Wiring a DPDT switch for DCC

[Guy Papillon]

I am rewiring my layout for DCC and I actually use a DPDT switch to kill the layout when using the programming mode on the PowerCab. The switch is actually wired with 20 awg wire like the rest of the layout. When using a 14 awg wire for the bus, do I have to rewire the DPDT switch with 14 awg wire? 

I suspect the answer to be Yes but I am so electrically dumb that I prefer to ask. 

 

[skagitrailbird]

I take it the DPDT switch is on the line coming out of the command station. To the layout it is 14g wire but to the program track is 20g. Is that correct? If so, the answer to your question depends upon how long the 20g wire run is. If 3+/- feet or less I think the 20g is fine, any longer and you probably should increase the wire size (lower guage number). I would probably increase the wire size one step for each additional 3-4' to a max of 14g unless it is a really long run.

[mfm37]

It really depends on how long the 20 ga wire is. Short runs of small diameter wire are no problem. The wire in the Powercab cord is carrying track power and I can guarantee it is not 14 ga.

 

[Guy Papillon]

So, why do I need a 14 awg wire for bus if wires between the PowerCab and the bus is of higher awg?

[richhotrain]

14 gauge wire is capable of supporting 15 amps of power.  The Power Cab has an output of just under 2 amps.  The Power Cab cable is smaller than 14 gauge wiring, perhaps 16 or 18 gauge.

I use 14 gauge wire for the bus on my NCE PH-Pro (5 amp) system. All of the feeder wires and the DPDT wiring are 22 gauge, so you will be fine using 20 gauge which is larger wire diameter than my 22 gauge.

Remember, as the wire gauge diameter increases, the AWG number gets smaller.  As the wire gauge diameter decreases, the AWG number gets higher.

Rich

[RR_Mel]

Guy Papillon

So, why do I need a 14 awg wire for bus if wires between the PowerCab and the bus is of higher awg?

 

 

 

The above answers are correct.

 

Here’s my two cents worth.

 

There is a current limiting factor in that the more current carried by the wiring the larger the diameter or cross section of the wire needs to be to prevent voltage drop.

 

There are several calculators available doing a Google Search, this is a typical calculator.

 

http://www.rapidtables.com/calc/wire/voltage-drop-calculator.htm

 

Enter your values into the calculator and it will give you your voltage loss.

 

You don’t need to use the window tagged Or enter resistivity: In this calculator.

Enter your wire size in the Enter wire diameter size: Window.

Enter DC in the Select current type: Window

Enter 12 in the Enter voltage in volts: Window

Enter the amount of your current draw (about 1 amp per locomotive) in the Enter current in amps: Window

Click on the Calculate button and the calculator will calculate the voltage drop for that size wire.

 

Ideally you need to keep your total voltage loss at 1% or less.

 

Typical average would be: 14 gauge wire 20 feet long at 12 volts with a 1 amp load the loss would be .1 volts or .83%.

 

Hope that helps.  

 

Mel

 

 

Modeling the SP in HO scale since 1951

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

[rrinker]

 Voltage drop is proportional to both wire size and length. So while 6 inches of #20 even at the full output of the PowerCab will have neglibile loss, 60 feet of it will have significant loss - so you want to use heavy wire for the bus to minimize the voltage drop, but short sections of thinner wire, such as for feeders tot he track or to connect to devices that don't have terminals big enough to accept the heavy wire are perfectly OK.

                        --Randy