What gauge wire to use...
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The answer is in Ohm's law.
#14 has 2.525 ohms per 1000 feet.
#12 has 1.588 ohms per 1000 feet.
A 10-foot loop (ten out ten back) of #14 would drop .051 volts per ampere.
A 10-foot loop of #12 would drop .032 volts per ampere.
The difference is inconsequential unless you run enough stuff to draw 10-20 amperes from the buss, or the buss is hundreds of feet long. I would think most voltage drop, even with #16 or #18, would be in the power supply and not the buss.
Tom
Dave: as I posted, either one will be sufficient to carry the amperage without a significant voltage drop difference. If you are concerned about how much current the two sizes can safely carry...don't. Both are way more than you will ever have on a layout (your house circuits are wired with 12awg). Our main concern with small vs. large awg is DC resistance. This is why many of us choose the larger size which always has less resistance.
My 1500+ ft track layout is all over a 24x40 garage with an additional room at 8x20. I use 12awg solid instead of 14awg, but mostly because I like to work with it. Also, I have very little voltage drop in the bus/feeds/track mostly because I parallel my bus to different parts instead of one continous series circuit and have my Super Chief 8 amp located in the middle of all of it.
Tom: you would have to flex a 12awg solid conductor many times before you could get it to break...many more flexes than any norm. Also, a few extra ohms resistance in the bus plus the feeds and track can add up to become problematic. It doesn't take but a decrease in a few volts to change the operating characteristics of a locomotive. Granted, the size layout would dictate which size bus is sufficient, but it never hurts to go with larger size wire for any layout..."overkill" or not.
Hi Rex,
I agree with you 100% (who could disagree?) that the problem for longer wire lengths is resistance.
I also agree about the difference between stranded and solid wire. My point was to dispell any myths a difference exists between solid and stranded so far as digital noise or voltage drop in the systems we are dealing with. The primary difference in this application is mechanical, not electrical.
I think putting a number on things is always best.
1.) #20 drops .2 volts per ampere per every ten feet of distance (20 feet conductor length) covered (this is why I only used #20 multiconductor cables for my short feeds in a yard where only one locomotive can possibly run)
2.) #18 drops .07 volts per ampere per every ten feet of distance (20 feet conductor length) covered
3.) #16 drops .08 volts per ampere per every ten feet of distance (20 feet conductor length) covered (This is why my main power and lighting buss, which is only 20 feet long (40 feet of loop resistance in any path), is number 16.
4.) #14 drops .051 volts per ampere per every ten feet of distance (20 feet conductor length) covered
5.) #12 drops .032 volts per ampere per every ten feet of distance (20 feet conductor length) covered
.....we can see what size is worthwhile. I mostly like to minimize wire size to safe limits to make things easier to work with.
Tom
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Cjcrescent
Master Mechanic
Feeders-20-22ga
Bus-12-14ga
Bus-12-14ga
Larry
Long Winded Old Fart
I have DC only & I run 14Ga. for Buss & 22 to 20ga. for drops. I ran stranded wire for Buss & solid for drops. I had a lot of stranded spools of wire, but, if I would have had solid copper I would have used that. Like Rex said, "Copper is a lot easier to solder to" for everything. I used up a whole(250ft)spool of each color(blk. & Wht.) on my layout.
I used up another spool of red & white solid copper 20ga.(250ft) for drops.
I used up another spool of red & white solid copper 20ga.(250ft) for drops.
hamltnblue
Active Member
It also depends on the size of the layout. If you're running a 4x8 you'd only need 16 or 18 gauge wire for the buss.
dpeterson3
Member
Soild wire will give better data rates. There is less noise in solid from electrons running into each other and jumping from wire to wire. Digitrax baud rates are so slow that this makes absolutely no difference, though. You can't tell a difference until data rates start getting into the Gigiabits/second range. As for bus wires, use Gauge 1 because you could handle a few thousand volts and make miles and miles of runs. I think I have a piece laying around. I might try that.
dp3, not sure what your point is. The use of a larger AWG wire, such as 12 or 14 is not just for their amperage rating, but more for their lower resistance. This is a negligible concern for a small, 4x8 layout, but the voltage drops can add-up on a large layout or any layout that runs many trains at once. Since price differences in size for our quantities is near nothing, a good rule of thumb is to go with the larger wire. Another easily learned fact: larger wire is a whole lot easier to work with.
dpeterson3
Member
I'm in school becoming an Electrical Engineer. The thought of using gauge 1 on a layout amused me enough that I posted it to see what people would say about it. Essentially, it falls under my weird sense of humor. Sorry if no one else appreciates it.
railBuilderDhd
Active Member
I was getting ready to wire a Free-Mo module and was thinking of getting 14 AWG wire for the bus but wanted to know if others think I should get 12 AWG since it's a large layout that I will be connecting to. We run Digitrax DCC system and the the layout can get rather long with all the modules connected. I have solid wire as I thought it would be better.
Dave
Dave
railBuilderDhd
Active Member
Rex,
I do want to keep the wires neat as you mentioned. I would like to know if you think 14AWG will be enough or should I get 12 AWG wires and not mess with the 14 AWG wire at all for the main bus?
Dave
I do want to keep the wires neat as you mentioned. I would like to know if you think 14AWG will be enough or should I get 12 AWG wires and not mess with the 14 AWG wire at all for the main bus?
