Simple question, wires in parallel. How much current gain? If any?

[wfojonny]

In theory, and in practice.
I am running 110 AC current through some number 12 wire. Number twelve is not adequate.
I can easily double up on the wires. Run two number 12 wires in parallel. Same gauge, same length.
Question, what does this gain me?
Does this double my load carrying capacity? Or no?
How does the math work?
Jon

 

[MikeHalloran]

110AC is the voltage, which tells you indirectly how much insulation you need. It doesn't tell you how fat the conductor must be.

Number 12 wire, as used in houses and such, can safely carry 20 amperes at 110 volts AC. Number 12 wire can also 20 amperes at 12 to 14 volts DC, as in a car.

But the same wire is not suitable for both. House wire is normally solid, i.e. a single conductor. It bends, and stays bent.
Car wire is normally stranded, i.e., made of 7 or 19 or more smaller conductors, all twisted together, because it's more flexible, and resistant to vibration.

All of that is tangential, really. After you read up a little on basic electricity, your next step is to find out what your actual load is, by measuring (or looking up) the current required in amperes, or the power required in watts.

Back to not actually answering your questions...
How do you know that "Number twelve is not adequate."? Is the load not working right? Is the wire getting hot?


Mike Halloran
Pembroke Pines, FL, USA

 

[wfojonny]

Thank you Mike,
Wire is getting warmer than I like. Not hot, but warm enough to worry me.
Just not sure if doubling the wire doubles the capacity. As I would think, at face value.
Is there any black magic at work here?

 

[Skogsgurra]

If you mean 110 A AC, then the #12 wire cannot be used. Two #12 wires will also not be sufficient.

A general answer is that you can double the current carrying capacitiy by doubling the number of wires. Depending on code (NEC, EU etcetera) you have to consider different fusing arrangements. So you cannot just double the number of wires. There's usually more to it.

But, as Mike says, is it the voltage or the current that is a problem? You cannot get an answer without telling us what the problem is.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[waross]

There is in some of the more advanced jurisdictions a pesky little annoyance called an electrical code. Some electrical codes prohibit running #12 wires in parallel to increase current carrying capacity. One of the downsides of ignoring those pesky codes is that some insurance companies will void the insurance on your home if it is found that you installed wiring in contravention of said codes.
Hire an expert.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[wfojonny]

No problem with the voltage, simple 110 AC. The load is a fan motor, needs about 10 amps. Maybe I am stretching the wire a bit far, at 150 feet.
The fan runs okay, just worried about the wire running a bit warm.
Not too concerned with the codes here in Moose Snort, just trying to understand the theory.
If doubling the wire does indeed double the capacity, I have my answer.
What say the gallery?
Thanks,
Jon

 

[davidbeach]

Define hot. The lowest insulation rating is good for 60C. That is far hotter than you'll ever want to touch.

In the NEC applies, you have to just use a larger wire size until you get to 2/0 or beyond. Then you can begin to parallel wires.

 

[wfojonny]

Not hot.
Warm is what I am dealing with. Not more than 120f or so.
I do not wish to get much past ambient.
Does anyone understand the math? What (if anything) do I gain by doubling up and running parallel?
Is there any "path of least resistance" to factor in? Or similar principals?
Jon

 

[Skogsgurra]

Yes. We understand the math pretty well.

In this particular case, the math even has a name: Ohm's Law.

Then, there's another piece of math named Thevenin's theorem.

Want more math? What about Kirchoff's laws?

Look them up on the net and apply them. Or, you could talk to your 'principals'

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[itsmoked]

I suspect that a fan on the end of 150 feet of 'warm wire' is not working correctly. Spinning perhaps, but certainly not working correctly.

With the fan ON you or your electrician should measure the voltage at the FAN. If it's less than about 108VAC the motor is suffering.

Since it's against the regs we work by around here we're not going to tell you to parallel some #12s up.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[resqcapt19]

10 amps at 150' on #12 should give you a voltage drop of about 5 volts. While higher than I would like to see, the fan should work fine.

 

[jghrist]

As indicated by others, NEC does not allow paralleling #12 for added ampacity. If you don't need to follow the code, then you do get added ampacity, but unless the wires are far apart, you don't double the ampacity.

Ampacity is determined by how much current will cause the conductor to heat (by I²R losses) to the limiting temperature of the insulation. Mutual heating of the wires will reduce the ampacity.