# DCC 5 Amp bus wire guage and type



## johnfm3 (Sep 30, 2016)

I am rebuilding a layout from the 1980s and updating to DCC. When I bought the layout, it came with dual dc controllers with switches and 6 track segments.

Since going to dcc, its my plan to remove the switches as they are a point for power loss. The other thing I have noticed is that the sound dcc controllers seem to drop early when multiple loco's are running. The wiring looks to be old 16 or 18 gauge. Similar to which was used for the old dual coil switch motors. I do believe its a stranded wire. Many say that 18 gauge can run 10amps low voltage.

What seems to be the norm for bus wire gauge when running a 5 amp layout? I will be keeping my layout segmented, just with out switches. And each segment will have a couple of power feeder wires of 20 or 22 gauge solid core wire.

The other question I have is the type of wire I am thinking of using. I am looking at fine stranded tinned copper wire. As current flows on the outer layer of each wire strand, I believe this should give the best possible chance of power transfer to each segment. Is there any reason to not use tinned copper wire?

John


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## CTValleyRR (Jul 26, 2014)

So let me make sure were using the same terminology. By "Track segment," I believe you are referring to a section of track that is electrically isolated from its neighbors. Most model railroaders refer to this as a "block". "Switches" refers to the electrical kind, which in this case presumably allow the user to independently reverse polarity of the rails in each block. As you seem to understand, these switches are unnecessary in DCC, where the decoder inside the locomotive determines the correct polarity to sedd to the motor. The only exception to this would be if you have a reversing loop -- a place where your train can leave a turnout traveling in one direction, and end up traveling back through that same turnout in the opposite direction. This requires an isolated section of track with all feeders to that track going through a special reverse loop controller, which is the same principle as the manual switches, but infinitely faster, and not requiring human intervention. The blocks will certainly work in DCC. Best practice is to wire each with its own circuit breaker to keep a short in one from shutting down the whole layout. 

You say "sound DCC controllers seem to drop off early...." I'mm not sure how to translate that. The controller is normally the DCC unit itself. The part in the loco is s decoder. Only decoders are "sound" or "motor and functions only"; the controller doesn't care which. Does " drops off" refer to speed, sound volume, both? Or is it stalling? Or the sound cuts out for a few seconds? 

First thing you want to do is clean your track thoroughly. This will eliminate dirty rails as a source of the problem. If your rails are brass or steel, you will need to clean them every couple of days. Otherwise, you have a power issue somewhere. Second question is how many locos are you trying to run at the same time? Each sound loco will draw half an amp or so when actually running, less if it's just sitting there with lights and sound on. If you're exceeeding the current output of your system, that would cause the problem. The solution to that is to add boosters to one or more blocks. 

Wiring itself doesn't sound like the problem, provided you have adequate feeders. The one thing you don't mention is how big your layout is. If you have long blocks with only a single pair of feeders, definitely add more. I would say track feeders every 6-8 feet is plenty; others recommend adding more. Bus guage may be a little light if you have a huge layout covering a couple hundred square feet, but stranded wire is certainly fine. Not sure about the tinned wire -- someone who knows more about electricity than I do can address that. Test your bus at the farthest points from the source. Do you have significant voltage drop (DCC should be about 14 volts, measured on the AC setting)? If so, a larger gauge bus may help. If your feeders are short (a couple of inches), 20 or 22 gauge is fine.

Hope that helps.


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## flyboy2610 (Jan 20, 2010)

For the bus wire itself I would 12 to 14 gauge wire. 16 gauge if the layout is small. There's really not a great price difference in wire gauges, and voltage drop is lessened with larger wire. For my current 19 x 7 layout I'm using 12 gauge for the bus. That way I know it's more than adequate.


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## mesenteria (Oct 29, 2015)

Amperage, the danger part of 'current', is more problematic the LOWER the voltage. For one thing, amperage makes the 'work', and is what the motor draws from the voltage. 

Work means heat. You want as little amperage as possible whenever possible for as long as possible. In the confined spaces in our small model shells, heat is a problem if you're making your decoders throughput a lot of amperage. Decoders will, and often do, run warm-to-hot, depending on their design, condition, and circumstances of installation.

If you are losing power at 'turnouts' (or do you really mean toggle or other types of switches....not clear on that), you might have problems along the points rails, where they mate to the closure rails, dirty tracks, or the turnouts are not mechanically and cleanly connected to their entrance rails. If you do mean toggles and switches, then by all means get rid of them if you're going to run DCC...they're redundant for anything except isolating tracks from the power grid if you don't want decoders sapping power and doing nothing but making annoying 'neutral' sounds.

For 5 amps, I would not run less thickness than 16 gauge on a power bus longer than maybe 15 feet. I use household 14 gauge wire, the kind you'll find servicing your outlets, and have bus runs exceeding 20' with not voltage loss that is appreciable. If you have heavier left over from a project, sure, why not use it. It'll be stiff, but suitable.

Remember, your own rails may run that long without needing more than one or two pairs of feeders at intervals. 12 gauge copper, and on down to 16 gauge, will do much better than your rails will.

