Hookup wire

A lot of us like to run multiple engines and or lighted passenger cars and that draws more wattage from the transformer, so I think that some people have jumped the gun and gone with over-sized wire just to be safe.

Personally I find 20 gauge wire to be quite small and may heat up easy, unless used with an accessory that only gets occasional power.

Lee Fritz

It's not just the heating of the wire.  It's voltage drop over distance(wire has resistance).  If you can tolerate a 10% voltage drop, 2 volts out of 20 volts then you need 14 AWG to go 25'.  If you are only going 10 feet and can tolerate a 10% voltage drop then you only need 18 AWG.  My examples used 10 amps current.  More or less max current draw would equal more or less wire size.

You can Google many different tables and calculators. I used the one at:

http://phd.boschsecurity.com/wiregage_cal.cfm

It's the voltage drop x current = power loss that generates the heat.  Which at extreme will melt the wire like a fuse.

This is the short answer.

Dan

Gilly, Tables make assumptions.  The table you posted shows for 14 AGW wire - 32 amp for chassis wiring and 5.9 amps for power transmission.  Chassis wiring would be very short distances ie a foot.  The NEC says 14 AGW is good for 15 amps probably assuming a ~ 120' run, 7.5% voltage drop.

As for the original ZW set hook up wire, 6 feet, 10% voltge loss - 20 AGW would be ok.

dan

Maybe we should be using MONSTER WIRE, like all those addicted to sub-woofers and such.

Funnily enough, that is what I use for my track power connections. It works really well. 

N.Q. D. Y.

The stuff I'm talking about is 6 or 8 gauge.  Seems rather much for powering choo-choo's

The bigger the wire, the better the signal. 

Larger wire handles the higher command voltage better and minimizes the loss at the track. 

I use 14 ga buss and feeders and have zero voltage drop and my feeders are 10' apart.

I just ran into an example of why you don't want to use wire that's too thin. Switches generally have internal wiring connecting the center rails on all three tracks. I was running a train on our museum's Standard Gauge layout and discovered that the track on the exit side of one switch was dead. There was an open circuit between the center rail on the main and the center rail to the exit. I took it apart and discovered that the power wire had blown up. The engineering geniuses at MTH had used 26 gauge wire (!) to connect the center rails, the same gauge wire they used on the other internal wiring (which only carries signals, not main power). What probably happened is that there was a derailment and short, and the power wire inside the switch blew before the breaker could pop. This was only a few inches of wire, but it couldn't handle the load and blew out. I replaced the wire with heavier stuff and installed power drops on all three sides of the switch. 

Moral of the story: 

1. Don't count on an MTH Standard Gauge switch to carry power to the siding.

2. Skinny wire is a really, really bad idea. 

I use 14 gauge wire for the Standard Gauge layout at the museum, where the longest run is about 20-25 feet, and 16 at home where the runs are more like 10-15 feet. The 0 gauge guys have some very long runs and use 12 gauge. 

I've made the small wire mistake thinking I would never enlarge my layout. I was wrong. I now use 14 gauge wire and feel comfortable that will be sufficient no matter how much the layout grows. 

My DCS signal strength is all 9's and 10's. I can run as many trains as I want and never see a voltage drop or weak spot.  I bought 250 foot rolls of strained wire. If I would have done this in the beginning I would have saved both time and money. 

You only need MONSTER wire for a monster layout.  14 agw is good for a run of 36 feet, 10 amps and a 10% voltage drop.  If you are not pulling 10 amps you will not get the 10% voltage drop.  You design for worst case.  Use stranded to get a good Legacy or DCS signal.

Dan

I did use 14ga on all power runs and 16ga on track drops which are 8' apart and reach the 14ga in 6" or so.

Works well as you-all indicate.

I have one of those Lionel power connectors with a "Made in Mexico" label on the underside which came with wire I wouldn't trust to power a flashlight bulb with a C-cell battery ...

That is the stuff I'm talking about too.  I got a good deal on a large reel of it some years ago. It may be a bit larger than I technically need, but it works perfectly, and I never seem to suffer from any voltage drop or signal issues.

I firmly believe in over-engineering rather than under-engineering.

You should see the foundations for my roadbed on my garden railway. The trench for the track is over a foot deep, lined with root-stopping fabric, and then filled with 4 inches of small stones, 4 inches of large gravel, and then topped with up to 6 inches of medium gravel before the track is laid on top. 

N.Q.D.Y.

As an engineer - an electrical one at that - I firmly agree.  As I said earlier, I use a minimum of 10 gauge and buy 8 for longer.  I have one 35 foot length of #6 in there, too.  Big wire "nukes" any of the potential issues you may have with voltage drop, signal and (if done well) ground plane problems that can plague a layout with "appropriately sized" wiring.  I'm just not willing to take any risk at all.  It's like building my house: I had the foundation doubled in strength - seemed like a prudent pre-caution.