There's ther power issues like Lion mentioned. Power is volts times amps, so if the voltage is much higher, you need less current for the same amount of power. As you step down voltage, you increase current, less losses in the converting device (usually a power supply) - that's why LED strips that take 30 amps at 12V don't need a special circuit to run them. It may be 30 amps at 12V, but at 120V it's more like 4-5 amps (no power supply is 100% efficient or it would be only 3 amps at 120V), easily handled by a common 15 amp household circuit.
The other issue is voltage drop. Run a 15 amp load on #14 wire for 40 feet across your house and while it may start at 120V at the box, at the outlet under load it may only be 112V. However, you typically won't notice that in an appliance, most US devices work on anything from 100-130V. So you have an 8 volt loss, big deal. But if your starting voltage was only 15V and you had an 8V loss, you'd most definitely notice how slow your locos ran with only 7V to run them. Reduce the current and.or use bigger wires to reduce the voltage drop. The drop is proportional to the wire resistence and the current draw, not the voltage carried in it.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
SouthPennThats an interesting ampacity chart. Seems the current ratings are a little low. I found current charts that had #14 wire at much higher values. Am I missing something?
YUP... You are confusing HO scale volts with 1:1 scale volts. His table was for 10 volts. Your table might be for 100 volt circuits.
At campus of LION, power pole outside has three 100A fuses. Naturally, you know that we handle thousands of amps in our facility. But on the pole that is 100 A at 7000 volts, where is inside we are on 120 v circuits.
Less Volts More Amps same power.
ROAR
The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
SouthPenn When my knees were still capable, I mounted the shorting bars close to the edge of the layout. I sit on a mechanics seat and roll right up to them. If I need to add some track feeders, I drill a hole next to the track, and feed some extra long wires ( or leave the spool on top of the track until you have enough ) through the holes. If I can't reach the feeders with my hands, I have a stick with a hook on the end that I can reach in and get the wires. I pull the wires to the nearest eyelet ( that are also near the edge of the layout ) and then to the nearest shorting bars. So far, this has worked for about 98% of my wiring.
When my knees were still capable, I mounted the shorting bars close to the edge of the layout. I sit on a mechanics seat and roll right up to them. If I need to add some track feeders, I drill a hole next to the track, and feed some extra long wires ( or leave the spool on top of the track until you have enough ) through the holes. If I can't reach the feeders with my hands, I have a stick with a hook on the end that I can reach in and get the wires. I pull the wires to the nearest eyelet ( that are also near the edge of the layout ) and then to the nearest shorting bars. So far, this has worked for about 98% of my wiring.
RR_Mel I agree with you on the LED/Switch Shorting Bars, great outfit . . . . But how does that help not crawling under your layout? I fixing to turn 79 and I need all the help I can get about not crawling. I have to get my grandson to do my under the layout crawling. Mel Modeling the early to mid 1950s SP in HO scale since 1951 My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
As usual, "it depends".
1. what kind of trains are you running?
ie: long passenger trains with older incandescent lighting can pull a few amps.
2. how many trains and powered locomotives running at one time?
3. how big is the layout? How long are you're longest wire runs for bus lines?
IMHO (personal preference) I don't like to skimp. Having larger gauge throughput throughout the entire layout wiring is the best and most inexpensive way to achieve outstanding voltage regulation, even with the price of copper being what it is. Keep in mind that any voltage drop will result in pulling more current (amps) to make up for the power requirement difference. More current = more heat. More heat = more resistance. More resistance = more voltage drop. It can become a vicious circle. It's one of the best ways I can think of to reduce component life expectancy.
Some of the bus lines on my layout are 40' long. Like I said, I don't like to skimp so when I rebuilt the layout I used 10 awg stranded for the bus lines and a minimum of five 18 awg pair feeders for each block (five 18 awg is equivalent to 10 awg). Every track section has a pair of feeders. All bus and feeders are twisted together. There is no voltage drop anywhere.
Mel:
Your control panel wiring is very well organized! I hope I can do half as well. I'm still trying to figure out how to keep decoder installations tidy.
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
SouthPenn I guess what adds to the confusion, is the fact that #14 wire is rated at 15 AMPs for house and general purpose wiring. I used 2 #16THHN wires in parallel; 2 wires out, 2 wires back. The wires are in the same hole or bracket as it goes around the layout. To minimize the lengths the power supply and Power Pro system box are in the middle of the layout. That way instead of a 60' feeder run, I have 2-30' runs. ( those are rough guesses, I actually think they are shorter. ) I have no solder connections as the track is feed from shorting bars. ( scroll down ) The shorting bars are accessible without crawling under the layout. I'm not getting any younger.
I guess what adds to the confusion, is the fact that #14 wire is rated at 15 AMPs for house and general purpose wiring.
I used 2 #16THHN wires in parallel; 2 wires out, 2 wires back. The wires are in the same hole or bracket as it goes around the layout. To minimize the lengths the power supply and Power Pro system box are in the middle of the layout. That way instead of a 60' feeder run, I have 2-30' runs. ( those are rough guesses, I actually think they are shorter. ) I have no solder connections as the track is feed from shorting bars. ( scroll down ) The shorting bars are accessible without crawling under the layout. I'm not getting any younger.
I use #20 solid for feeders, since it comes in a convenient roll of one red and one white wire, which matches the red and white I use for the bus wires - it's solid a alarm wire. But phone wire is fine, too. You will have lots of feeders all in parallel, so the current capacity should not be an issue, and if kept short there will be very little (if any measurable) voltage drop. Phone wire would NOT work well for home runs across a 6x10 layout. But for short feeders - no problem.
