[lwchris]

Is 100’ too long of a run for 12/3 romex powering 2 receptacles? It will be on a 15 amp breaker.

[Stratmando]

Should be fine, Are they for convience?
12-3 is a red, black, white and green. You could have 2 recpticles on separate circuits.
Red circuit and Black circuit, they would share neutral. MUST be on opposite phase.
12-2 has three wires, they don't count the ground, could be confusing.
12-3 has 4 wires.

[lwchris]

Yes they are for convience. On an outside circuit ran through 3/4" sch40 pvc. Would a 20amp breaker be OK? What is the max length for 12 gauge wire on a 20amp circuit. Also what would it be for a 15 amp circuit

[Stratmando]

I would put on 20 Amp,(with 12-3, you could have 2-20 Amp breakers.)2 circuits.
Or 1 circuit with 2 recpticles, and 1 switchleg for light?
You are not supposed to run romex in conduit.
Have to get formula from office, basically can't exceed 3% on branch circuit, voltage drop.
Voltage drop on feeder and branch not to exceed 5%.
With 3/4 PVC, you could easily pull in #10's if you want to reduce voltage drop, still use
20 Amp Breaker, and recpticle.
Your #12's are fine. Check in code book 210-19(Conductor-Minimum Ampacity and Size)
Good Luck.

[tkrussell]

The question, what is the maximum length for a circuit is too broad a question, these is no standard answer, since one variable is the load size.

One of the most accurate voltage drop formulas is:

2 x Length x Amps x resistance of wire / 1000 = volts dropped

However , the resistance is listed in Table 8 of the NEC for all the types and sizes of wire. #12 solid copper is 1.93 ohms per 1000 feet.

3% max Vd of 120 volts is 3.6 volts.

If a 20 amp circuit is loaded to it's max of 80%, then the calc is: 2*100*16*1.93/1000=6.2 volts dropped.

This exceeds the 3% max. The result is the load could not be larger than 8 amps to keep the Vd at 3 volts.

Without the code book, the resistance per 1000 feet of wire is not readily available, however there are several on line Vd calculators that will work fairly accurate:

Voltage Drop Calculator JavaScript

Voltage Drop Calculator

Voltage Drop Calculator

Calculating voltage drop on a certain size wire is better done by first determining the load to be served, then decide the voltage available, along with type of wire, ambient temperatures, to then chose the wire size.

Short answer is if your load at the outlets will be no larger than 8 amps, then #12 is fine, as the load increases, the voltage drop will increase above the recommended maximum of 3%, and the load may not operate properly.

if the load is only resistance, such as incandescent lamp or electric heat, then the result will only be lower light level or reduced heat, and no damage done. If the load is a motor, the motor will not operate properly and low voltage will damage the unit.

Don't bother checking Section 210.19 of the NEC, as this is even confusing to most electricians, let alone a layperson, This is where the code states the recommendation of maximum percent of voltage drop.

[lwchris]

When running #10 wires to receptacles, would you use a 12 gauge pigtail from the #10 to the terminals of the receptacles?

[tkrussell]

Yes, as the #10 will not fit well on the screw terminals of the receptacle.

[Washington1]

You are not supposed to run romex in conduit.

Not true. Code is mute on romex being ran in conduit. You can run romex in conduit.

But, Code is not mute on conduit fill

[Stratmando]

They won't let us run romex in 100' of conduit down here. They say it is a heat thing.

[Washington1]

The question is: Why would you want to run romex in conduit! I can see protecting it (sleeve) up to two feet or even 6 feet. But, I'm against running it further than that (Personal feelings). Yet, this doesn't change the code, and code is mute on running romex in conduit. I reiterate: Code is not mute on conduit fill.

Now if your jurisdiction has a set of code rules, then I'm sure it overrides the NEC. But, jurisdictional code doesn't dictate the nation.

[Stratmando]

I agree, It would be tough to pull extra wires in future if needed.
Also, I don't know whose jurisdiction you're in. If everyone around you runs their romex in conduit, it is probably? OK

[Washington1]

I can't speak on what everyone else is doing, All I can do is relay code. I said it's not against code--if you size your conduit accordingly.

Our area has adopted the NEC--in conjunction with it's own set of rules. Our State is strict!

[Stratmando]

There is no argument here, We are both right. Now, we need to figure, Does he live near you, or does he live near me, If he lives near me, he can't use aluminum either.
I think it is because we are surrounded by salt water? I have seen enough problems from trailers that were manufactured elsewhere and shipped down here. They had many problems, They don't allow them down here anymore. If they would allow, I still would not use. Don't know how aluminum works away from salt environment, I know it can only be better.

[tkrussell]

Gentlemen, please allow me to direct your attention to:

NEC Article 334 NM Cable

Section 334.15 Exposed Work (B) Protection from Physical Damage
.
Paraphrased for Brevity

"The cable shall be protected from physical damage where necessary by conduit, EMT, Sch 80 PVC, etc.. Where passing thru a floor, the cable shall be enclosed in GRC, IMC, EMT, Sch 80 PVC, conduit etc. extending at least 6 inch above the floor.

Once any conduit is used, not exceeding the 40% wire fill of that conduit shall be in effect.

Now I certainly am not advocating pulling NM through conduit of any great length. Even if the 40% fill is met, the stress and friction of the cable in the conduit will certainly damage the cable.

And, as always, ALWAYS check local city, town, county, state codes for any amendments, changes, waivers, or exceptions to the national code.

Strat, I sure can understand the aluminum issue down where you are surrounded by salt water. Here in New England, even thou we have the coast, there is no local exception to the use of aluminum, which is very popular here for large feeders, and certainly, the utility lines.

Which makes me think, does your local utility use all copper for their aerial and/or UG installations?

[rfox1973]

Should be fine, Are they for convience?
12-3 is a red, black, white and green. you could have 2 recpticles on seperate circuits.
Red circuit and Black circuit, they would share neutral. MUST be on opposite phase.
12-2 has three wires, they don't count the ground, could be confusing.
12-3 has 4 wires.

Stratmando, Your description sounds similar to a project I am trying to complete. I would like to install two outlets out by my water feature. One outlet with constant power and one controlled by a switch so that I can turn the 7 amp waterfall pump off and on as I see fit. I have a 20 amp circuit with only two outlets on it in the house with 12/2 romex connecting them currently. I would like to extend this run if possible to the water feature outlets. The total run length from the circuit breaker to the water feature outlet would be 190 feet. I was told to use 10/3 romex by my local hardware store but I am not sure how to hook it up. Any input would be greatly appreciated.

[Missouri Bound]

At that distance expect to lose approx. 8 volts. Shouldn't be a problem for lighting or a small power tool, but a large amperage tool will clearly show you the effects when you start it. And for my two cents... if I was going to take the trouble to bury conduit I would certainly pull individual conductors rather than a cable. That would give you some options in the future.