how far you can run 12 gauge wire on 20 amp circuit with multiple receptacle’s
derekr
| Posted in General Questions on
If it’s a 20 amp circuit it says the wire should go no more than 50 feet
Is that 50 feet per receptacle or is that 50 feet for all the receptacle’s together?
Example, running cable from the breaker box to 1 receptacle is only 28 feet then the next one is 15 feet then the next one is 15 feet etc
If I chain all of them together in this one room it will be over 100 feet, so I don’t know if the 50 foot rule is per receptacle or for the total of all the outlets on 1 circuit
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Replies
> If I chain all of them together in this one room it will be over 100 feet, so I don’t know if the 50 foot rule is per receptacle or for the total of all the outlets on 1 circuit
Where are you reading about a "50 foot rule"? Hint: it's not in the National Electric Code, if that's what you're under.
I just searched online how far you can run 12 gauge on 20 amp breaker and 50 feet came up
Yea, that's really not a good approach.
The real rule is based on volt drop. Total voltage drop for the system isn't supposed to exceed 5%, with the usual rule of thumb being volt drop in the branch circuit (which is what you're talking about here) shouldn't exceed 3%. For a 120v circuit, that means 3.6 volts of volt drop. With 12 guage wire, that works out to just under 57 feet with a full load of 20 amps. If you allow for 16 amps (the maximum CONTINUOUS loading permitted on a 20 amp circuit), you can go just shy of 71 feet. The rule is supposed to apply to the farthest point on the circuit.
Note that the code doesn't really specify how you split up the allowable 5% though. If you consider the reference point to be the main disconnect, which is probably also in your electrical panel that is feeding this branch circuit you're talking about, then all 5% of the allowable voltage drop can be allocated to the 12 gauge wiring for that circuit. Now you're good for a bit under 95 feet for 20 amps, or 118 feet for 16 amps.
The interesting thing is that this volt drop "requirement" isn't really a "requirement", it's a recommendation in the code. It's a good idea to try to follow this recommendation as much as possible though, but it's only enforceable in a few specific cases, each having other requirements (circuits for "sensitive electronics", fire pumps, etc.), none of which probably apply here. If this is going to be a standard branch circuit running general purpose receptacles in a residential setting, where the typical "load" will be a table lamp, maybe a TV, and the ocassional vacuum cleaner, then I wouldn't worry about a 100 foot run like you have here. What I would try to do is to split that run to minimize the total length of cable between the power source and any individual receptacle. You can often do this by wiring the outlets in a sort of U shape for the wiring, then feeding the U in the middle from the panel. This way you cut down on the maximum length of wire to the endpoints on the circuit, and this often works better than just making a straight run of wire and daisy chaning everything in a line.
Bill
> You can often do this by wiring the outlets in a sort of U shape for the wiring, then feeding the U in the middle from the panel. This way you cut down on the maximum length of wire to the endpoints on the circuit, and this often works better than just making a straight run of wire and daisy chaning everything in a line.
Or you could do a ring circuit like in the UK and make troubleshooting down the road extra hard. Note to the reader: don't actually do this! :-)
I've always been tempted to try this.
The first outlet from the breaker is 28 feet, all the outlets tied together are like 120 feet
I didn’t know if I was to go by the 28 foot distance for the distance rule or the 120 feet
You take the total run from the breaker in the panel to the very farthest outlet on the circuit. That's all there is to it.
As I said though, I don't think you have anything to worry about here. Try to feed the run of outlets somewhere in the middle if possible to try to cut down on total distance (that depends entirely on your floorplan layout though).
Bill
If 120 feet is fine I’ll just leave it, trying to start it in the middle is more complicated with where the room is
My tv outlet is the last outlet on the chain, could the tv not run properly if it’s 120 feet away or something?
You’ll just get more got drop with the longer run. A tv isn’t enough load to make much difference though. Higher current loads on longer runs mean more volt drop. A space heater is the largest load a typical residential circuit would ever see.
As DC mentioned below though, you can tap the feed off of any box on the run, so it’s not a big deal to split the circuit into two halves fed from the same breaker to cut down on the maximum length or wire from any outlet back to the breaker. The only time you’re really stuck with a long, straight line is when wiring outlets down a long hallway.
