14ga or 12ga...Which is more effiecient and why?

[Palmbay]

14ga or 12ga...Which is more effiecient and why?

I specifically want to know how a 12ga wire is more or less efficient than 14ga, and how that effects the electrical equipment utilizing that circuit?

I am looking for the dummy version of this answer. I am too technical to explain this to my customers so they can understand it. It needs to be factual with simple examples please.

Thank you for your help.

 

[mcclary's electrical]

Neither is more efficient. They have different resistance measurements, but neither is more efficient than the other. The wire size is proportional to the load per 310.16, not because one is more efficient than the other. I never run a bigger wire than legally required unless somebody's paying for the difference.

 

[barbeer]

I do not believe a conductor should be considered efficient or non. For arguments sake #12 has less resistance to current flow so ...............

 

[drbond24]

Not sure what you're getting at here, but I'll take a stab at it.

#12 has a lower resistance than #14 (the bigger the cable, the smaller the resistance). Therefore, slighty less energy is wasted as heat in the #12 conductor because of the lower resistance. It isn't enough to matter though. It isn't going to save anybody on their electric bill, it is just going to cost more to install becuase #12 is more expensive.

Trying to get someone to upgrade their cable size to save money on energy costs isn't a good idea if that is where you're going. As far as that goes, 500 MCM cable has a resistance that is less than 1% of the resistance of #14, but if you try to convince me to wire my house with 500 MCM I'll throw you out.

On your 2nd point, it has no effect whatsoever on the electrical equipment utilizing the circuit. All the equipment cares about is that it can suck enough juice to operate. It doesn't care about how the juice gets there.

The only time I can think of that a larger than needed cable should be installed is if voltage drop is a problem.

 

[billsnuff]

'cause it's Friday, I'll take a shot.......

'cause it's Friday, I'll take a shot.......

If, in the event of a non-paying customer or GC, etc., I would definately say my 12 ga. is more efficient. Heck, I can't even find 14 ga. shells.......:grin:

 

[Palmbay]

ok....

What is the average length of your cable run in a typical branch circuit in a residence?

What is the average, real world, load of said branch circuit. What happens when you plug in a vaccume or space heater?

I am not proposing that 12ga saves you energy. But does it have a more constant voltage with at load, does that extend the life of equipment pluged into it?

 

[mivey]

There is not a blanket answer. The size is based on the voltage drop, circuit reliability, power quality, power loss, installation cost, upgrade cost, current & future load, and supporting equipment costs. I'm sure there are other factors I've left out.

If you can limit the scope of your question, we might could venture an answer.

 

[mivey]

I specifically want to know how a 12ga wire is more or less efficient than 14ga, and how that effects the electrical equipment utilizing that circuit?

If properly sized, either one could win the analysis.

 

[mcclary's electrical]

ok....

What is the average length of your cable run in a typical branch circuit in a residence?

What is the average, real world, load of said branch circuit. What happens when you plug in a vaccume or space heater?

I am not proposing that 12ga saves you energy. But does it have a more constant voltage with at load, does that extend the life of equipment pluged into it?

You're right about the voltage drop on a big house. It's possible to drop below 3-5% vd on the end of branch circuit on the other side of a two story house, when the panel is in the basement, you could be looking at 500', but I don't think it would ever pay for itself in savings due to vd leading to increased amperage. If it EVER did pay for itself,,,it would take a very,very, very long time.

 

[celtic]

I am looking for the dummy version of this answer.
I am too technical to explain this to my customers so they can understand it.

Seriously?

You are too smart to figure it out yourself, so you figured you'd ask some dummies?


...maybe you should go find a DIY site.

 

[Palmbay]

I am not smart enough to narow the questions down.

In my home office right now I have 10A of load on a 14ga wire. When I hit the print button on the computer, the lights dim, and the computer battery picks up, and the printer resets. The printer is 6 amps. I am 30 feet from the electrical panel. This is just my example of a real world situation. Not all people have this kind of load in a room. What I am trying to pry out of everyones brain is does/will/could this kind of situation, lead to premature failure of electrical equipment? I could list lots of examples of light load and heavy load situations on branch circuits. That is not what I want. I want to know if an average branch circuit is more efficient in 14 or 12. I guess it depends on your average....Average TV, Lights and a Vacume will crate this situation.

Thank you

 

[broadgage]

Use of #12 when code would permit #14 will save energy since the voltage drop will be less, the saving is however very small in most cases.

for example if a circuit in #14 is loaded to 10 amps, and has a voltage drop of 6 volts, then clearly 60 watts is being wasted, and someone is paying for this wasted energy.
If instead the circuit was wired in #12 and still loaded to 10 amps, then the voltage drop would reduce to about 4 volts, or the loss of 40 watts.
Therefore the use of larger wire has saved about 20 watts.
If the load is continous, then 20 watts is about 175 KWH a year, which is worth from $20 to perhaps $40. In a few years this would pay for the thicker wire.