If you keep feeders short, really short, you could get away with even 26 gauge wire. The problem comes with getting 5 amps through them when you get a hard short (your locomotive derails and shorts the two rails). If your rails are properly wired, your DCC system will immediately detect a hard short and cut track power to save itself and your expensive decoders. If you don't have good power distribution, and run long thin feeders only once or twice across an entire medium sized layout, those wires will get instantly very hot when the short happens if they are feeding the current nearest the short. So, the idea is to feed fairly often, say every 6 feet, and to keep the feeders to less than 18" if possible. If you simply have to go longer, go up to 20 gauge wire for security. Otherwise, I have only ever used the 22 gauge wire bundle with the white plastic sheath and four wires, yellow, green, red, and blue. Helps with colour coding your feeders to ensure the 'outer' rail always gets the black, say, and your inner rails get any other colour.

Stranded or monofilamental, your choice. What do you want to work with? I use the single strand for the bus and for the feeders. Some dislike the look or feel of the heavy bus wire and will use stranded. Almost nobody uses stranded for the feeders. For one thing, you can flatten the bared end of solid filamental copper and insert it into the joiners where you're likely to also solder for integrity and power reliability.


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## johnfm3 (Sep 30, 2016)

Is there any problem with the tinned copper stranded wire that I am considering using? Its a fine thread which means more strands, which also equates to better transmission of power.


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## DonR (Oct 18, 2012)

John

You have a lot of good advice in the above posts.

Most 'off the shelf' DCC controllers have a 1.5 or
so current rating. That is fine for 3 or 4 non sound
locos running at the same time. But if you have
SOUND locos it may not be enuf and you would need
to add a 5 amp booster. 

Does the 'old' DC layout have a bus wire to which
are connected track drops every 6 feet or so? If
so, that should be sufficient. If not, you should
install one. In addition, simply add the track
drops from the isolated 'blocks' to it, bypassing all
wiring to panel switches.

I prefer stranded wires, they are less likely to
break and cause problems. What you suggest
seems correct for what you want to do.

Don


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## johnfm3 (Sep 30, 2016)

DonR said:


> I prefer stranded wires, they are less likely to
> break and cause problems. What you suggest
> seems correct for what you want to do.
> 
> Don


Don,

The switches I have are like these (2 of them)...
Atlas Switch

The Pos wire of DC controller 1 went to the upper feed, and the Pos wire of DC controller 2 went to the lower. The output of the switch went to different segments of the layout. (Keep in mind for example I have two 18in length of track that are isolated ~ 2 out of 6) My segements are about 8 to 10 linear feet of track at most and 1 side track (not including the two 18 in loading tracks stated earlier.

All the different isolated segments power feed home run to the switches. And the switches were used to select Cont01/OFF/Cont02.

I am removing the whole wiring system and running new wiring to current standards for DCC.

Based on the responses, I will run a 14gauge bus wire. What about the tinned stranded copper vs normal stranded copper wire? Can anyone tell me the differences tinned vs non tinned stranded copper?

Thanks,
John


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## mesenteria (Oct 29, 2015)

There is no difference. Tinned means the solder running through and near the very tip strengthens and binds the strands. It's tidier, and if you intend to insert such an end into, say, the screwed and small orifice of input or output terminals on a device, say the rear of an amplifier, or into the front power module of my Digitrax DB150, it's just so much easier.


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## johnfm3 (Sep 30, 2016)

mesenteria said:


> There is no difference. Tinned means the solder running through and near the very tip strengthens and binds the strands. It's tidier, and if you intend to insert such an end into, say, the screwed and small orifice of input or output terminals on a device, say the rear of an amplifier, or into the front power module of my Digitrax DB150, it's just so much easier.


This is the wire I am looking at buying. Tinned in this case does not mean the end is soldered.
It may mean the wire is tin coated.... Not sure.


14 AWG Gauge Silicone Wire - Fine Strand Tinned Copper

John


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## deedub35 (Jan 29, 2014)

I think you are NOT making a wise decision buying this tinned wire at $9.99 for 10 feet.

You can buy normal stranded wire for $14.69 for 100 feet.



https://www.amazon.com/Southwire-55667123-Primary-14-Gauge-100-Feet/dp/B000PANY2G



There will be no noticeable difference in performance. It’s a model train layout - not a supercomputer.

You can buy 18 gauge for the feeders.



https://www.amazon.com/Southwire-55667423-Primary-18-Gauge-100-Feet/dp/B000HACYOS



Save your money on other things.


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## DonR (Oct 18, 2012)

John

You are wise to simply remove all of the old DC track power
wiring and switches. It would have been the source of
endless problems. The new track power bus fed by your
DCC controller and drops from the track every 6 feet or
so is all you need.
And I agree with Deedub's thought on saving $ on your
wire purchase. No need for expensive wires.
For connections of the track drops to the new bus many
of use use the 'suitcase' connectors available at most
Home Depot type stores.