Dave
There is no difference at all electrically, at the frequencies involved in systems like this, between solid and stranded. Absolutely none. This includes noise and propagation of any digital information.
Differences in noise are mostly due to conductor resistance (conductor cross section) and how conductors are laid against each other (twisted, parallel, or separated).
After measuring the current draw of my locomotives, I decided a #16 buss was overkill if I ever ran DCC or for multiple lights in buildings, and that normal CAT-3 and CAT-5 cables were more than good enough for signaling, turnouts, and detectors.
I chose a #16 four conductor buss, CAT-5 cables (four pairs) for power to a yard (10-15 feet away) where I sectionalized tracks to run my non-DCC equipment, and CAT3 cables (three pair like telco house wiring) for powering turnouts.
I have ribbon cable (16 conductors but very small) following the large buss under the main lines for signaling because it is easy to tap into.
For this application, the only difference between solid and stranded is physical. Solid forms better but breaks easier when flexed, while stranded bends easier and resists breaking. Solid is easier to keep under screws and terminals without tinning, but stranded works just as well if the strands are tinned into one conductor when fastened under screws.
Tom
Differences in noise are mostly due to conductor resistance (conductor cross section) and how conductors are laid against each other (twisted, parallel, or separated).
After measuring the current draw of my locomotives, I decided a #16 buss was overkill if I ever ran DCC or for multiple lights in buildings, and that normal CAT-3 and CAT-5 cables were more than good enough for signaling, turnouts, and detectors.
I chose a #16 four conductor buss, CAT-5 cables (four pairs) for power to a yard (10-15 feet away) where I sectionalized tracks to run my non-DCC equipment, and CAT3 cables (three pair like telco house wiring) for powering turnouts.
I have ribbon cable (16 conductors but very small) following the large buss under the main lines for signaling because it is easy to tap into.
For this application, the only difference between solid and stranded is physical. Solid forms better but breaks easier when flexed, while stranded bends easier and resists breaking. Solid is easier to keep under screws and terminals without tinning, but stranded works just as well if the strands are tinned into one conductor when fastened under screws.
Tom
The answer is in Ohm's law.
#14 has 2.525 ohms per 1000 feet.
#12 has 1.588 ohms per 1000 feet.
A 10-foot loop (ten out ten back) of #14 would drop .051 volts per ampere.
A 10-foot loop of #12 would drop .032 volts per ampere.
The difference is inconsequential unless you run enough stuff to draw 10-20 amperes from the buss, or the buss is hundreds of feet long. I would think most voltage drop, even with #16 or #18, would be in the power supply and not the buss.
Tom
Dave: as I posted, either one will be sufficient to carry the amperage without a significant voltage drop difference. If you are concerned about how much current the two sizes can safely carry...don't. Both are way more than you will ever have on a layout (your house circuits are wired with 12awg). Our main concern with small vs. large awg is DC resistance. This is why many of us choose the larger size which always has less resistance.
My 1500+ ft track layout is all over a 24x40 garage with an additional room at 8x20. I use 12awg solid instead of 14awg, but mostly because I like to work with it. Also, I have very little voltage drop in the bus/feeds/track mostly because I parallel my bus to different parts instead of one continous series circuit and have my Super Chief 8 amp located in the middle of all of it.
Tom: you would have to flex a 12awg solid conductor many times before you could get it to break...many more flexes than any norm. Also, a few extra ohms resistance in the bus plus the feeds and track can add up to become problematic. It doesn't take but a decrease in a few volts to change the operating characteristics of a locomotive. Granted, the size layout would dictate which size bus is sufficient, but it never hurts to go with larger size wire for any layout..."overkill" or not.
railBuilderDhd
Active Member
I'm thinking on a free-mo layout that could get rather large I'm better at running the 12AWG and using the 14AWG for the accessories bus line. My thinking for this is the fact that the layout could get rather long at train shows with us connecting with other groups (we will be doing this at the next show) and as a result of 2 free-mo group we may end up with a large number of locomotives running at one time. I would feel better knowing my modules are not going to be the weakest link in the chain.
Thanks,
Dave
Thanks,
Dave
Hi Rex,
I agree with you 100% (who could disagree?) that the problem for longer wire lengths is resistance.
I also agree about the difference between stranded and solid wire. My point was to dispell any myths a difference exists between solid and stranded so far as digital noise or voltage drop in the systems we are dealing with. The primary difference in this application is mechanical, not electrical.
I think putting a number on things is always best.
1.) #20 drops .2 volts per ampere per every ten feet of distance (20 feet conductor length) covered (this is why I only used #20 multiconductor cables for my short feeds in a yard where only one locomotive can possibly run)
2.) #18 drops .07 volts per ampere per every ten feet of distance (20 feet conductor length) covered
3.) #16 drops .08 volts per ampere per every ten feet of distance (20 feet conductor length) covered (This is why my main power and lighting buss, which is only 20 feet long (40 feet of loop resistance in any path), is number 16.
4.) #14 drops .051 volts per ampere per every ten feet of distance (20 feet conductor length) covered
5.) #12 drops .032 volts per ampere per every ten feet of distance (20 feet conductor length) covered
.....we can see what size is worthwhile. I mostly like to minimize wire size to safe limits to make things easier to work with.
Tom
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