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-   -   Saving money by using 12 AWG on 15amp circuits? (http://www.diychatroom.com/f18/saving-money-using-12-awg-15amp-circuits-113133/)

thebrandnewguy 08-06-2011 09:41 AM

Saving money by using 12 AWG on 15amp circuits?
 
Would it be cost effective to use 12/2 wire to run 15amp circuits?

I read that using 12/2 wire instead of 14/2 wire on a 15amp circuit will reduce the energy loss from voltage drop over the distance travled. A 2% voltage drop

The book gives the example of 200 ft carrying 120volts on 14 AWG will drop 8 volts, with 12 AWG the loss would only be 3 volts. and then adds this "The apparent savings in initial cost by using undersize wire is soon offset by the cost of power wasted in the wires and by the reduction in efficiency of lamps, motors and so on."

the book is "Wiring Simplified" by H.P Richter

a7ecorsair 08-06-2011 09:52 AM

Not to dispute Mr. Richter, I like his books, but there is some truth in this. Anytime you have resistance to current flow there is some heat buildup. Heat buildup is power used. A typical residential 15A circuit rarely runs at full capacity so it would be difficult to determine the cost effectiveness of running #12 instead of #14.

AllanJ 08-06-2011 10:48 AM

In a few locatiosn you would need larger outlet boxes and junction boxes because fewer #12 conductors can go into the box compared with using #14 conductors.

J. V. 08-06-2011 11:11 AM

Tom Henry one of the most respected NEC teachers is also on board with the use of larger conductors, but warns the minimal savings may not ever be worth the extra cost in materials.
I for one use #12 everywhere in my house. But if I had to wire your house you would get #14 wherever I was allowed to use it. It would not be cost effective for me to use #12 when other contractors are quoting the job with #14. I would loose the bid ever time.

AandPDan 08-06-2011 11:12 AM

Interesting post.

If you're running 12 gauge, why not put in 20 amp circuits to begin with? Then you have the extra ampacity and at the same load, as in the 15 amp example, only lose the same amount of power and efficiency?

thebrandnewguy 08-06-2011 11:16 AM

if you put 12 all in your house, why wouldn't you recommend it for mine?

SD515 08-06-2011 11:21 AM

Difference in cost of materials, especially if you are bid competing.

Speedy Petey 08-06-2011 11:23 AM

Quote:

Originally Posted by thebrandnewguy (Post 701600)
if you put 12 all in your house, why wouldn't you recommend it for mine?

I wouldn't.
#14 is FINE for residential lighting circuits and is MUCH easier to work with, especially in multi-gang boxes.


The minute potential cost savings will NEVER been seen nor felt in a typical residential setting. Who ever says it would "soon be realized" is crazy.
Yup, I said it.

Also, in a typical home it would not matter if the breaker were 15 or 20 with regard to this scenario. The load has NO idea what size breaker it is on until it trips. So WHY bother wasting a potential 5 amps worth of circuit ampacity???

Thadius856 08-06-2011 11:24 AM

He meant that if he were doing it for hire, he'd be underbid by other electricians bidding at the rate for 14g materials. If you wanted to pay the premium, I'm sure he'd do it for you.

I'm wondering the same question... if going 12g, why not just use a 20 amp breaker? You'd get the same efficiency as if you'd used a 15 amp breaker, until you passed 15 amps draw (obviously), from what I can tell.

Edit: Wow. Too slow! :D

Olsy 08-06-2011 11:52 AM

At .07 per kwh for electricity youre only looking at a savings of like $6 for an entire year if you run a light for 8 hours a day...not worth it unless its for a vacuum that draws 12 Amps 24 hours a day for a year

Daniel Holzman 08-06-2011 12:01 PM

Got to know your kilowatt hour cost. I live in Massachusetts, which I believe has the highest electric rates in the country, at close to 20 cents per kilowatt hour. At that rate, there are a number of seemingly insignificant techniques that actually save real money, for example using all CFL or LED lights, installing a heat pump water heater rather than a conventional electric water heater, using 12 gage wire for your circuits, and buying energy efficient appliances like refrigerators, electric ovens, freezers etc. Many of these ideas make no financial sense if you are paying 5 cents per kwh, but they sure make a difference up here.

I used to pay close to $200 per month for electric, now I pay less than $175, and I used to have oil fired hot water supply, now I have an electric heat pump water heater, so the savings are close to $750 per year overall.

Olsy 08-06-2011 12:03 PM

Quote:

Originally Posted by Daniel Holzman
Got to know your kilowatt hour cost. I live in Massachusetts, which I believe has the highest electric rates in the country, at close to 20 cents per kilowatt hour. At that rate, there are a number of seemingly insignificant techniques that actually save real money, for example using all CFL or LED lights, installing a heat pump water heater rather than a conventional electric water heater, using 12 gage wire for your circuits, and buying energy efficient appliances like refrigerators, electric ovens, freezers etc. Many of these ideas make no financial sense if you are paying 5 cents per kwh, but they sure make a difference up here.

I used to pay close to $200 per month for electric, now I pay less than $175, and I used to have oil fired hot water supply, now I have an electric heat pump water heater, so the savings are close to $750 per year overall.

Wow thats crazy expensive, in alberta we pay anywhere from 5 to 8 cents per kwh

outspoken 04-29-2012 09:31 AM

Quote:

Originally Posted by Speedy Petey (Post 701605)
Also, in a typical home it would not matter if the breaker were 15 or 20 with regard to this scenario. The load has NO idea what size breaker it is on until it trips. So WHY bother wasting a potential 5 amps worth of circuit ampacity???

The reason to use 20amp would be to prevent the potential trip. There is no "waste" as it's never used until needed. Since the subject of cost was mentioned, there is no difference in price for my square-d single pole circuits.

I use 20amp because it is not uncommon for me to exceed 15amp on any given circuit due to electronics in almost every room in addition to lighting and other accessories (microwave, heaters, etc).

Jim Port 04-29-2012 09:41 AM

Sounds like the circuits were not laid out properly and in consideration of the expected loads.

a7ecorsair 04-29-2012 09:44 AM

Ah ha, another year old post resurrected:laughing:


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