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Cat 5 Wire Max Voltage

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Cat 5 Wire Max Voltage
Posted by scott018 on Wednesday, October 31, 2012 7:49 PM

So what is the max voltage a piece of Cat 5 wire can handle safely?

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Posted by ATLANTIC CENTRAL on Wednesday, October 31, 2012 8:38 PM

50 volts - way above any voltages we use in model trains. I use it all over my layout for 24 volt relay control wiring.

Sheldon

    

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Posted by modelmaker51 on Thursday, November 1, 2012 3:18 AM

That's only half the story! Amperage also matters. It shouldn't be used for a DCC Buss as in the case of a short you could draw anywhere from 2.5 Amps to 5 or 10 depending on what your power supply is rated at, these amperages (current) could melt the cat 5.

Jay 

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Posted by ATLANTIC CENTRAL on Thursday, November 1, 2012 6:00 AM

modelmaker51

That's only half the story! Amperage also matters. It shouldn't be used for a DCC Buss as in the case of a short you could draw anywhere from 2.5 Amps to 5 or 10 depending on what your power supply is rated at, these amperages (current) could melt the cat 5.

Jay, respectfully, why would you assume he is planning to use it as a DCC buss? I would not even use it as a DC feeder drop, but the OP did not ask that question. He gave us no indication of what he wants to do - otherwise I would have offered more info as well.

I considered some long dissertation about ampacity as well - and then thought better of it.

Not every electrical question is about DCC.

Sheldon

 

    

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Posted by richhotrain on Thursday, November 1, 2012 6:07 AM

This is a big problem on the forums.  Insufficient information supplied by the OP leads to great difficulty in answering the question without providing a dissertation.

The same is true not only for electrical questions, but scale-related questions, track diagrams, whatever.  Insufficient information leads to incomplete answers.

Anyhow, back to the OP's question, what is the max voltage that Cat 5 wire can handle safely.........and in which situation?

Bus wire, feeder wire, other purposes?  DC versus DCC?

Rich

Alton Junction

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Posted by cacole on Thursday, November 1, 2012 8:42 AM

In order to provide a truly meaningful answer there are many factors about a piece of wire that must be taken into account.  

The Handbook of Electronic Tables and Formulas has an extensive chart for copper wire that includes eight variables that can affect capacity.

To merely say that a Cat 5 cable can handle 90 Volts max is only true at a very low Amperage and short length.

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Posted by Train Modeler on Thursday, November 1, 2012 9:09 AM

I hope our egos don't run the OP away--LOL.   

Richard

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Posted by BroadwayLion on Thursday, November 1, 2012 10:33 AM

The issue is amps not volts. For a power bus, a big fat wire is needed. LION puts 11 volts on his tracks, but has a huge 15 amp regulated power supply. 12 locomotives (8 train sets) all starting and stopping independently of each other. 14 ga wire is the minimum useful size. LION uses 18 ga feeders, but that is only because him has lotsa surplus 18 ga wire. Your cat-5 could serve as feeders, but LION uses that for Tortoise machines, signals and power relays.

LIONS are cheap... But do not go cheap on the wire, you need what you need even if something else is free. LION is also network administrator, buys cat-5e and cat-6 in 1000' spools, but is not useful for railroad.

If you have a big layout and need lots of switch motors and signals and stuff, try to get 25 pair or even 50 pair of cat-3 (telephone) cable. Commercial telephone installers will have short lengths that they cannot use, but are just right for the railroad. You can make a deal with them.

ROAR

The Route of the Broadway Lion The Largest Subway Layout in North Dakota.

Here there be cats.                                LIONS with CAMERAS

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Posted by Mark R. on Thursday, November 1, 2012 10:59 AM
It depends upon how long the wire is, and how much voltage drop you can tolerate.
AWG 24 wire has a resistance of 25.67 Ohms per 1,000 feet, or 25.67mOhms/foot.

Let's say you wanted to connect a 3A load to a battery that was 25 feet away using AWG 24 wire. You'll need two wires, one for the +12v, and one for the return, for a total of 50 feet of wire. 25.67mOhms x 50 feet = 1.2835 Ohms.