Bill
The 120.
Rewire it so that it's two branches instead.
Yea I just wanted 2 breakers per room, one for lights one for outlets, so if I do 2 for the outlets then I might have 3 breakers per room, seems like too much
I rather just leave it at 120
You don't have to add a breaker. Just at the first junction box have it go off in two different directions.
Deleted
I'm wondering what your scenario is that you are going 15 feet between receptacles. Maybe going up to the attic, across 6 feet, and then down to the next one? Because it's a retrofit and you don't want to open the walls to run the wire more directly? If you have attic access you could consider having a trunk line in the attic with a junction box above each receptacle, or maybe a junction box for each pair of outlets, so the current flow to the furthest receptacle is a straight line path along through the attic and then down once. You buy less wire that way too, which is expensive theses days.
I’m going up through a small attic then down, it’s a new house
I have to go up and down a lot because I’m going over 2 doors and I also have 2 windows close to the floor I was going over, I might be be able to go under them instead to save about 24 feet it would be tight though, I may try to get that to work
I don't know if there is a US equivalent to "Electrical Code Simplified" by PS Knight but it is what you need to find and read.
I have looked at an old house with DIY wiring. Once the basement ceiling was pulled it was beyond scary, every code violation you can think of was there. I'm pretty sure the people doing the work thought they were doing a proper job.
Random internet searching for house wiring is asking for trouble. I'm all about DIY but there is no way to find all the unknowns you don't know about and those are the ones that will create problems.
Akos,
A couple of decades ago I started on a renovation of a house and found the original owner/builder had wired the whole place with short scraps he had scavenged from work. There were buried marrettes everywhere, and the walls had to be taken down to the studs. The owners were livid, and blamed me for not anticipating this. They ended up stiffing me on my final draw.
I’m just running the wires, not making any connections, I’m going to have an electrician come behind me and check them and make the connections. Plus I’m going to have an inspector on top of that
he said 100 feet would be better but 120 would be fine since it’s just a bedroom, I’m not tying the 20 amp outdoor outlet to it now though
Doing half of your electric is a bad idea.
Either learn enough to do it all, or hire it out. Otherwise, you risk ending up in a finger pointing situation when something goes wrong, or worse, a liability situation when something goes really wrong.
Keep in mind that there are some restrictions on cable routing too. If you're too close to the edge of the stud, you have to use a nail plate, for example (which is to protect the wire from something being driven into it, like a drywall screw, for example).
I don't like the earlier idea someone had of using lots of junction boxes in the attic, either. Two reasons for this: the first is that all those junctions are a lot more work to install, and they're all weak spots, but also they have to be accessible per code. That "accessible" part means you can't bury them in drywall, or put them in an attic space that can't be accessed.
I would try to run the wire horizontally in the walls as much as you can to cut down on "ups and overs". Get a good wood boring auger bit (any electrical supply store will have these, but you can find them at the box stores too), which have a screw point tip to help pull them through. You'll need a beefy 1/2" drill to drive these, but they make it relatively quick to bore holes in studs to run wires. 5/8" to 3/4" are good sizes for these bits. I think my largest is 7/8", which can fit 2-3 cables if you're careful.
Bill
Yep I’m going horizontal as much as I can but it’s still going to be around 110 feet, i shortened it a little, i actually have 3 doors I have to go over then down
Will the voltage drop only occur at the last outlet or will it be over the whole run? I may start at the tv first then end it at an outlet that most likely will never be used instead
Should I use a metal plate even if it’s stapled to the side of the stud? Or are you talking about if its going through a hole in a stud
derekr,
With the exception of some dedicated outlets for appliances, it's not a good idea to anticipate what loads an outlet will end up being used for just based on what you plan on doing right now. That's why electrical codes don't typically do that.
This is a question for that electrician.
The voltage drop only will occur at the last 2 outlets right if it’s 120 feet? Or will it be over the whole run?
It depends on the load. In the simplest case, if you plug a heavy load (like a space heater) into the farthest outlet on the run, you will see the most volt drop at that outlet, but you will see proportional amounts of volt drop at every other outlet along the run. An outlet halfway along the run would see half the volt drop, etc.
