Bus size

Discussion in 'HO Scale Model Trains' started by prodigy2k7, Mar 7, 2007.

  1. prodigy2k7

    prodigy2k7 Member

  2. rogerw

    rogerw Active Member

    will it grow or stay at that size?
  3. rogerw

    rogerw Active Member

    Im still in the early stages of my layout. but I will run a heavier gauge wire for mine . My layout will be bigger also. the cost betwean the wire size is very small so why not go with the larger size . just my thoughts Thanks Roger
  4. prodigy2k7

    prodigy2k7 Member

    stay this size
    Is 14 gauge solid copper too big? Thats the smallest wire I can find easily.
  5. rogerw

    rogerw Active Member

    my guess is no its not to big. Thats what I plan on running on mine. You will have less of a voltage drop with that size wire. However I am relitivly new so hope you get more feed back Roger
  6. rogerw

    rogerw Active Member

    OH and also the smaller number on the wire the bigger size of wire.
  7. spitfire

    spitfire Active Member

    I believe 16 gauge is the thinnest you should use for HO. Some people go all the way to 12 gauge. The thicker the better. Wire is like your arteries - the thinner the more pressure. In the case of electricity, this extra pressure turns into heat. Sometimes, a lot of heat...

  8. Russ Bellinis

    Russ Bellinis Active Member

    It is based on ohm's law. I think it is talking about 2.3 amps at 110 volts. When you lower the voltage, you can increase the amperage, so at 12-14 volts you can probably safely handle 10 amps. That said, the bigger the wire, the less voltage drop. I think the least expensive wire you can buy is #12 gauge romex. If there is some housing construction near by, you might be able to get some left over scraps, if you ask.
  9. prodigy2k7

    prodigy2k7 Member

    I already have 18 solid copper, thats why im asking.
  10. cidchase

    cidchase Active Member

    22AWG 16.1 milliohms per foot
    20AWG 10.2 milliohms per foot
    18AWG 6.39 milliohms per foot
    16AWG 4.01 milliohms per foot
    14AWG 2.53 milliohms per foot
    12AWG 1.59 milliohms per foot

    Meaning that if you have 50 feet of 18AWG (25' in each of two leads), at a 0.5 amp load
    you will lose +/-0.15 volts, so your loco may see 9.85 volts instead of the full 10 (or whatever,depends on the loco). It's not much of a loss. For a smaller
    layout, it's almost negligible. Any wiring will have some voltage drop,
    proportional to its resistance. A bigger factor in voltage loss would probably
    be how many parallel feeders you have running from bus to track. These
    feeders alleviate the effect of poor joiner connections, etc.
    Dat's de numbers!!
  11. Torpedo

    Torpedo Member

    Take another look at the table in that link. You will see that 18 AWG is rated at 16 amps for "chassis wiring," which is more akin to your intended purpose than "power transmission." Power transmission assumes the wires will be bundled and in conduit and carrying at least 120 volts, as I understand it. It is concerned with fire hazards, which is why it is so low compared to chassis wiring, which assumes a single wire in free air. The power transmission rating is also extremely conservative with a very large safety factor.

    As cidchase has pointed out, it is the resistance per foot that counts, and you can easily calculate the voltage drop if you know how many feet of wire are involved and what the maximum current draw should be.

    Personally, I think 18 AWG is a bit too small for anything but the smallest layouts. For a 4 x 8, it should be OK, but it wouldn't be my first choice.
  12. baldwinjl

    baldwinjl Member

    I have to correct this one. The voltage controls the current through the wire, but the wire does not know the voltage, only the current. 2.3 amps is 2.3 amps. The wire has a resistance, as pointed out later, and hence will drop a certain voltage through the wire dependent only on the current. This generates heat, which is the reason for the limitation of current in the wire for safety reasons.

    However, in the DCC bus application, the voltage drop through the wire becomes important to us before the safetly implications kick in, depending on the bus length. Without going through the process, the general answer is that #18 is probably a bit small for your bus, #16 would be ok, #14 would be even better.

    Since you have #18, you could double up the bus with that, and be fine, too.
  13. prodigy2k7

    prodigy2k7 Member

    I am going to do DCC, with between 1-3 trains.
    Do you think I should get 14 gauge?
    I didnt wire it up yet, one thing im worried about is how big the wire is, the size is almost as big as the rail.
  14. rogerw

    rogerw Active Member

    I vote yes. Its not going to hurt and if you do expand the layout you will be ahead of the game imho Roger
  15. Old_Bob

    Old_Bob Member

    A very practical outlook, from a contractor:
    14 ga Romex or equivalent is easy to come by as a two conductor pair, and it is relatively easy to terminate. There is an abundance of tools made to handle it. Anything larger becomes a pain to work with; it doesn't want to bend easily. 18 ga is the size of doorbell wire or sprinkler wire and it can be somewhat fragile to work with. It is easy to nick when trying to strip insulation; if your stripper is not correctly calibrated, you may not like it. 16 ga may not be commonly available at a home center.
  16. prodigy2k7

    prodigy2k7 Member

    I might just buy 14 gauge and use 18 for feeders, 20-22 is hard to find.
    Is 18 too large for feeders?
  17. rogerw

    rogerw Active Member

    From what ive read I think 20 gauge is a good feeder size but not 100% sure. allso I would use solid and not stranded wire for feeders.Thanks Roger

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