Let's figure out what the voltage drop will be across the wire.
Ohm's Law says E = IR (Voltage = Current x Resistance), so:
E = 3A x 1.2835 Ohms = 3.8505 Volts lost in (dropped across) the wiring.
You would then have 12v-3.8505v = 8.1495v across your load.

With a 3A load on AWG 24 wire, for every 13 inches of length you will lose 1/10 volt.
 
The OP's question should be - how much CURRENT will cat5 withstand. The insulation rating is the only thing that is concerned about applied voltage. Recall that most voltages are fairly low - most insulation is rated at 600 volts or less.

The wire has some resistance which causes it to get hot (dissipate power) when passing current. The voltage will be only a bit different between one end of the wire and the other, so it really doesn't play a part in figuring current capacity of the wire. One way to think about that is that if you push enough current to develop a significant voltage drop in the wire, it will get hot enough to burn open.

24 ga can only handle 577 ma at any voltage.

Remember, as the wire gauge numbers get larger, the cross section of the wire gets smaller, and it can carry less current.

Working off this chart - http://www.interfacebus.com/Copper_Wire_AWG_SIze.html.
 
Mark.

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Posted by gandydancer19 on Thursday, November 1, 2012 12:41 PM

As a practical answer, how about we just say that Cat 5 can be used for Tortoise switch machine wiring (Not twin coil switch machine types) and LED lighting?  You shouldn't use Cat 5 for anything else or you will most likely have problems.

Elmer.

The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.

(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.

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Posted by scott018 on Thursday, November 1, 2012 7:08 PM

Actually I was thinking of using it for  building lights and signals.

 

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Posted by ATLANTIC CENTRAL on Thursday, November 1, 2012 7:13 PM

"The OP's question should be - how much CURRENT will cat5 withstand."

Now we have mind readers on the forum! How cool is that?

Why are we trying guess what he wants to use the wire for?

Why are some lecturing on questions not asked?

As I stated before, I use cat 5 cable all over my layout. It is the backbone of my relay based Advanced Cab Control System with fully intergrated signals and interlocking. AGAIN, I use it for low current 24 volt control circuits, for stall switch motors and for sginals.

Oh, I forgot, most of you don't bother with signals so the only wiring you have is your DCC buss.

Maybe this guy just wants to use it for structure lighting or switch machines, or signals - WE DON"T KNOW.

Even if the insulation is rated higher, I said 50 volts because it is a common threshold seperating communication wiring from power wiring - the cable in question is communications cable.

Sheldon

    

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Posted by Mark R. on Thursday, November 1, 2012 10:34 PM

I don't believe my "lecture" was unfounded.

As I stated, cat5 wire will handle any voltage a model railroader can throw at it. The concern is how much current you are planning on pushing through it. I use it myself on my complete CTC based signalling system as well as over a thousand LED structure lights. But even at the 24 volts for the signalling system and the 12 volts for structure lighting, the current rating is well withing the limits of that fine wire.

It's not a matter of mind reading. It's knowledge that should be know before you mistakenly try to feed five amps of power to fifty bulbs at the end of it .... that is the unknown about what the OP is planning to do. The current load at the end of that wire needs to be known in order to determine if it's adequate - not the voltage you are applying to it.

If a friend of mine asked the same base opening question and all I said was "50 volts" not having a clue what he was using for, I'd feel pretty bad about not "lecturing" on the current values as well when I find he was attempting to use it as a track buss and melted a bunch of wires !

Mark.

 

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Posted by BroadwayLion on Friday, November 2, 2012 10:00 AM

I use much finer wire for lights and signals, but I only use LEDs for lighting and signals. Tungsten requires more amperage by several orders of magnitude (whatever that means) than LEDs.

For signal applications, I use wire salvaged from parallel printer cables. The older ones had 25 conductors, the newer specification has 25 pair of very fine wires. These work perfectly for signals especially since the are visible (yet to be painted) on the finished project.

LIONS gotta get wire where LIONS can.

ROAR

The Route of the Broadway Lion The Largest Subway Layout in North Dakota.

Here there be cats.                                LIONS with CAMERAS

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