Telephone wire for switches

[Anonymous]

I read that regular telephone wire is good to hook up various switches and accessories. They have four color coded strands and you could actually keep them wrapped for running wire to your power supply. My question is that 1. Is the wire strong enough to hold the proper current? 2. Are there any other ideas on this subject? Thanks

[MisterBeasley]

That's what I use. I get a hundred foot roll of 4-conductor (2-pair) phone wire for under $10 at Home Depot. I looked online for 3-conductor, and found that the phone wire is cheaper.

My turnouts all use twin-coil switch machines, a mixture of Atlas and Peco. (As an aside, if I had it to do over again I would go Peco all the way, or maybe even upgrade to Tortoises.) I use a Capacitive Discharge circuit to give me the extra "kick" that the Peco's seem to need. All of this works flawlessly with the phone wire.

I'd like to hear from Tortoise users about what guage wire they use, and whether anyone has had problems because they used wires that were too small.

[ARTHILL]

I use 22 gauge for my tortoise. Seems to work fine.

[Anonymous]

You might also look at CAT 4 or 5 cable at Home Depot, Lowe's, etc.
It is 8 conductor which woks well with the Tortise machines because they have 8 positions. Two for power and six for switches. This can really cut down on the spaghetti wiring that can occur when using multiple pairs.

[tomikawaTT]

I've been using telephone wire (salvaged from various sources) for more years than I care to admit. The switch machines are those Japanese-made twin coil monsters sold in the US by Kemtron and others. No overheating, and reliable operation over distances up to 20 yards as the wire ran.

If telephone wire can handle those machines, anything less power-hungry will be no problem.

Chuck

[jeffrey-wimberly]

Telephone wire works very well. I use 6 wire commercial cable on my layout for everything. Sound, turnouts, lights, signal and rail power as well as other things. It works very well and I can get it from the telephone company. They're throwing away partial spools all the time, sometimes with up to 10 feet of wire still on them.

Jeffrey Wimberly, Leesville, La.

I'm out of my mind, but leave a message anyway.

[soapbox]

[Bob grech]

The subject of choosing the correct wire guage can be done using Ohm's Law. Skipping all the math, the smallest wire guage I recommend for a layout under 50 feet is #18 wire, but I prefer #16. Another consideration is how many machines are drawing AMPS? Too small a wire will increase resistance. This will have an adversely effect on performance (Tortoise switch machine will run slower than intended) thus creating an overload condition that can damage your motors or even burn them out.

[Kent]

I use both telephone wire and Cat-3 wire to run Atlas snap switches, works fine.

[Leon Silverman]

Ohm's law equations are what are referred to as "steady state", or continuous duty equations. Solenoid switch machiness, such as Atlas, Peco, Kemtron, etc. operate only momentariiy. Consequently, the relatively high current is not sustained long enough to significantly heat up the wire. Wire gage is not an issue in this case.
Tortoises, or motorized switch machines, draw a small but continuous current which will heat up the wire. If you can comfortably touch the wire after fifteen minutes of operation, your wire choice is okay. If it feels too hot to hold onto, double the wire and repeat the fifteen minute touch test to see if the wire capacity is adequate.
Overloaded circuits cause fires because the wires eventually reach a temperature hot enough to ignite a combustible material (e..g. wood ,paper, or cloth) that is in contact with the hot wire or the sustained heat dries out and disintigrates the insulation around the conductor, causing a much higher current to flow through the resulting short circuit.

[fwright]

The whole issue of wire gauge comes down to 4 factors:

1) Can the wire safely support the current it is carrying?

2) How much voltage loss is acceptable?

3) If there is a short, will the feed wires or the device wires burn first?

4) If there is a short, will the circuit breaker, fuse, or current limiting device actuate properly?

In most cases, MRs cover #1 fairly well. After all, 20 gauge wire can handle 5 amps safely, and 28 gauge 1 amp.

For voltage loss, we are a lot more critical than house wiring, especially if using DCC. A voltage loss of 1 volt in a 12 volt DC circuit is generally considered unacceptable. Thus, the normal recommendation is to move up one wire size (smaller number) for our circuits. However, for a momentary switch machine, voltage drop is not a factor unless the power supply is marginal to throw the machine to begin with.

What happens when the push button sticks (even though not a short circuit) is a real concern. For #3, as long as the wire size is a couple of sizes bigger than the wire in the switch machine coil, a stuck push button wil cause the coil to burn up first - which is actually more desirable than overheating anywhere along a wire cable run. This might be questionable using Cat-5 or similar cabling - I believe the individual wires are only 30 gauge or so. Modern telephone cable isn't much bigger, though the older stuff was generally around 24 gauge or so. A good CD power supply has the beneficial effect of limiting current after the capacitor has discharged, which prevents burning of the coils (or wire run).

The last one is a gotcha many fail to consider. How many of us use a toy train transformer or other 4-5 amp device as a power suppy (I do). The problem is that when too small a wire is used over a distance, the wire resistance adds up enough so that even if there is a short at the far end, the wire resistance stops the transformer circuit breaker from popping. The wire sits there cooking with 4 amps flowing through it (limited to 4 amps by the wire resistance), but the circuit breaker won't pop until the current reaches 4.5 amps. What I am saying, your wire must also be sized to handle the short circuit current or circuit breaker rating of your power supply (it's max power rating) unless you have some form of current limiting in effect. In the switch machine example, with an 18VA power pack and no CD unit, you need 26 gauge wire or bigger. If the power pack is bigger, you need even bigger wire, or install the CD unit.

Hope this makes sense
Fred W

[Anonymous]

Overloading a Tortise machine will not burn out the motor as they are designed to be in a stalled state at all times. They only draw about 25ma so small wire work just fine with them. So even if they are fed only 6 volts they will not burn out. They seem to work perfectly down to 8-9 vdc.

[johnny.5]

Cat 5 wire is 24 gauge also.
John

[tjerrard]

I use #12 for bus from Digitrax DCC DB150 unit, #22 short run feeder from bus to track.
For turnout motor (Peco motors with CDU attached) I use #14 bus and #18 from bus to motor and switch.

All works well.

Tom

[Walter Clot]

I even use the telephone wire for power to track. I've never had any problem!