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jackwashere 02-18-2012 11:46 AM

efficiency voltage drop wire gauge
 
On the ranch there are significant distances where I want to run cable. I know wire gauge correlates with voltage drop. What I don't understand is whether or not this affects efficiency or just capacity. If the load I plan can be handled perfectly well with 12 gauge wire is there any value added to using 10 gauge wire? Will it translate into better efficiency over time? If I pay one time up front for more expensive thicker wire will I save money on power bills over time by having a more efficient system?

hawkeye11 02-18-2012 12:05 PM

Quote:

Originally Posted by jackwashere (Post 856578)
On the ranch there are significant distances where I want to run cable. I know wire gauge correlates with voltage drop. What I don't understand is whether or not this affects efficiency or just capacity. If the load I plan can be handled perfectly well with 12 gauge wire is there any value added to using 10 gauge wire? Will it translate into better efficiency over time? If I pay one time up front for more expensive thicker wire will I save money on power bills over time by having a more efficient system?

It's simply a matter of capacity. Every size wire has a different ampacity, meaning the amount of current it can conduct safely without exceeding its temperature rating.

That being said, if you install a #12 wire on a run that is too long or is too small for the load being served, you will experience a significant voltage drop in the circuit which could overheat your wires, and also cause appliances to operate improperly, motors to run hot, lights to dim, etc.

Yoyizit 02-18-2012 01:56 PM

Quote:

Originally Posted by jackwashere (Post 856578)
If I pay one time up front for more expensive thicker wire will I save money on power bills over time by having a more efficient system?

Yes. . .but. . .how much time?
#12 is 1.6 ohms/1000' and #10 is 1.0 ohms/1000' so you can figure how much power you'd save by using heavier wire, assuming you know the average current through the wire and the length of each wire. You do know the max current, though.
Depending on your elec. cost per kwh and how long you will live in the house and how much hassle it is to bend #10, if you figure you'll break even in more than 10 years I wouldn't do it, even assuming your cost/kwh stays constant.

For the 10 years, search on

investment horizon

Thadius856 02-18-2012 02:09 PM

This question was asked a while back about upsizing household circuits from 14g to 12g not for the extra 5A but to reap savings through efficiency down the road. The answer to that question was almost certainly that it's not worth it - the payback period alone was something in the range of 15 years at a constant 15A load, IIRC.

I'm interested to hear a few pro'd chime in on this one, but I'm afraid the answer will be much the same.

Yoyizit 02-18-2012 03:20 PM

There may another angle to this.

You know how when you have a summer place you feel obligated to go there because you have already paid for it?

Well, the savings for heavier only accrue with heavy current draw so you may feel a pressure to use more elec. because you put in heavy wire so you may not end up saving anything.

zappa 02-18-2012 04:35 PM

Quote:

Originally Posted by jackwashere (Post 856578)
If I pay one time up front for more expensive thicker wire will I save money on power bills over time by having a more efficient system?

Actually, it will work just the opposite. If you pay more for heavier wire you will also pay for more electricity but you will also have a more efficient electrical system. Have I confused you yet? :huh:

Take a resistive load like a lamp or heater. Since there will be more voltage drop through a smaller wire, the lamp will use less electricity, dimmer or less heat but not less efficient, and the meter will measure less power.

Motors and electronics are not so cut and dry and usually bad to run with too much voltage drop. Some will draw more current with lower voltage, some less, and this is where efficiency comes into play.

AllanJ 02-18-2012 08:33 PM

When the light bulb is receiving less voltage it is consuming fewer watts.

But the amount of light per watt not counting the watts consumed in the wires is also less.

Much of the time you don't care. But in some cases, with thinner wires and suffering more voltage drop, you might need, say, 11 light bulbs to give enough light where, had you had fatter wires and lesser voltage drop, you needed 10 light bulbs. In this example the overall power consumption with the voltage drop is significantly higher.

It is hard to predict how other kinds of equipment such as televisions or compact fluorescent lights or refrigerators or power tools will behave with reduced voltage. It is better to use the correct size wire and wire it up right to begin with.


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