How Long Can A Bus Wire Be?

Ohms Law - wire gauge and length will determine how much voltage drop occurs.  Use one of the voltage calculators on the web.  The first one on my search calculates an 18v 5A current will have a voltage drop to 13v at the end of 300ft using 12g bus wires.  Of course, you can always run a feed to the bus at both ends of the helix to reduce that drop.

I have a feeder from my electric meter to my water well that’s 2200 feet. 😆

Why not run the bus wire up the supports and make the bus runs MUCH shorter?  There's no reason to make it follow the entire helix, AAMOF that seems like a poor way to handle it.

Like John said, run a 12 gauge buss wire up the supports and run your 16 gauge feeder wires to track from the buss wire, you'll use a lot less wire that way. Electrical Wire isn't cheap anymore!

I've latch on to a Star Wire system? Visualize I'm topping helix with plywood to support second layout. Attachment shows the basic size. 7x11. The red block is a support pole. The two blue are planned drop down panels so I can reach all areas of the top. I'm incorporating a frame of 2x4's in the area of the post to attach an under cabinet appliance holder for the ZW-L. It will fit in-between the two layers. Its from that area I like the idea of star wiring to connect everything. I'll need a switch to choose between the two layers. A true "star" pattern of wires attached to the bottom of plywood running to the supports.

I see no need to add blocks for train separation.

I like the idea of spade and crimping connectors.

I read conflicting answer to how many feeders to add. The top is not a concern at this time. Its a simple double track oval.

All my locomotive power is K-Line ABA with TMCC. Most of the track is either 72 curves, 14 inches, 8 for each arc and two 30 inch straight track connecting the 2 arcs. Less than 2 percent grade. One read using a inclination tool  showed 1.45. Will see.

I've read ever track section. I've read only each level.

Are there any issues using the same gauge wire for both Bus and Feeders?

I need to make a drawing.

@SilverChief posted:

I see no need to add blocks for train separation. I do not run blocks at home (10x14 layout) nor at the club (75x8) over 150 feet of track per loop.

I like the idea of spade and crimping connectors. Do what you want, I solder so I know it's good, crimp connectors take time and money for every connection (true of all connection types) so pick your poison.

I read conflicting answer to how many feeders to add. Break it down to this simple concept- how many track pieces have to depend on the pins for electrical connection before a feeder? That, and coupled with the rail type determine how much resistance any piece of track might have between it and the nearest power feed and ultimately the power source. What is the propensity for a track to wiggle free, have loose track joiners and ultimately have power drop or power loss over time and usage? How hard is it to then later, go back and fix this problem track later? Bottom line- better feeder system now during building- prevents trouble shooting and ripping out track and adding feeders later. Pay now or pay later, your choice.

Are there any issues using the same gauge wire for both Bus and Feeders? Cost, stiffness of the wire, trouble making connections. Again, feeders are fat enough to handle the local current with low voltage drop over a short length. They often have to go through holes, be connected to the track, and then bonded to the bus wiring. Bus wiring needs to be heavier for distance and voltage loss reasons.

I used 16 gauge feeders, 12 gauge bus on my home layout. Club really is pushing the limits, mostly 16 gauge feeders, but the bus wiring isn't 12, maybe 14 gauge and yes, we have drop at the far ends of the table loop (transformer feed is near the middle). Ideally we need to pony up and buy 80+ feet of heavier copper, at least for the bus.

My test? I run a conventional Lionel 726 in good shape pulling a whistle tender. Using the Z4000 tranformer, I set 11 volts on the track and note the speed of the engine running around the loop. On the 75 foot club table, you can tell when it's in the middle near the transformer input vs the far ends of the table. Another test is lowering the voltage to where the 726 just creeps along when near the transformer feed. If it can make it the entire loop and not slow down and stop stalled, then we have a successful power feed system.

I used #18 wire for track drops and #14 wire for my bus from the power panel.  Running with an actual measured 8 amps of power draw on the mainline, I never see a 1 volt drop anywhere along my mainline or my secondary loops.  My longest run from the panel to a power drop is around 20 feet of #14.

A wire drop calculation shows about 0.9 volts at 8 amps for a 20 foot run (40 feet of wire. using #14, looks pretty close to what I experience.  Note that for a 20 foot run, you would really have 40 foot of wire as you have to figure in the return path.

While using heavier wire won't hurt anything, for the most part it's needless expense for little to no gain unless you have long bus runs.  My layout is 12 x 24, and my power source is centered to minimize the length of any wire runs.

Ditto here on John's specs with roughly the same lengths (21').  I run a mere 14awg bus to 18awg feeders... both, solid copper 'strand' (not copper over aluminum) ...and, a ton of feeders (about, every 6'-7').  All of my Legacy locomotives can traverse all power districts and crossovers at Legacy speed step 1... no stalls.

I also run the ZW-L for my power districts and a ZW for the tortoise machines & accessories.

My RR cave's two longest dimensions are 60' X 45' irregular.   Roughly 200 linear feet of walls not counting the various peninsulas.  Approximately 150 switched blocks are fed directly from a dozen 12 or 24  post MTH terminal strips.

There are no spliced buss wires.  All runs are unbroken star connections.

To be on the safe side I ran 10 ga to the longest points, 12 ga for the medium runs and 14 ga for the shorter runs.  The long 10 ga probably was not necessary but I had stock so  it got used.

If I had an 8' x 8' layout 16 ga would be fine.

