# DC Wiring....Specifically bus and feeder question



## [email protected] (Apr 29, 2016)

Hello,
I'm bulding an HO layout which is simply a large dog bone design, which implies loops at each end of the dog bone. The loops are on benchwork that is 12'x5' with the connecting benches between the loops only being 30" deep but are approximately 80' long. Since I've got a double-track mainline, there are 4 tracks running through all of the 30" benchwork and 2 tracks running around the end loops.

I'm about to begin wiring, which is where I have several questions. I've got large spools of 14 gauge stranded wire for the busses left over from a previous layout and tons of 18 gauge solid wire for the track feeders. I'm wondering if I should run my busses down the middle of my 30" deep sections so that feeder wires from inside and outside tracks can attach to them, rather than running busses directly under each set of tracks. The idea is to limit the distance of my bus "runs". If I do this, then my 18 gauge feeder wires would have to be longer....maybe 24 inches or more to reach from outside tracks to the center bus wires. So, should I make the busses longer by having them run directly under each set of tracks and have the feeders only about 10" or do I go with the busses down the middle, requiring longer feeders?

Another question is whether I need to center my power packs on the layout. Unfortunately, I already mounted my two packs on a platform under the layout, near a wall outlet and don't want to move the platform if I don't need to and buy another surge protector with a longer cord. Based on where the platform is now, the run for my busses from the power packs to the loop on one side is about 40 feet and the run from the power packs to the other side of the layout is about 80 feet. Am I going to lose noticeable power at the end of the 80 foot run with 14 gauge wire? If you guys thinks so, then I will move the platform.

Thanks in advance for any help you can provide,
Mondo


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## Dennis461 (Jan 5, 2018)

*you worry too much*

Is that 80 feet or inches?
Can you post a sketch.

18 gauge wire is approximately 6.4 ohms per 1000 feet.
(http://www.ohmslawcalculator.com/awg-wire-chart)

If you run 2 feet feeders, each of the two conductors will be around 0.0128 OHMS.
Running a couple of locos, car lights, may draw 2 amps.
Voltage drop will be .0256 volts per feeder, or 0.0512 volts total.

Your solder connections are what you need to be concerned with.
I would recommend under layout terminal boards if you have trouble soldering.

Keep you connections close to the front so you can get at them for repair or alterations.


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## [email protected] (Apr 29, 2016)

Dennis461 said:


> Is that 80 feet or inches?
> Can you post a sketch.
> 
> 18 gauge wire is approximately 6.4 ohms per 1000 feet.
> ...


Hello Dennis,
Thank you for your reply!
To answer your question, it is 80 feet, not inches.

Using your calculation, where you said voltage drop per feeder will be .0512 volts, that if I go with feeders every 6 feet, as planned, and I have 240 feet of track, then I will have 40 pairs of feeders and my voltage drop will be 40 times .0512=2.048 volts. A 2 volt drop seems significant so I wonder if I should go with 1 foot feeders and cut the drop to only 1 volt? Of course, to go with the 1 foot feeders, I will have to double my buses by setting them under each pair of tracks.

You mentioned soldering connections. I plan to solder all feeders to the buses and I expect to solder my rail joiners also.

Thanks,
Mondo


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## Dennis461 (Jan 5, 2018)

No, I calculated the feeder voltage drop.
Assuming your feeder is connecting the 14 gauge bus to the rail, at each feeder location, the rail will be .0512 volts less than the bus voltage.

I'll post a sketch in a few minutes using 80'...

OK a few minutes has passed....
I would double up on the bus wire, use double 14 gauge if you've already got it, or move up to 12 gauge or even 10 gauge.

Again, this is with 2 amps draw, power supply at far right. the loop tables not included, but you get the idea. Also, this does not take credit for the rail, meaning the 2 amps will split between the bus and the rail, overall voltage drop will be lower but calculation can get complicated as the locomotive passes each feeder/drop.


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## [email protected] (Apr 29, 2016)

Dennis461 said:


> No, I calculated the feeder voltage drop.
> Assuming your feeder is connecting the 14 gauge bus to the rail, at each feeder location, the rail will be .0512 volts less than the bus voltage.
> 
> I'll post a sketch in a few minutes using 80'...
> ...


Dennis,
I don't get the math in your exhibit. You show that 15vdc minus .0512=14.544. When I do the subtraction, I get 15 minus .0512=14.9488. What am I doing wrong?

Bottom-line....I will center my power packs so that my buses from the power packs are each around 60 feet and I'll probably upgrade from 14 gauge wire to 12 gauge because so many threads I've read suggest that 14 gauge is good for "most" home layouts but 12 gauge is necessary for "club" size layouts, which mine really is.....even though my club is just me.

Thanks for your help,
Mondo


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## Dennis461 (Jan 5, 2018)

Good, you found one of my mistakes, seems like you understand the principle.
I corrected my diagram.

Let me guess, you live in a bowling alley basement?


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## jimben (Jun 27, 2018)

Run $12 or #14 wire as a center bus the length of track. I would use a track power connector every 8-10 feet. You can use as light as #20 gauge wire to feed the center bus wire from your controller and from center bus wire to track power terminals. Voltage drop would be insignificant and engines would not slow down anywhere on the track.


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