What kind of transformer? How many wires in your bus? How are they connected to the track? How and where are you measuring voltage and power?
Bob Nelson
Why 8 wires in a bus? You should only need two. What is a "skrew" connector--a wire nut? What specifically is connected to what?
Chad, I'm still having some trouble understanding your arrangement. I think you're saying that your bus runs from the transformer, around the table along a rectangular path, then back to the transformer. Is there one wire or two in the bus? There should be two.
Then I think you have 8 taps on the bus, feeding various points on the track. Each tap should have two wires, one to the outside rails (the "common", not really a ground), the other to the center rail (not "positive", unless you were running DC). The taps can be smaller-gauge wire, but only if they are very short. The very last few inches can be smaller in any case, to make the connection to the track easier.
I think you may be using barrier strips ("Jones strips") for the connections, which are fine for this.
Do I understand your wiring correctly?
You need to have two wires in your bus, one for taps to feed the outside rails and one for taps to feed the center rail.
The reason I mentioned DC is because you have been calling the center rail positive. It is not positive when you run your trains on AC, as you are doing.
Another good (and faster) way to make your connections is to use wire nuts.
chad tm5000/trainstationim using 12 gauge wire and 14 gauge connector wire with quick connects for the fastrac track from lionel.
i'm sure this has been brought up before, but 12/14 gauge wiring is a complete waste of copper. the largest layout i ever helped wire was in a 40 x 45 foot space, modular with about 140 linear feet of looped mainline. a 14 gauge bus wire was run from the transformer stacks and distributed to about 4-5 spots in the modules and from that point, the suggested 16 ga wire was used independently in each module to the track.
once we fixed up a few builder quirks in individual modules, this layout ran for close to 10 year without one complaint about track power, often running multiple powered diesels, very long lighted trains, etc.
12 gauge wire is composed of very large, rigid strands which do not make very good electrical connections in small connectors, is very hard to work with and takes a lot of wattage to solder when that is called for . 14 (vs 16) gauge wire is equally difficult to attach/clip/solder to track.
It has been brought up before. Twelve and 14 AWG wire is not a complete waste of copper when you need a lower voltage drop than smaller wire can provide or, especially, when your overcurrent protection is greater than 10 amperes, as with a ZW transformer, for example. If it were a complete waste, you wouldn't have used a 14 AWG bus for your modular layout. Short taps of wire with less ampacity than your overcurrent protection are safe for the few inches that you might need to get from a bus to a track lockon.
The fact that something potentially dangerous, like electrical power wiring, has not caused any harm for a while is not a very good reason for tolerating an unsafe situation. You could wire a 120-watt ceiling light with 1-ampere wire, take all but two of the lugnuts off each wheel of your car, and cancel all your insurance policies, and never have a problem in ten years; but that would not be smart.
We run our trains at about one-tenth the voltage that our household liights and appliances use. But the currents in our tow-train circuits are about the same. Voltage is dangerous to the touch; so having exposed wires and rails is not a problem for us. But current is dangerous for catching wiring on fire; and it works just the same at low voltages as at high. So we should respect the same precautions that are used for our household wiring, including coordinating our wiring ampacity and our overcurrent protection.
I would not recommend using 12 AWG wire in small connectors either. Use connectors designed for that kind of wire. Wire nuts are extraordinarily practical for this, whether wiring layouts or houses. They easily make transitions among small and large wires; and they are easy to disconnect and reconnect for maintenance. Nevertheless, it is not hard to find soldering irons and guns that can easily handle 14 and 16 AWG wire and track rails too. For connections to Fahnestock clips and Faston terminals, use short taps as I described above.
i thought you might pick up that i meant 14ga is sufficient for any bus wiring while 16 ga is the easier to work with and certainly never the bottleneck in supplying the physical track connection.
reducing the number of junctions will far outweigh any benefit from a wire already rated to carry well over twice the current anyone would consider using. if you are reading household wiring limitations, hopefully note that most of those consider enclosed conduit, not free air spacing.
on that layout we put 8A breakers on the mainlines. please don't tell me you need 12ga wire to support those currents for less than 100' runs. you don't.
by the way, aside from hair dryers and space heaters, most household appliances at 117Vac use a lot less current (in the 1-3A range) than layout wiring.