I use solid for feeders ebcause it is easier to poke through holes drilled through the subroadbed, but for the heavy gauge bus wires, I use stranded because it is much easier to snake along under the benchwork.
The text linked chart shows a much higher amp capacity for the wires because that's not a chart of capacity - that's a chart of how many amps have to flow through that size wire to melt the insualtion material. ANd yes, the lower number is also related to voltage drop, but without a distance you can;t just arbitrarily say it can handle say 5 amps. It needs to be specified something like: for #14 wire, there will be no more than a .15 volt drop over 20 feet if less if no more than 5 amps is carried.
1 volt difference is probably noticeable. a .5 volt drop generally isn't - shoot for no more than a .5 volt drop. And remember that just because the booster is 5 amps, doesn;t mean 5 amps will be flowing in a given segment of wire - that's a lot of HO locos sitting on one section of track. Where it does matter is being able to trip the circuit breaker. Too long a run of too small a wire can result in enough drop so that an effective dead short, like a quarter laid across the rails (which is not a zero ohm short - you do NOT press the quarter down for this), does not draw more than 5 amps, so the breaker never trips. If the breaker is set for 5 amps, you can pass 4.9 amps all day long - and 4.9 amps at 15 volts is 73.5 watts - a LOT of heat. Plenty to melt plastic sideframes and such.
carl425 Full disclosure: My 32' bus is 12ga and my feeders are 18ga.
Full disclosure: My 32' bus is 12ga and my feeders are 18ga.
RR_MelThe norm is about 3%.
This is my understanding as well from electrical oriented sources. I've never seen the <1 volt standard mentioned anywhere other than in MR related material.
RR_MelI will stick to the way I was taught because that has always worked for me.
By all means. Some of us are staisfied with "usually" some require "always" - ya pays yer money and ya makes yer choices"
I have the right to remain silent. By posting here I have given up that right and accept that anything I say can and will be used as evidence to critique me.
It's the .15 volt loss that makes the numbers so low. That's a very aggressive requirement. I've always heard that for DCC, the drop should be kept to less than 1 volt.
It's kind of off the mark for the OP anyway because that chart is also for 10 feet where the question was about 4 inches.
The way to calculate your own answer is to determine your maximum current draw for a stalled locomotive. If you can't test it yourself for some reason, 2 amps is a safe assumption since almost all loco's draw less than 2 amps.
Then google "voltage drop calculator". They will let you enter the wire size, length, voltage and current and it will tell you what the voltage drop is.
here's one: http://www.calculator.net/voltage-drop-calculator.html
Run the calculator for all segments of wire (and track) between the power source and the loco. Be sure to double all the lengths to account for out and back.
Then add up all the results and make sure the total is less than 1 volt.
Atlas code 83 rail has been measured to have the same resistance as 28 awg wire so you can use that in your calculation. This has been debated a few times here and not everyone agrees with that number, but I'd rather be conservative so that's what I use. I got it here:
http://www.dccwiki.com/Voltage_Drop
RR_Mel Just remember to not exceed the current limitations. Wire Size (AWG) Diameter (MILs) Ohms Per 1000ft Current Capacity 25°C (Amps) 14 64.1 2.524 5.87 18 40.3 6.386 2.32 20 32 10.128 1.463 22 25.3 16.2 0.914 24 20.1 25.67 0.577 28 12.6 65.31 0.227 32 8 162 0.091 40 3.1 1079 0.014 This chart is for low voltage i.e. 12 volts, 10 feet of #24 AWG has .15 volts loss at .577 amps. I have used Telco frame wire on my layout for over 30 years with out any problems, all you need to do is stay within the current limitations of the wire. Mel Modeling the early to mid 1950s SP in HO scale since 1951 My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
Thats an interesting ampacity chart. Seems the current ratings are a little low. I found current charts that had #14 wire at much higher values. Am I missing something?
LIONS use tons of phone like cables. Some even came from telephones. Mush of wire of LION came from an old 1920s pipe organ that was removed from the church. The buyer of the organ just cut the cables and left them behind. LION took the cables each with 67 conductors: 5 bundles of 11 wires and one bundle of 12. All conductors were white, none had plastic or rubber insulation. All insulation was waxed string. But the LION got it all installed correctly nonetheless. Needing still more afte all of that was used up, him bought many hundred feet of 25 pair cat 3 telephone cable. All kinds of color in that stuff.
LION uses the telco type wires for signals, relays, switch motors and stuff like that there. LION has FOUR 14 ga conductors enciecling the layout with access points every six to tenn feet: GREEN=GROUND; BLACK=600VDC (Third Rail ((Scale 8 volts or so)) ); RED=HOTEL POWER (Station lighting and etc); and WHITE=SIGNALS (signal and detection systems.)
Keep it simple STOOPIT!
Photo only shows the cables between this location and the TOWER, local devices were not yet wired to these binding points when this photo was taken.
The four wire cables were red, green, black, yellow, #22.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
I use phone wire for turnout control, both Tortoises and twin-coils, and for my control bus behind the fascia for my plug-in throttles. It works great for these. It's also fine for signal LEDs.
It takes an iron man to play with a toy iron horse.
Our club layout was wired for DC block control back in the early 1980's, they used telephone wire, #24. The club president was a phone worker.
When we wired for DCC using a five amp NCE system, we cut the feeders back to about six to eight inches long depending on the location. We ran #16 speaker wire for the buss. We run as many as ten sound loco's at times.
Do you know what size it is? Old phone wire used to be thicker than new wire. Telephone Cable: 22 – 28 AWG. Really old wire might even be 18.
I would never recommend doubling a wire because it was to thin. If you stick a 9 volt battery onto steal wool you can see how easily wire burns if overloaded.
j.....