That is however an extreme case, most residential branch circuits are either very lightly loaded, or are heavily loaded for relativly few hours a year.
In such cases the saving is trivial.

In general upsizing wire beyond code requirements is worth it for substantial long hour loads, but not for most circuits.

Similar arguments apply to useing #10 when code would permit #12.

 

[mivey]

You're right about the voltage drop on a big house. It's possible to drop below 3-5% vd on the end of branch circuit on the other side of a two story house, when the panel is in the basement, you could be looking at 500', but I don't think it would ever pay for itself in savings due to vd leading to increased amperage. If it EVER did pay for itself,,,it would take a very,very, very long time.

You have to consider everything.

Consider #12-2 w/g at $3.80/ft vs #14 at $2.85/ft. With #12 you get 60% more wire for 33% more cost. #14 to #12 impedance is a 35.5% reduction. Allowable ampacity wise is the same incremental.

The 15 amp breakers are cheaper but you may need more of them with #14. The #14 is cheaper but you may make more home runs with #14.

I guess we could go on and on (just refer to other threads), but suffice it to say every situation should be evaluated on its own merits.

I have used both, based on my particular need: some economic, some not.

PS: Lest anyone wonder: I'm a 20-ampere.:grin:

 

[drbond24]

In my home office right now I have 10A of load on a 14ga wire. When I hit the print button on the computer, the lights dim, and the computer battery picks up, and the printer resets. The printer is 6 amps. I am 30 feet from the electrical panel. This is just my example of a real world situation. Not all people have this kind of load in a room. What I am trying to pry out of everyones brain is does/will/could this kind of situation, lead to premature failure of electrical equipment? I could list lots of examples of light load and heavy load situations on branch circuits. That is not what I want. I want to know if an average branch circuit is more efficient in 14 or 12. I guess it depends on your average....Average TV, Lights and a Vacume will crate this situation.

Ok, now I understand what you're asking.

It sounds like when you click 'print' the printer load is enough to sag the voltage on the circuit due to voltage drop. When you say you are 30 feet from the panel, that probably means the circuit is considerably longer than that since it has to run up and down the walls, etc., and not in a straight line. If the circuit is even 60 ft instead of 30 ft then the voltage drop is over 5%.

It is a fact that voltage sags (a.k.a. brown outs) can damage stuff. It doesn't matter if the sag is because a tree fell on a distribution line outside your house or you clicked 'print' inside the house. The potential for damage is there.

Due to the way you are asking the question, I believe #12 AWG is the answer. It takes more to overload #12 AWG and get that sag.

Does that answer the question?

 

[Palmbay]

PS: Lest anyone wonder: I'm a 20-ampere.:grin:

How would you sell? Wrap that up and put a bow on it....
What would you tell your grandmother if she was considering using 14 instead of 12?

If this was a math questions there would be 3 pages on how to calculate it 10 differnt ways.....

 

[drbond24]

If this was a math questions there would be 3 pages on how to calculate it 10 differnt ways.....

You're the one that asked for the dummy version.

 

[Palmbay]

Ok, now I understand what you're asking.

It sounds like when you click 'print' the printer load is enough to sag the voltage on the circuit due to voltage drop. When you say you are 30 feet from the panel, that probably means the circuit is considerably longer than that since it has to run up and down the walls, etc., and not in a straight line. If the circuit is even 60 ft instead of 30 ft then the voltage drop is over 5%.

It is a fact that voltage sags (a.k.a. brown outs) can damage stuff. It doesn't matter if the sag is because a tree fell on a distribution line outside your house or you clicked 'print' inside the house. The potential for damage is there.

Due to the way you are asking the question, I believe #12 AWG is the answer. It takes more to overload #12 AWG and get that sag.

Does that answer the question?

Its 30' aprox. from breaker to 1st outlet. This is the kind of answer I am looking for though. I want examples that are easy to understand and explain.

 

[LarryFine]

There's more than one way to look at it (obviously.) For example, and in no particular order:

If you have a machine that needs a larger gauge to function properly, there's no discussion; you must supply the load. I suggest a separate circuit for large loads.

If you're feeding a light bulb, the larger voltage drop of a smaller wire will reduce the overall circuit current slightly, unless you install a larger bulb to compensate.

If you're supplying an electric space heater or a water heater, the thermostat will maintain less current for a longer time, increasing overall power usage over time.


For your example, I'd recommend a dedicated circuit for the largest single load, which I'd say is the inrush current of the printer.

 

[Sierrasparky]

If you are having drops because of overloading then you need to add a circuit for the load used. In a residence it is pretty tough to plan ahead for these things.
Say if you wired the home in 12 for all the rooms. do you put each room on a seperate circuit. (maybe if it is what the customer is paying for)
Even then you could overload the room with all the entertainment stuff, computers and laser printers. Where do you stop.

 

[mivey]

If you're supplying an electric space heater or a water heater, the thermostat will maintain less current for a longer time, increasing overall power usage over time.

Hmmm, not sure I buy into that one.