Question on buss wire run

I have done exactly what you describe for low-voltage yard (outdoor) lighting, and it resulted in more uniform brightness from my lights.  You're correct in your thinking; connecting both ends of the run to the transformer resulted in less voltage drop at the point farthest from the transformer.  My only concern with doing it for layout wiring is (and I must defer to the TMCC and DCS experts on this point) whether it would result in something like a ground loop that could interfere with control signals.  I would think not because this is lighting wiring we're talking about, but stranger things have happened.

Whether doing what you propose would benefit you would depend on how large your buss wire is, and how much lighting load you have.  Returning to my outdoor lighting scenario, previously I used 14-gauge wire with 4-watt incandescent bulbs in my 18 lights and the 72-watt load at 12 volts DID cause significant voltage drop from one end of my backyard to the other.  But now I use LED lights and the load is so much less that the voltage drop is negligible, so I don't connect both ends of the run to the transformer.  You could always try it and see if there's a noticeable change in brightness in some of your lights.

Hope this helps.

It's fine for TMCC, but DCS may not like it.

Thanks for information. I'll give it a try.

Lionel suggests star wiring for track over a circle for using command i.e. a bus to a center point then legs reaching out. Not everyone uses this though. The circular version is to connect two bus ends to the transformer, then cut the legs apart at the far end.(run two buses. one going clockwise, one going counter clockwise. )

The reason is the shortest path is best; it has less resistance.  And for two short busses that are terminated, the current will take the shortest path at that moment, once the loco passes the far point it simply switches which wire its drawing from to the shorter.

"Every layout might be different" too; location, power supplies, wire lengths, etc.

The shortest path applies to accessories too. In the end, you save some wire using two buses too

A circular buss can potentially confuse a signal.  Because you can not guarantee the future use a star pattern.  Then you will always be open to using DCS down the road even if that is not on the agenda right now.  Depending on the run, I use 10ga, 12ga, or 14ga star runs.  Short 18ga drops.  Different color for each wire.

I'm using 12 ga as my bus line run in circle pattern for two runs. Short 18ga drops  colors are red and black. I want to create a star pattern - I have two independent lines  run my layout. I need a suggest to do. 

Thanks

Chuck, Simply cutting the circle at a far point would break the circle for command purpose as Tom mentions. How much closer to running an exact star you need may actaully vary, you should test it, but be prepared for surprises for a bit. Breaking that circle would be step #1 it seems. Lots of folks ran command without ripping out every wire to run star. Other did need it....and more.   See what you have first.

I have always done the split loop for "around the room" even as a kid.

 Star wiring diagram can easily be found with advanced search here, or the net; but one buss, and all drops done off the end of that buss is "star wiring". 

He is talking about wiring for lights with an auxiliary transformer, not running trains. The complete circle is definitely the way to go.

John H posted:

He is talking about wiring for lights with an auxiliary transformer, not running trains. The complete circle is definitely the way to go.

I noticed that; much of our elaboration was unneeded; strayed. But the "shortest path" rule still applies, so why loop vs two lines using X inches less wire. (other than looped, it acts like doubling up the wire for more amp capability. But that shouldn't be needed if you've built with good wiring size standards)

Paul Kallus posted:

I was wondering if its a good idea to hook up both ends of a buss wire to aux. transformer. Example: I am running a circle of buss wire around (underneath) a city portion - from buss wire vertical street light feeders will be connected at approximately 20" intervals. Start of buss wire is at transformer; question, do I connect end of buss pair back to transformer or do I end the "end" of the buss at the last street light? Does that make sense? I would think connecting both ends back to transformer would provide better voltage, but am really not versed on electrical current and voltage.

Until the coming of LED lighting if you passed a house with those "Malibu" lights you could tell who had a loop and who just ran a straight line of wire as the loop normally had all the lights about the same brightness, while on the straight line of cord each light got dimmer as they progressed towards the end.