Re: DCC Bus Wiring

Mark Gurries

I, I am a member of a Model Railway Club, here in Christchurch New Zealand. At long last the club has taken the first step in getting the layout ready for DCC. The layout is a double track continuous run of about 100ft on each track.
I have not seen the track diagram, but you indicated you have 100Ft loops of track. You did not say If the loop of track is stacked on top of each other or a big flat run around the room.

When you run any DCC bus longer than 30Ft, there are some considerations in the wiring.

Slitting the bus runs into two 30ft runs in each direction will allow you cover 60ft. This is discussed in the above section.

If you had 100Ft of track run in a double layer with 50ft on the lower level and 50 ft on the upper level, it become possible for a single booster to cover both levels.

But if you had 100ft flat layout, then it would be best advised to break the layout into to two booster districts. One booster cover 1/2 the layout while the 2nd cover the other half.

The question arose as to whether the buses could be continuous or would they have to be terminate so that the boosters fed out in each direct from where they were situated.
On Jul 7, 2015, at 9:11 AM, 'Vollrath, Don' [WiringForDCC] <> wrote:

Douglas, If your question is “Should the DCC bus be a continuous loop around the layout or be discontinuous ½ way around from the booster location”, you will get a mix of answers and arguments. Obviously the track may/can make a continuous loop without causing problems. I suggest that you make the DCC bus go around the layout in a continuous loop, with the attachment of the booster as a short ‘stub’ feeding the under the layout DCC bus. Add track feeders or ‘droppers’ as necessary around the layout. If you later notice DCC control problems in certain parts of the layout, Add an R-C snubber to the DCC bus supply loop ½ way around from the booster. If that does not resolve the DCC control issue, then cut the DCC bus into two pieces approximately equal length ½ way around the loop and add an R-C snubber to each lose end.
And add two insulated rail joiner above the location where you cut the bus in half so there is a 100% electrical break.

I can say from first hand experience, breaking the loop and wiring solved problems. I had a modular layout with a problem,

However if you address the 100ft bus run problem above, typically you will have broken the track electrically some place anyway negating concern for this issue.

Best Regards,

Mark Gurries
Electrical Engineer
DCC Website & NMRA DCC Clinics:

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