After Phasing my Lionel ZW's

You can, but make sure that it's a pretty fat wire. It has to carry all the current for three tracks.

I thought so, it's a large layout and I didn't want to have a lot of resistance for a 100 foot run, so I used 14 gauge for power and common.    I cannot wait to post pics, probably a year from now :-)  It's a 600 square foot layout (20.5' x 29.5' ) with 3 levels. I will be able to run 7 trains and do two switching operations at the same time.  I will probably go nuts trying to wire this sucker :-)

Thanks for the response, Bob

For a 100' (total length) run of #14, you are looking at .26 ohms.  At the max current of 10 amps (for most modern transformers) you will have 2.6V of drop.  If half of that is a Common wire also feeding other circuits, the drop will be even higher.

The good news is that the track may also contribute as additional conductors if it isn't an isolated block.

I'd run separate conductors.

Bob,

    I agree 100% with Guns on this one, run separate conductors, especially with the original ZW's.

PCRR/Dave

I would run separate conductors as well

Only way to go is separate wires & that will also help you trouble shoot later down the road.  Personally I would use 12AWG instead of 14AWG

.The 14g is already there? And I assume stranded vs solid? Overkill in wire size is always better than being undersized.

As Dale noted, the outside rails if not isolated, add some beef to the capability there, leaving the center rail circuit "light".Running 12g to a rail common connection and junction for outside rails, then 14g common feeds, and 12g again for feeding the variable center drops  could help fatten things withoutf feeding the trashcan as much. Or just use the 14g for your accessories.

Adding a common line to match each variable would be the minimal approach.

Doubling wire would work too.

Why all the interest in running separate common vs a bus? Circuit protection? Signal protection? Mixing of variable common and variable "hot" transformers?  All I get out of it is more wires from transformer to track in conventional.

(PS,  Not all those ZW circuits are protected, you should add something.)

Other than circuit positioning drop issues off 203/220, I can't think of a reason I've run into as to not to bus the common NEARBY to a junction block wiith an appropriate gauge, then run feeds off the common junction block.

Thanks guys, I certainly appreciate the advice. I started with #12, and too hard to work with.

Just trying to save wire runs with the common wire. Each line has its own hot wire #14. 

Interesting note is that I tested the track without any additional drops. I used an LW with alligator clips to the track and my MTH Switcher ran the entire loop without losing speed, so at least I know I have good connectivity on the gargraves trackage.

Bob

The significance of the conductors' resistance depends upon the trains you are running.  If you have multi-motor diesels pulling passenger cars with incandescent lights, or steep grades, the voltage drop becomes more important; otherwise, whatever works!!

Ive got my layout wired in "star" wiring with the longest wire run being like 30 feet and the longest track block about 12 feet,I used 16ga 2 conductor speaker wire.  I get at least 17 volts on the layout and my trains dont care. I also took the time during the rewire thsi summer to label every wire splice and every terminal for troubleshooting. I took my shameful ratsnest wiring to a work of art in just 90 short hours of labor.

Take your time on wiring and do it right the first time, you will be glad you did when you have a problem and you will have a problem at some point.

This site and all of you have been very helpful. Waited my whole life to do a large layout and I want to do it right.

Thanks, Bob

With new equipment you'll likely be fine at 14g.

If you'll be double or triple heading PW dual motor engines; 12 gauge