Since discovering on board battery R/C every thing I just wrote is kind of unnecessary.  However at this point I will keep the wires for my fleet of DCS 2 and 3 power units.

I do have to say I find the newer Lionel sounds to be impressive.  Maybe better speaker enclosures would improve my Proto Sounds,  speaker enclosure recommendations?

Key point- at club I have to cater to 2 different users, "conventional only" typically running voltage sensitive postwar and or Williams drawing high amperage- and so even 1/2V drop matters- and 1 volt it matters a lot, and command operators, where 1V typically is not the end of the world.

And, this proposed track has grades in the form of a helix, where speed is going to be critical, up VS down is going to matter a great deal if conventional is ever attempted.

And lotta amperage!!!

"If doable was going to run 4 consists with ABA TMCC at the same time."

You can single handle (program or setting specific to the ZW-L) all 4 outputs controlled with one handle and thus match voltage output. Hence, why I said you would not necessarily need to make dedicated power districts, however, you might wire a given area and feeds to a given ZW-L output.

Again, because you said this "If doable was going to run 4 consists with ABA TMCC at the same time."

If one train draws 4-6A typically, then 4 times that is technically over what one channel should be loaded to (10A max). Hence, technically, we are hoping 1 train per general area and thus powered by one of the 4 ZW-L outputs. Since there are 2 separate loops, that would be 2 outputs technically parallel per loop, but because of distance one is say covering one half of the feeds and bus, and the other the other half.

The shear resistance involved: Outer loop has sixteen 14 inch curves 16x14" plus 120" of straight =344". Inner loop runs slightly shorter. Rounding up for extra  that's 344"x10=3440 or 286+ feet.

Again, we are hoping for load sharing, general equalization, and 4 trains across 2 large loops as I understand the intent.

You could power district it up and divide using insulated pins, but I think the one handle and load sharing- works better at least by my experience and knowledge. The shear distance, and amount of wire, plus actually beneficially ensuring there would not be a differential as an engine passes from one district to the next would be better, than having the train and potentially internal wire from one pickup to another bridging a power district.

Now I'm thinking an Octopus arrangement with two parallel Bus lines in the oval shape of the two layouts. A switch arrangement between the two. Easy feeder lines from the top as needed. I have 12 supports(2x4's) that are spaced symmetrically around the track that support the Helix.

My thought was to tap into the bottom bus line and run down each support with Bus gauge wire. From there I could just add the short feeder at each level.

Twelve potential touch points around the 5 different levels for feeders off one wire per support.

Does this seem right in my thinking? Can I have multiple Bus lines off of one?

Correction - I have more than 12 supports. The 12 supports are for the curves. Straightaways have additional 2x4's.

If you're running TMCC or Legacy, you'll have to run a ground plane wire on the underside of the helix.

Regarding the number of feeds, limiting the number of track joints current has to flow through is the metric to apply.  For a tinplate helix with 16 track sections per circle, a feed every 4 sections (quarter circle) would be best.  A power feed every 8 sections (half circle) may be sufficient.

+1 on using a single power district per loop.

@Tracker John posted:

If you're running TMCC or Legacy, you'll have to run a ground plane wire on the underside of the helix.

That's the black wire, right? Red for power on the center rail and black ground on the outer track. TMCC signal through that ground, right? Thinking to myself here....

@SilverChief posted:

That's the black wire, right? Red for power on the center rail and black ground on the outer track. TMCC signal through that ground, right? Thinking to myself here....

No. That is not correct.

The  ground "plane" wire is connected to the earth ground of the house wiring - the third wire that goes to the third prong on the house AC power plug.

It's like an upside down antenna system. The TMCC/Legacy broadcast antenna is the ground wire in the house 110VAC house wiring.

NOT the black wire!  That's only half the TMCC signal.

TMCC radio signal follows two paths:

1.  The outside rails (common, or "track ground") that gets fed directly to the TMCC receiver from the loco's wheels, and

2.  Your house 120vac house ground wiring (the green wire) with a signal radiated over the air.  The signal gets to the house wiring via the round ground prong on the TMCC or Legacy base power bricks plugged into a 3-hole outlet.  The antenna inside your diesel's shell or handrails of a steamer pick up this weaker signal.

When you have tracks on multiple levels, the RF (radio frequency) signal radiated from the track common rails on an upper level can swamp the weaker signal from house wiring in the walls and ceiling.  Your TMCC/Legacy locos show the lack of good signal with a flashing headlight.

The solution is to provide a good source of the house ground signal that is generally called the TMCC ground plane.  There are extensive posts on this forum (search "TMCC ground plane") covering a variety of solutions to dealing with the issue.  In short, a wire (can be any gauge) connected to the house ground (the screw holding the outlet cover is a connection point) and run along the underside of the overhead tracks.

I've used metalized tape, wires, and metal bridges to carry the ground plane signal.  The key during installation is constant checking for a short between the ground plane wiring, track, and any other layout wiring.  Your multimeter is an essential tool.  Since you are building new, you can install the ground plane wire as you build the helix.  Run it on the center of the underside of helix sections.  You may need to run ground plane wiring on the underside of your upper level(s).

@Vernon Barry posted:

The shear resistance involved: Outer loop has sixteen 14 inch curves 16x14" plus 120" of straight =344". Inner loop runs slightly shorter. Rounding up for extra  that's 344"x10=3440 or 286+ feet.

My suggestion of running the main bus up the supports and then just tapping the drops off that cuts that 286 feet to a small fraction of that.  It's not necessary and actually quite foolish to run a 286 foot wire bus for this project.