I have wire of varying sizes and was wondering if, when making up pairs of feeder wires, (or any ther place pairs are needed) if both wires need to be the same gage? For example, if I have 22 ga of one color and 18 ga of another, can they be used paired together? Could save a lot of wire purchasing if I can.
Thank you,
Richard
The max current will be the capacity of the smallest wire.
Mel
My Model Railroad
http://melvineperry.blogspot.com/
Bakersfield, California
I’m beginning to realize that aging is not for wimps.
Either gauge is adequate.
The electrons in the 18 ga wire are traveling at the speed of light. In theory so are the ones in the 22 ga wire, but if they are only half as fast, which would be 150 million meters a second, you won’t notice.
And here I thought it was the number of electrons trying to make it all the way down the wire without bumping into each other…bigger cross section less bumping for a given number of electrons.
Hello All,
OK, folks, I’ll take this one for the team…
Technically…No.
Practically…Yes.
(Deep Breath…)
First the technical: NO
Wire is a physical electrical path between point A and point B.
The capacity of a wire to safely handle the properties of a given electrical source is expressed in gauge- -think of the diameter of a water pipe.
Lower wire gauges have a greater energy capacity- -bigger pipes move more water.
The power of electricity can be expressed in many ways.
Like water, you can think of the speed of the water, the volume of the water, and the pressure of the water.
When a stream of water is compressed into a smaller diameter pipe the pressure increases.
When a stream of electrons moves from a smaller gauge to a larger gauge (thicker wire to thinner) the result is not an increase of pressure in the electrons, it is heat due to the friction created by the bottlenecked electrons.
Unless this heat is dissipated it can create a spontaneous thermal situation- -FIRE.
Second the practical: YES
You will need to determine the load, typically expressed in Amps, that you are dealing with.
The highest amperage load must not exceed the amperage rating of the smallest (highest number) gauge of the wire.
In many situations the smaller gauge (thicker) wire is used for the primary or “Hot” and the lower gauge is used for the “Neutral” and “Ground” (Note: Neutral and Ground are not the same).
When faced with the same gauge wire with different color jackets I would rather use the same gauge and stripe them with colored electrical tape than mix gauges for the same feed.
Hope this helps.
“friction from bottlenecked electrons”? Now I think I have heard it all.
The short answer is that you can happily use two different wire sizes for DC or DCC as long as you assume the load will be suitable for the smaller gauge length. Voltage drop will be less than if the whole out-and-back path were the smaller gauge, but be conservative.
The actual drift speed of a particular electron in copper metal is not very high. The ‘near light speed’ for low-voltage DC comes from the time between when an electron goes into one end of the wire, driven by a given voltage/potential difference, and a different one pops out of the other end. (And that is not practically affected by this range of wire gauge… it’s the number of electrons doing this that constitute the current.)
wouldn’t the same be true when current flowing between a power source thru a wire connected to a resistance? would there be a voltage “increase” where the wire and resistor meet?
wouldn’t the restrictive flow thru the “smaller pipe” also reduce the flow thru the larger pipe? aren’t they the same?
wouldn’t the momentary “presures increase” create a back pressure that reduces the flow thru the “larger pipe”?
Kirchoff’s Law describes the current thru and voltages across various resistive elements in a circuit.
yes there will be slight higher voltage drop across the same length of thinner than the larger gauge wire, but it’s the motor that’s limiting the current.
the amperage of the circuit is not a given. it is the result of the sum of the resistances in the circuit and voltage across them
Restricted rather than compressed. Water is not compressible for practical purposes.
Restriction in water pipes drops the pressure through the restriction relative to the pressure upstream of the restriction. Venturi effect. The pressure upstream of the restriction only rises relative the pressure in the restriction. Ultimately all the water pressure in the pipe originates from an electric pump in most municipal water systems. In my hilly town water is pumped up from the river to numerous underground storage reservoirs (huge tanks) which then gravity feed houses below them. Pipe pressure can’t rise higher than mains pressure no matter what the restriction. Houses are fitted with pressure restrictors to drop mains pressure to approximately the same safe low usable level no matter how far down the hill the house may be from the reservoir. Old fashioned water towers provide the same type of head pressure and capacity as our underground tanks. Voltage is water pressure and amperage is flow (gals/hr) in the water system analogy. Pipe friction would be ohms electrically.
Electricity is weird stuff. The analogy drawn with water flow from reservoirs through pipes to end use has to be used with due consideration for the very real differences. Pipe friction losses in water systems are real friction losses. Electrical resistance not so much, although the analogy holds true and remains useful as long as it’s not taken too literally.
Using larger gauge wire in a polarity pair makes perfect sense if you have spare wire of the larger gauge than you need. Using smaller gauge wire than you need does not make sense.
If the red wire is large enough it matters not that the black wire is even larger (or vice versa from the colour perspective). The only aspect of this that matters is the gauge of the smaller wire being adequate to purpose.
If you really have a lot of spare wire that is too light a gauge you wish to use up then simply tw
Classic!
There’s no fire hazard using #18 for one feeder and #22 for the other. There won’t be any sort of odd offset voltage or current flow.
IMO, #18 is too big for HO and WAY too big for N - #20 or #22 is about right for HO, it easily hides along the web of the rail. #20 is easily obtained at any of the big box stores neatly combined as 2 colors - it’s sold as alarm wire. It’s loosely twisted, not zip cord, so when you cut a length off, it seperates into two individual wires very easily, no crazy untwisting or anything.
For the sake of neatness and consistency, I would say get different wire and don’t do this, but it won’t fry your trains or your control system.
–Randy
considering that nickle-silver track is the equivalent of 26g wire, 1 ft of rail wire has the same resistance as 6.4ft of 18g wire. if the feeder is in the middle of two 3’ lengths of track, that last 3’ is the equivalent of ~19 ft of 18g wire.
how big a difference is there if one were 20g
g ohm/m g ohm/m ratio eq 3'
26 0.134 22 0.053 2.53 7.58
26 0.134 20 0.033 4.02 12.07
26 0.134 18 0.021 6.38 19.14
26 0.134 16 0.013 10.15 30.45
26 0.134 14 0.008 16.16 48.49
26 0.134 12 0.005 25.72 77.16
26 0.134 10 0.003 40.85 122.56
Thank you all for your responses and comments. Didn’t think there would be a problem, but as noted, electricity is weird stuff, and with decoders seemingly quite semsitive, I didn’t want to risk it.
Thanks again,
Richard