Dispute over wiring...

You can add some science to the whole thing.  Sometimes hard to find, the capacity, amperage draw, of each accessory piece. Add them, if it is to be one accessory circuit.  Lighting would tend to be a constant draw, smaller gauge wire tends to have line loss, reduction in voltage do to small resistance in the wire, itself.  You may also want to add for future buildings, accessories. 

 Mike CT

This might help you on your decision.

 

 

AWG wire sizes vs. usable output in amps. Distance is maximum length of wire in one side of the circuit (from Trains.com).

Distance	1A	3A	5A	10A
8 feet	22	20	18	16
12 feet	20	18	16	14
20 feet	18	16	14	12
30 feet	16	14	12	10

 

You can see that a good amount of influence on your decision is the length of your run and the electrical load of the train you'll normally be running.

 

Neil

Nice table and interesting discussion, I would vote for trying to add up the watts you would be using and then use the table.  For example, on your accessories, assume you run them at 14v and you have 140 watts, you would draw 10 amps which would mean a #14 wire if you ran 12 ft.   

 

PS- I love these numbers but I tend to agree with the suggestion that a 14 bus should be fine.  If you really want to be conservative go with a 12 and forget it!

You can never go wrong w/12awg on your buss wiring.

 

Ken M

It's interesting to note that a 25 ft wire is easy to do.  I worked multiple runs to a remote section of the layout one Saturday. Up a wall, across the ceiling, down another wall, and leave enough wire for the remote section wiring, was 40 ft.
Also note: Neil's chart mentions one side of the circuit, both wires would double the length.   Total of at least 10 wires or cables X 40 ft. (400 ft)   A fair amount of conductor.
Wiring started here.

To here, and up the wall. Note the 14 ga solid track circuits, are added here.

Across the ceiling and down the wall.  Coiled wire is for final hook-up.

The brown wire is 18 gauge solid thermostat wire, used for switches and accessories. Largest cable has 8 conductors.   Again black and white are track circuits.
Area to be wired.

The area slowly comes to life.

By the way, a lot of (copper) wire being sold now is actually copper clad aluminum. It is just fine for all the needs that solid copper wire supports, but has more resistance per foot. So if you are using copper clad aluminum, going up a number in the gauge is a good idea.

If you cannot tell which you have, solid or copper clad, cutting the wire smoothly and looking at the center of the conductors will show them as being silver colored instead of copper colored and the outside ring of the wire will show the copper color.

Another point of this discussion is the number of conductors in a cable assembly or conduit. There are NEC (National Electrical Code) charts that deal with this.  In general the more conductors in a cable or raceway, the larger the wire size for the same amperage capacity.  

Does it really need to be that complicated? Not much difference in price for the wire, so when in doubt, go bigger. That won't cause problems later, unlike going too small, and then wishing you went bigger to start with.

I vote with Laidoffsick.  I'm no mathematician, and would just go bigger if any doubt.

Exactly, it's only a cheese sandwich.

Based on my 70+ years of running O-gauge, I strongly suggest using 14-gauge feeders.  It is not overkill and goes a long way to enjoyable operation.  My 70+ blocks are each fed by 14-gauge, and I use common buss ground, which is a 12-gauge loop (goes completely around layout with both ends tied to transformer "U" ground posts.  It doesn't take much voltage drop to affect train operation. 

Lots of good input here. Thanks....

I go along with all the others, when in doubt, use bigger wire. I am using #14 to terminal blocks, then #16 to all track blocks. Layout is currently 6' x 16' and it works quite well here. I plan to expand in the next year or so and the same size will be used for additional terminal and track blocks.

 

Wasn't planned, but my wiring fits in with the chart posted above by GTW, however, I did have a pretty good idea I wouldn't be going far enough to require anything larger. Using larger wire now at the time of initial installation is pretty much painless, replacing it later after layout is built and you begin to have problems is NOT painless.

 

I am using the wire sold by OGR for all my track power, it's stranded and great wire. They have it in #14 & #16. I would recommend it to anyone. Like Mike CT, I am using #18 solid thermostat wire for switches, lights and accessories which are supplied by sources other than track power.

 

I would approch the question from a slightly different direction.  The wire size should not be smaller that what is appropriate for the circuit protection. Voltage drop is not everything. If you have 10 amp circuit breakers in your transformer, then the wire should be no smaller anywhere in the circuit that #16. If it is a ZW with a 15 amp circuit breaker the wire should be no smaller than #14. 

 

Voltage drop can can slow your trains down. Wire too small for the circuit protection can burn your house down. 

I use MTH Z-1000's. I'll check and see what amp circuit breakers they use. Thanks... My research tells me the Z-1000 breakers are set about 5-7 amps. So, how does this relate to wire size?

I use 18 gauge on my layout for everything without problems.  The G&O outdoor layout uses 12 gauge for long runs with short 18 gauge feeders to the track.

 

Joe

I queried all the O gauge operators at the Williamsport Train Expo (I think 5 guys) and talked to 4 long time O gauge train buffs at my LHS and nary a one agrees with 14 or even 16 gauge wire.

 

One fellow, Larry, runs O and the larger tin plate Lionel trains. He said he use 18 for everything. In fact, in had with him 500 feet or more of wire on a big wooden spool.

 

But, you have given me your best advice. So, I am taking it seriously....

Joe, do you connect to accessories with 18 gauge as well?

If you ever need to use a larger wire size than what you already have in place, just run another wire alongside of it and tie it into the same circuit. For example, if you have  an 18 in place, add another 18 and tie it into the first one. No need to replace and start over.

You're fine with the wire sizes in the table GTW gave above.  

 

However, I always use bigger copper wire than that.  As an electrical power engineer, I know I don't need to , but I also know why it helps.  Larger wire means less voltage drop and big wire is just a good way to avoid annoying little problems, particularly if you think you might run accessories or trains at or below half-position on your power supplies (i.e., under about 8 volts).   

 

 

I agree completely with Lee.  As an electrician for 43 years in construction on a service van I didn't get paid to back on my work so I always made sure it was right.

 

Ken M