Is this wire a decent wire to use ?

What are you going to use it for?

Track power with DCS ...will get a roll of red and a roll of black.    Will get the 18 or 20 gauge stranded for accessories if its okay.

IMHO   The 12AWG is way more than you need. I wouldn't go with anything bigger than 16AWG. It's your layout, use what you want.

Lowes has the same wire in 14 gauge, which I recommend unless your layout is in the 8'x4' range.  16 won't handle several locos on a large layout.  If you have a large layout and use a common bus running around the layout, 12 would be a good choice.  The issue isn't wire heating, but voltage drop which has great effect on a train layout.

For DCS I would use the wire OGR sells from their web store (OGR's wire is very nice and really well suited for DCS wiring), following the guidelines in Barry's book as closely as I could. I wired my layout this way and it works very well. Have yet to have a problem with it. I used MTH terminal blocks, #14 OGR wire from TIU to the terminal block, then #16 from terminal block to power connections at the track blocks. I later added Legacy by connecting the Legacy 990's U terminal (one wire) to the black output terminals on my TIU. That also works very well.

IMO, THHN wire is not ideal for layout wiring, it is more for use in conduit, as in commercial buildings. It is not very flexible and I find it a pain to work with for layout type or panel work. If you want to use the single wire like that try to find MTW (machine tool wire), it is a lot more flexible.

You could still use smaller wire on a large layout if you feed terminal blocks fed by 12awg. Thhn is not very flexible under track. If you are using DCS, you can handle some voltage drop, because it will operate on lower than 20v. I have a 16'X20' layout and used 16awg as feeders to a spot under the track, and then a short 18awg through the table on all my blocks. 10s everywhere and I can run four trains easily.

It's very nice wire for power bus use, I'd use smaller drop from the track.  You really can't have wire too large, other than the difficulty of wiring it. 

As far as the OGR wire, for 250 feet of #14 (2-conductor), you'll pay $90.  Here you're getting 500 feet of #12 for just over half that!  Since this is single conductor, the price is half of what the OGR wire costs and you're getting #12 vs. #14.  I'd say it's a pretty good deal.  If you favor #14, you can have that for $34 a roll of 500 feet: http://www.lowes.com/pd_293638...Id=50149798&pl=1

Comparing apples to apples, you're getting #14 wire for 1/3 the price with the Lowes wire.

It also comes in various colors as well for convenience of wiring your layout.

Based on experience, I concur with the gunrunner.  Too thin a wire seems to also impair DCS signal.

How about a little electronic math.  18 ga wire would be 157' feet , measures 1 ohm of resistance; 16 ga wire would be 250 feet measures 1 ohm; 13 ga wire would be 500 feet measures 1 ohm.  Using 18vac at a max current draw of 5 amps gives you 3.6 ohms resistance.  Does anything draw that much current using 18 vac from transformer.  You do the math.

Thank you all for the thoughts.     I think I am going to go with the machine tool wire in 14 gauge  I don't understand the resistance and all of that but I was just talking to a friend of mine who is an electrician and he agreed with RTR12  that the mtw wire although more expensive is easier to work with for what we do with it.  He said he could pick it up for me also when I am ready.   Thank you again all ..this forum is awesome.

Teledoc, I know the math & the theory but when I'm drawing 8 amps or more per channel, I see voltage drop.  Running passenger cars with incandescent bulbs can exceed 5 amp easily.  Before I rewired cars to LEDs, if I had two passenger trains running 9on the same channel, the 10 amp breaker would pop.  But the original poster has made a wise decision.

TeleDoc posted:

How about a little electronic math.  18 ga wire would be 157' feet , measures 1 ohm of resistance; 16 ga wire would be 250 feet measures 1 ohm; 13 ga wire would be 500 feet measures 1 ohm.  Using 18vac at a max current draw of 5 amps gives you 3.6 ohms resistance.  Does anything draw that much current using 18 vac from transformer.  You do the math.

OK, let's do the math.  Assuming #14 wire, which seems to be the choice here. let's go with a total run of 100 feet.  Of course, since we have to go out and back, it's actually 200 feet.  200 feet of #14 wire has 0.505 ohms of resistance.  Doesn't seem like a lot...

If we use your figure of 5 amps, that's a voltage drop of 2.5 volts!  Suddenly, that resistance takes on a whole new meaning when you're dealing with low voltages like 18 volts maximum, we've just dropped about 14% of the voltage!  And yes, there are some configurations that draw considerably more than that.  Let's take my Vision Line Big Boy, it draws a measured 4+ amps running with no load with all the smoke features enabled.  Let's add in ten lighted passenger cars at around 400ma each, there's another 4 amps.  Now we're dropping 4 volts!

Heavier wire is better.

If you are comfortable with 9th grade math, the following table will greatly simplify these calculations.

Each copper wire size has a certain product of length and current flow that will produce a voltage drop of 1 volt.

10  - 1000 Ampere-Feet/Volt
12  - 600
14  - 400
16  - 250
18  - 150
20  - 100
22  - 60
24  - 40

So, for example, in the case of #14 any combination of length X amps that multiplies out to 400 causes a voltage drop of 1 volt. If the length x amps =800 the voltage drop is 2 volts.

Personally, I like any voltage drop to be less than 1 volt, so I make sure that for any circuit the length x amps comes out to less than the value given above for the wire size used.

Better to big than too small.  I have to redo my feeder wire for my accessories because I ran #16 instead of 14 or 12.  Having to much voltage drop.

Ken M

Great subject : A lot good suggestions here. I run 18 gauge wires all around my Layout better safe then sorry. 

Good luck, John