If you plug a heavy load in at the middle, and a light load at the far end, you'll still see the most volt drop at the far end, but it will drop off relatively quickly as it approaches the heavy load, and then less quickly as it continues to the far outlet. Volt drop is a function of current (amps) and the resistance of the wire, so the heavier the load, the more volt drop you get between that load and the source. The same goes for longer runs of wire, which means more resistance. It's basic ohms law.
What happens when you split the run as we've been discussing, is that you cut down the max total length of wire. If, for example, you halve the length of wire on the way to that space heater, you also cut the volt drop in half. The other "side" of the half of that circuit will only see the volt drop contributed by that space heater along the common part of the cable run between the source and wherever you feed into the "halves" of the circuit. Hopefully that makes sense, a drawing would probably be more clear.
Bill
Should I do anything to protect wires that are stapled to the sides of a stud?
Seems like the drywall people could easily make a mistake and drive the screw in at an angle and hit the wire that’s on the side
You shouldn't be stabling wire to the edges of studs on walls, the wire needs to run through holes bored through the middle part of the stud. Code requires that the wire be reasonably protected from damage, so it's not supposed to be placed in areas where it is likely to get whacked/poked/cut/etc. The usual way to do this is to run through holes bored through studs or joists, and to put nail plates on the edge of the stud over the hole where the hole has to be too close to the edge of the stud.
If you can post of pic of exactly what you're talking about, I can advise what you could do to protect the wire.
Bill
I won’t be home for another 6 hrs, but it’s stapled inside the wall against the side of the stud 6 inches above the switch box right before it enters it
This is what I was told to do, i have them stapled to my studs and the floor joists for my vertical lines not the horizontal ones with hole drilling
derekr,
Maintain the same distance from the face of the stud to the edge of the wire as you would for a hole through the stud, which is 1.25".
Ok I’ll just hope the drywall people use the correct size screws and keep them straight if they don’t lol
I had thought you meant you stapled to the outside edges of the studs, which is a no-no. Stapling to the inside faces is fine, as long as you maintain spacing in from the edge as Malcolm mentioned.
The drywallers should be using screws that penetrate no more than about an inch into the studs. If they come in with boxes of really long screws, tell them to go get the right screws instead. Excessively long screws can damage wiring, pluming, anything that is run inside the wall.
Bill
For 1/2" drywall the appropriate drywall screw is 1-3/8", which penetrates 7/8" into the stud. Code is that wiring should be no closer than 1-1/2" from the face of the stud. So if everyone does their job there should be a margin of error of 5/8".
Note that a standard stud is 3-1/2", so to run a wire no closer than 1-1/2" to the edges of the stud you have to make a 1/2" hole exactly centered in the stud.
If you have to run the wire closer than that you should put a steel protective plate like this:
https://www.homedepot.com/p/Halex-1-1-2-in-x-5-in-Zinc-Plated-Steel-Nail-Plates-62850/100165368
between the stud and the drywall. The drywall guy should know that if encounters a plate like that he needs to put is screw in a different spot.
What if I have 3 or 4 wires going up 1 stud? How should I make them all 1.5 inches from the edge?
I have a light switch in the bedroom with 3 coming out, 1 is coming from the breaker, 1 is going to lights, and the last one is another hot going to the closet switch
Can I go across to the other stud or do all of them have to go up the same stud that the switch is on?
Anyone have a picture of what the correct way of this would like?
DC,
Our code up here specifies 1.25" to the edge of the hole. I guess to maybe account for 3/4" bits and wiggle room.
Standard practice if you have a lot of runs in one stud bay (such as where a large bank of light switches may be located), is to run some of the wires on one of the studs and the rest of the wires on the other. You can also use a cable support that can hold multiple cables like this one:
https://www.amazon.com/Gardner-Bender-MCS-100W-Multi-Cable-Secures/dp/B005EAFLDM/ref=mp_s_a_1_16?crid=1RG124CMURXG2&keywords=nm+cable+support&qid=1667958521&sprefix=nm+cable+supp%2Caps%2C101&sr=8-16
BTW, the standard size hole to bore to wire through studs is a 3/4” hole. You can use a 1/2” hole, but you can only run one wire in such a small hole and it’s a tighter fit, so it’s harder to pull a run of cable through multiple studs using small holes like that.
Bill