'suitcase' electrical connectors - Google Search



They come in various sizes that accept the wire gauge
you will use. No wire stripping or soldering needed.
Makes your under table wiring much easier.

Don

Don


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## Lemonhawk (Sep 24, 2013)

That "14 AWG Gauge Silicone Wire - Fine Strand Tinned Copper " is expensive because its very flexible, great for places where the wire is connected to something moving -- like the heated bed of my 3d printer. Way to expensive to use as DCC bus wire. Also its only at high frequencies that the current runs on the surface of the wire so for DCC either stranded or solid works fine. I use 14 gauge stranded wire (Home Depot Automotive wire) for the power bus on my 5x7 layout and lots of screw terminal barriers with crimped lugs on the wire. Then 20 gauge stranded wire to the track from the bus (at terminal barrier strips). You could also look at Jameco's wire, lots of colors and gauges. That silicon wire is amazingly flexible so it would be kind of like using string (in terms of flexibility) so for a long run you would be constantly have to fasten it to something of it would droop all over.
Then there is the whole argument as to whether you should twist the DCC power bus wires to remove common mode errors (not worth arguing about) but do try to separate different DCC bus runs by an inch or two if you have several such as after DCC circuit breakers. Don't forget the quarter test after you done to check out the wiring!


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## johnfm3 (Sep 30, 2016)

So I am settling on the suggested 14 gauge stranded wire which was found on Amazon for the main bus. I am in the air on the drops whether I go with 18, 20, or 22 gauge solid core.

John


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## Lemonhawk (Sep 24, 2013)

I would pick 20, as long as the drops are less than 2 feet. You could use 22 if the drops were in the 6" category. easy on the solder - more on the flux.


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## mesenteria (Oct 29, 2015)

I service my mid-sized layout, a folded double main track of 60 feet, with eight feeder pairs of 22 gauge wire. One time, I serviced an off-layout staging yard accessed by a 6' length of splined roadbed with a single pair of 22 gauge feeders. If I performed a quarter test anywhere along the access spline or on the four track yard beyond it, I got instant shut-down by the short detection circuitry in my DB-150. So, 22 gauge wire will suffice for amperages of 5 or less over a distance of about 20 feet, and it will still permit the DCC system to detect a short when a quarter is placed across the rails.


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## johnfm3 (Sep 30, 2016)

mesenteria said:


> ...So, 22 gauge wire will suffice for amperages of 5 or less over a distance of about 20 feet, and it will still permit the DCC system to detect a short when a quarter is placed across the rails.





Lemonhawk said:


> I would pick 20, as long as the drops are less than 2 feet. You could use 22 if the drops were in the 6" category. easy on the solder - more on the flux.



Thank you to everyone. This is all good to know. I am going to keep my drops as close to under 1ft as possible. The Bus wire will more or less do a U shape around the layout board to keep the drops as close as possible. The controller will probably attach in the middle of the bus wire with no more than 10 feet each leg.

Just trying to minimize each electrical issue possible.

John


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## flyboy2610 (Jan 20, 2010)

Sounds like a good plan, John! You don't want your bus wire to be a loop, though. Just terminate it at the end with a wire nut so the wires can't accidentally short out.


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## johnfm3 (Sep 30, 2016)

flyboy2610 said:


> Sounds like a good plan, John! You don't want your bus wire to be a loop, though. Just terminate it at the end with a wire nut so the wires can't accidentally short out.


Correct, which is why I stated a U shape.


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## mesenteria (Oct 29, 2015)

I understood you, John, but there has been some debate over the 'shape' and length of buses for donkey's years on toy train fora. Sometimes it's just terminology, sometimes it's being up way past our bedtimes. We do get some newcomers asking if the bus wire ends need to be closed off with a snubber, or with marrettes, or just left dangling. Believe it or not, one common question is if the bus wires need to loop back and to be rejoined to the terminals. So, having an abundance of good will, we jump on that right quick and warn people to never tie the ends together, avoid long runs of closely parallel bus wires (if longer than about 20' in any one direction, helicize them a couple of times if they HAVE TO be close together for some reason), that it's seldom necessary to have snubbers at the ends, and that the wires are not to be looped back to their issuing point at the controller's output terminals.

You probably understand all this by now, but the better distributor is the thicker wire, and that makes the bus the ideal medium for getting range from the controller's outputs. The feeders should issue off of the bus whenever it is best suited to power the tracks above the bus. If the bus needs to be long, so be it. Too long, say much over 40' in one direction, you might have to start thinking about breaking the layout up into power districts and using 'boosters' to amplify the DCC signal. Buses that long start to experience voltage loss the same way long garden extension cords do.


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## johnfm3 (Sep 30, 2016)

mesenteria said:


> ...Too long, say much over 40' in one direction, you might have to start thinking about breaking the layout up into power districts and using 'boosters' to amplify the DCC signal. Buses that long start to experience voltage loss the same way long garden extension cords do.


This information is new to me. Thanks.

After the extension, the layout will be 13ft long and 7 ft wide. And I plan to have the bus wire more or less following the mainline of the layout.


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