Re: Buss wire


Mark Gurries
 

Yes using a large enough gauge wire will satisfy fault protection.  Doing a coin short circuit test will verify if a given section of track is wire sufficiently to allow fault protection.   But the very next reason above fault protection  is to make sure trains maintain a given speed consistently when you run long wires..

A 1.2V drop at 120V represents a 1% voltage drop.  No problem.  But the same 1.2V drop at 12V, is a 10% drop.  That will translate in a 10% drop in train speed.

On Mar 26, 2019, at 9:21 PM, David McBrayer <d_mcbrayer@...> wrote:

Carl, 
I take your point.  However, this is about a low voltage tabletop model railroad not the Northeast Corridor. 

Dave McBrayer


On Mar 26, 2019, at 20:18, Carl <carl.blum@...> wrote:

Hello Gang:

I wouldn't say parallel conductors is "fraught with long term reliability issues". It is done in industrial wiring when they don't want to buy or string OOO wire.  There are rules though:

1) don't put all the same conductor in one metal conduit ( induced currents )

2) each conductor needs its own circuit protection ( fuse or breaker )

3) clearly mark each conductor ( we should be doing this anyway )

The main reason for the heavy wire is for fault protection. I use heavy industrial wire, Oilflex and similar, 2mm dia.

Carl.

On 3/26/2019 5:16 PM, David McBrayer wrote:
Morgan, 
re doubling up wire. 
If you parallel two no. 20 AWG conductors, the resulting combined cross-sectional area would be approximately the same as a no. 17 AWG conductor.  
To get the approximate equivalent of a no. 14 AWG conductor you would need to parallel four no. 20 AWG conductors.  Paralleling conductors is fraught with long term reliability issues.  The issues can be managed but they are not the least expensive way to go.  

I suggest you do a web search for “wire table” to see the bigger picture of how AWG wire sizes are related.  AWG numbers have no direct relationship to cross-sectional area, which does relate to current carrying rating.  See also “metric wire table” to see how they relate.  

Yes, you can do it but be sure to notice how much hair you have (or don’t have 😉) when start troubleshooting some day down the road. 

Dave McBrayer 
Castro Valley, CA 


On Mar 26, 2019, at 12:24, PennsyNut <pennsynut@...> wrote:

I am new to this group. Just have a simple question. If a buss wire "should" be AWG14. Would two AWG 20's twisted/soldered together be sufficient. All the stuff I see is so complicated and overwhelming to me that I don't understand wires. I note that two AWG 20 gauge wires are the same size as AWG 14. And when I test with a meter, see no voltage drop with the "double twisted soldered" wires. In fact, the DC voltage and amperage is the same when tested with loco on track. I hope I'm clear, and just want clarification on wire size.
Morgan Bilbo, new to DCC

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Best Regards,

Mark Gurries
Electrical Engineer
DCC Website & NMRA DCC Clinics: www.markgurries.com



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