What worried me was the unqualified statement that 14 and 12 AWG was always excessive. I often see confusion in postings between the two rather different considerations in choosing wire size--resistance and ampacity. In your case, it turns out that your 8-ampere overcurrent protection was in fact more than adequate to protect your 16 AWG wire, whose ampacity is about 10. Good for you. But too many folks, I think, are wiring 15-ampere Zs and ZWs to their track with wire that can't safely carry half that. Whether the trains actually draw that much--they probably don't--is not what is important. What is important is that the circuit breaker should trip when the current exceeds what the wire can carry. That isn't the case when a ZW is wired up with 18 AWG.
The NEC ampacities are stated for small numbers of wires, whether in cables or conduit. ("Not more than three conductors in raceway or cable or earth") Discounts of ampacity are imposed for larger groupings of conductors. Most houses in the US are wired with Romex-type non-metallic cable--no conduit. The ampacity numbers that I recommend are those imposed on that kind of wiring, which is quite similar to typical layout wiring.
The household appliances and lights that draw only a few amperes are the ones that are allowed to be plugged into circuits serving multiple outlets. In fact, there is no limit on how many outlets can be put on a single circuit. So the loads can easily be comparable to those on a layout.
what worries me is that anyone thinks they can get 15 amps out of a single ZW connection. not only would that be impossible given the internal wiring of a ZW, but where on Earth are you going to come up with any load that will consume that much power legitimately? we considered rating the mainlines at 10A but from a quick calculation we decided that even the most heavy demanding train was not going to use that much power.
you also still seem to be quoting home wiring standards. i have never seen a home train layout that uses conduit to distribute power. chassis wiring ratings (open air) for 14 gauge wire is over 30 amps and over 20 amps for 16 gauge. the other factor to consider with 16 gauge wire to the track is that multiple paths will be feeding a train sitting anywhere on the layout. with track feeds every other track section as our standard dictated, regardless of the least resistant path, you'd never get even close to the entire 8A distribution feeding through a single wire.
Can you explain what about the "internal wiring of a ZW" do you think prevents you from drawing 15 amperes from one output? Anyone whose circuit breaker has tripped after a derailment has drawn more than 15 amperes, or the breaker would not have tripped.
Your use of the word "legitimately" is important. Of course a typical train will not draw nearly 15 amperes. But several trains together can. And a fault like a short circuit can draw virtually any current, depending on its conductance, which is not at all guaranteed to be perfect. The purpose of the overcurrent protection--the fuse or circuit breaker--is not to deal with legitimate loads, but with illigitimate ones, whether on the layout or in your house.
You keep bringing up conduit. Houses and train layouts are hardly ever wired with conduit. What does conduit, or its absence, have to do with anything?
The ampacity that a wire is rated for depends on how hot you are willing to let it get, which often has a lot to do with what kind of insulation it has. The temperature and insulation circumstances that lead the code writers to limit 14 AWG to 15 amperes are very similar to those in a train layout, and that is why I think those limits are appropriate and desirable for the safety of train layouts.
Diversity can be important in engineering in determining how strong an individual rafter needs to be and what gauge is safe for a wire. The layout you mentioned may have enough multiple paths to allow the wire to be smaller. But that does not mean that everyone can use smaller wire without qualification. Nevertheless, there is some risk in allowing ampacity exemptions for multiple paths, in that a path can come open without giving any indication until some other fault occurs, whereupon the wiring overheats. The British are all right with this situation and allow what they call "ring mains" using smaller than normal wire. It is strictly forbidden by the NEC, except in very special circumstances.
Chad,
You fixed the problem by putting in the switch track. Good for you. Even though you fixed it, I want to express some thoughts on your first question.
Regarding your question, "...how can i get it steady...?" You must be referring to the meter readings on your MTH Z-4000 transformer. (Am I guessing correctly?) The readings you give, 12-13 volts and 1.4-1.0 watts (amps?) sound normal to me.
The Z-4000 meters only have two digits, so if the voltage is set to 12.5 volts, the voltmeter may fluctuate between reading 12 and 13. Most digital meters fluctuate when the input is half way between possible readings.
I have noted train current fluctuates depending on conditions where the train is running. On my layout (a flat sheet of plywood) engines draw more current going one direction than the other. I have it leveled to within one inch using scrap wood under the legs. (One inch over ninety six inches is about 1%.) Trains draw more current while negotiating curves.
Bob,
I have been reading this thread with interest. In the NEC there is Article 640, Audio Equipment. It describes requirements for cords and cables used between equipment and between equipment and loudspeakers. Maybe NAFPA should add Article 642, Model Railroads, to the NEC for establishing requirements for wiring model railroads.
..........Wayne..........
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