWG solid pre-tinned feeder with these
connectors (your success may vary by the brand of
20-22AWG wire you use). No stripping is necessary, the
connector clips over the power bus wire, and the feeder
slides into a hole. Crimping with a pair of heavy pliers
makes the connection. Closing the connector cover
insulates the connection.
If you need to connect two 12AWG bus wires together,
use the 3M Scotchlok 562 (p/n 054007-11032). It is
designed to connect two power runs, either 12AWG solid
or stranded or 10AWG stranded only. Note that
significantly more pressure is required to crimp this
connector correctly.
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