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Wiring a Yard

 

Greetings (again),
I've got a yard that is about three feet wide. It has a ladder at both ends and a single track arriving and leaving. The track bus follows under the arriving track. Since I want to keep my 24AWG track feeder wires as short as possible I'm thinking of splitting the track bus in two. At the other end of the yard, do I bring the two busses back together or do I put a snubber on one, terminating it? How do I now calculate the length of the bus? If the split section is 20 feet long and the length of the bus on either side of the yard is a total of 40 feet, do I calculate the bus length as 60 feet (the accepted maximum) or have I effectively created an 80 foot bus? Which raises a related question: What is the effect of branching the track bus? Is the total length equal to the sum of the branches? Or is it just the length of the longest run? Are several splits worse than only one or two?
Thanks for your help, my education is far from complete (even at my advance years).
As always,
Michael Boyle

Don Vollrath
 

Michael et al
If you are not providing isolated yard tracks with any power cut off switches then each track is merely another parallel path for the DCC power to flow.... just like that on the track rails. Don’t worry so much about the wiring underneath. Provide a single main DCC bus to follow the main/center layout of the yard tracks from end to end while continuing onto the mainlines. Use multiple 20 AWG track feeders to connect each yard track to the same DCC bus. (24 gauge is kinda small) solder rail joiners or provide track drops for each section of track. Allow for some rail expansion movement to prevent kinking.

Calculate DCC bus length as if it were a single conductor. Avoid forming it into a loop. Add an R/C snubber at the ‘open’ end far away from the booster.

DonV

Jerry Michels
 

Michael,this is a great question.  I believe the length of the longest run is the answer.  Parallel busses should not affect the available power.

Jerry Michels
Amarillo Railroad Museum

wirefordcc
 

This topic is a good time to let new readers know about the work I did on track feeder size.  The results are on my website at:

http://www.wiringfordcc.com/track_2.htm#a14

There you will find a table of feeder sizes and feeder lengths that I tested .  My objective was to determine if a booster would trip or not.  I can definitely say do not use feeder sizes and lengths that are in the orange or red zones as your booster will not reliably trip.  

No matter what, after installation, short your track with a metal tool or object aka "the quarter test" to make sure your booster trips reliably.  Perform this test at the farthest point on a section of track from which the feeder attaches.  If its not going to work, you want to find out now.

Allan Gartner
Wiring for DCC

 

Thank you,
But what about the second part of the questions? How do we calculate the length of a track bus?
-Michael

Don Vollrath
 

It’s not that critical. One direction only. Estimate from beginning to end or Use a tape measure. 

DonV

dsabourne
 

I use the following online calculator for my wire sizing needs.

David

http://wiresizecalculator.net/

Tim
 

For that situation, the most important thing is keeping things organized. Consistent color coding is vital. Then come up with a sensible approach and stick with it.

Tim Rumph
Lancaster, SC