Amps in a wire...

[chrisatpsu]

in my plans I'm working on for next year, I need to know how many amps i can send through either regular spt1 or spt2 wire at 12v DC.

yeah, i know the spt1 or 2 is just the insulation on the wire, but whatever your basic standard gauge wire that happens to be spt1 or 2.

and the number you're answering with, is it the max, or an 80% or 90% figure?

[t.jo13]

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[rdebolt]

As much as you can until it melts then back down a couple of amps!   


I AM just kidding!!!!   

[shaunkad]

It dependes on the length and if they are bundeled together

[chrisatpsu]

30ft maximum, and that's only if i can support a lot of amps...  single wire (2 conductor) either connected to the power connector of an active hub, or powered from a 12v power supply from Ray...

[smeighan]

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SPT 1 20 AWG is rated for7 Amps (some manufacturers say 2 amps)
SPT1 18 AWG is rated for 10 Amps
SPT2 18 AWG is rated for 10 Amps.
SPT2 16 AWG is rated for 13 Amps

[wwwgator]

Bundling cables affects only AC lines, DC- there is no derating factor ( no induced voltage from colapsing fields across parallel conductors)

Kinda raises my curiosity when someone asks "whats the max I can......."
Be safe.

[tbone321]

What is your definition of a lot of amps?  I would say that you could push 15 without much issue.  I would guess that these wires are going to be outside.

[chrisatpsu]

so for 18 AWG wire, then 20A @ 12 volts DC for a abput 20ft is a bad idea?

[chrisatpsu]

The part I have trouble wrapping my head around is...

SPT1 18 AWG is rated for 10 Amps
SPT2 18 AWG is rated for 10 Amps.

10A @ 12 volts DC is considerably less power, than say 10A @ 120 volts AC  -  one is 120 watts, one is 1200 watts.

yet the wire can only handle 10A regardless of the voltage?

[tbone321]

18 AWG for 20ft might be ok.  It may get warm but if it's outside, who cares.  You may have a bigger issue with voltage drop.  You could always set up a lenght and test it.  See how warm it gets and how much of a voltage drop you are getting.  If the wire is getting hot or the drop is unacceptable, you could always double up on the wire and zip tie them together.

[chrisatpsu]

does doubling up on the wire double my capacity?  or not quite?

[tbone321]

Yes, it will double the capacity.

[rm357]

Amps is a measure of actual electron flow. The max current is a fudge based on the cross sectional area (gauge),  reasonable heat dissipation, and the amount of voltage drop you are going to see at the end of the wire (the wire is not a perfect conductor - there is a conductance number that is calculated based on the material the wire is made of and the cross sectional area. You multiply this by the  length of the wire to figure the equivalent resistance, which can then be used to calculate the voltage drop at the end of the wire when under full load.)

To run 20 amps ~ 25 feet, I would suggest 12 gauge wire... If you are going 50 feet or more, you should up it to 10 gauge.

The great thing about using 12v systems to power our stings is that we can tolerate about a 4 to 5 volt drop in the line voltage before things start shutting down. If you are using a 5 volt system, even a 2 volt drop is gonna cause problems.

[meman]

so for 18 AWG wire, then 20A @ 12 volts DC for a abput 20ft is a bad idea?

Not at all; it's a great idea if you are building a heater.