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Discussion Starter #1
I am wiring outlets in my basement and had a couple questions which are hopefully easy to answer. I am running a 20 amp circuit (12/2 romex & 20 amp breaker) that will have 11 15-amp outlets. After running the wire today I realized the run length was fairly long. I measured it and it is right about 150' of wire, which sounds like it might be a concern for voltage drop based on some quick googling. Is 150' too long and a concern for voltage drop? While Googling this question I keep getting calculators but I am not exactly sure how to calculate it or what it all means. At the end of the run is going to be my entertainment center area with TV, Blu-ray player, soundbar, etc.

Below is a rough drawing of the wire run. The dotted red line is what I have currently. If distance is too long, then I was wondering if I could/should put a junction box where the power source comes into the room and run the outlets in two different directions, shown by the blue dotted lines. The solid circles indicate where the run would end. The solid red line is the wire I would remove to make the blue dotted line possible. Looking for any recommendations.

644244


Thanks!
 

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You absolutely can put in a junction box and split the circuit. A couple things to keep in mind is that the junction box needs to be accessible, and it needs to be sized appropriately for the wire size. If you don't put a receptacle in the box, that shouldn't be a problem. But you can also split the circuit at one of the outlets, if you wanted. If you did that, do the box size calculations to make sure the box is large enough with three 12 ga. conductors, three grounds and the receptacle. You'd probably need a 22 cu. in. box if you connect everything with a duplex receptacle.
 

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Discussion Starter #3
You absolutely can put in a junction box and split the circuit. A couple things to keep in mind is that the junction box needs to be accessible, and it needs to be sized appropriately for the wire size. If you don't put a receptacle in the box, that shouldn't be a problem. But you can also split the circuit at one of the outlets, if you wanted. If you did that, do the box size calculations to make sure the box is large enough with three 12 ga. conductors, three grounds and the receptacle. You'd probably need a 22 cu. in. box if you connect everything with a duplex receptacle.
I appreciate the response. I can put the junction box in the ceiling of an unfinished utility room, so access isnt an issue. For the junction box, do I just connect the three conducters, three neutrals, and three grounds together with wire nuts? For some reason I have always thought of outlet runs needing to be linear. Surprisingly I havent been able to find any simple diagrams for this online.
 

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The best way to hook up an outlet is with pig tails. So in your case, you'd do as you say, hook up the three hots, the three neutrals, and the three grounds. Then, you would cut 6 in. or so piece of hot, neutral, and ground that would connect to the correct spot on the outlet, and then include them in underneath the wire nuts or other wire connectors. So each wire nut would be connecting four wires.

This way, if one outlet fails, it doesn't knock out the whole chain. It also allows for less voltage drop across the circuit than daisy chaining each outlet as you suggest ("linear").

I've included a picture that I hope helps. The only difference in your case is you'd have four wires of each (the three main lines and the pig tail).

Hope this makes sense!
 

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Running 16A (which is all you should ever plan to run on a 20A circuit) I would expect 7% voltage drop at 150'.

In Canada you can't exceed 3% (based on that same 80%-of-breaker-trip I assumed above). In the USA we have freedom to flex that to our requirements, application and tastes... and I strongly encourage people to do so... but 7% is high even for my tastes.

65' will put you at 3%. Somewhat further, I wouldn't worry about it. Given that your panel is in the middle, just go both ways out of it, that will be fine.


I would preserve the red run, and delete the run along the far wall. That should keep distances sane.
 

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If possible, I would run a separate circuit for the entertainment center (12 or 14) to help on voltage swings when using the other receptacles. An isolated circuit helps reduce interference.
I also would go from 2 directions on the other receptacles.
 

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Discussion Starter #7
If possible, I would run a separate circuit for the entertainment center (12 or 14) to help on voltage swings when using the other receptacles. An isolated circuit helps reduce interference.
I also would go from 2 directions on the other receptacles.
It is possible to do another circuit, although I was hoping to avoid that as I want to leave my last two open breaker spots for a future garage heater at some point.
 

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Discussion Starter #8
Running 16A (which is all you should ever plan to run on a 20A circuit) I would expect 7% voltage drop at 150'.

In Canada you can't exceed 3% (based on that same 80%-of-breaker-trip I assumed above). In the USA we have freedom to flex that to our requirements, application and tastes... and I strongly encourage people to do so... but 7% is high even for my tastes.

65' will put you at 3%. Somewhat further, I wouldn't worry about it. Given that your panel is in the middle, just go both ways out of it, that will be fine.


I would preserve the red run, and delete the run along the far wall. That should keep distances sane.

When you say go both ways out of the panel are you saying to run one power source into the room from the panel and split it using a junction box (like the blue dotted lines)? Or are you saying to run two separate circuits?
 

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Discussion Starter #9
The best way to hook up an outlet is with pig tails. So in your case, you'd do as you say, hook up the three hots, the three neutrals, and the three grounds. Then, you would cut 6 in. or so piece of hot, neutral, and ground that would connect to the correct spot on the outlet, and then include them in underneath the wire nuts or other wire connectors. So each wire nut would be connecting four wires.

This way, if one outlet fails, it doesn't knock out the whole chain. It also allows for less voltage drop across the circuit than daisy chaining each outlet as you suggest ("linear").

I've included a picture that I hope helps. The only difference in your case is you'd have four wires of each (the three main lines and the pig tail).

Hope this makes sense!
Thanks for providing the image and info. Just to be clear, if I was going to do it in a junction box instead of at an outlet, I would just bring in three wires (two "branches" and power source) and connect the three hots, neutrals, and grounds, correct? It would be easier and more efficient for me to do it in a junction box due to where the power source comes in and where the first outlets are in either direction. If I did this does this resolve the length of run concern because each of the "branches" are shorter? Or is it all the same because the entire circuit still has the same total length of wire.
 

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If I did this does this resolve the length of run concern because each of the "branches" are shorter?
That's correct, it's better. Each individual branch length will have it's own voltage drop, smaller than if they would be added together (voltage drop is proportional with the length of the wire). That drop will be added to the common portion voltage drop.
The energy code indeed requires that branch circuits to be kept below 3%, but I won't worry too much. Equipment works at -10%, sometimes the house voltage is higher than 120V...

Also the NEC requires to consider 180W load for each general use receptacle (or the actual load if you know it, like a refrigerator). For 11 outlets that makes a total of 1980W.
A 20 A circuit breaker is allowed to have only 16A load, that makes 1920W... So, looks like you are one receptacle over that limit.
 

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The 3% voltage drop is only a suggestion in the NEC, not a requirement. A 20 amp circuit breaker can be loaded to 20 amp as long as it is not a continuous load. You can have as many general purpose receptacles on a circuit as you wish.
 

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While the 20 amp circuit should not carry a continuous load of over 16 amps, the full 20 amps may be drawn particularly for appliances such as a vacuum cleaner or a band saw or a refrigerator that may have a spike of higher draw at startup. Voltage drop in the circuit will be a little hgiher at the moment of 20 amp draw compared with during say 16 amp draw. And the sensitivity of the appliance in terms of pooer performance is greatest when it needs the additional power.


So it is still desirable to compute on the desired maximum 4% or whatever voltage drop and select wire sizing based on the full 20 amps. You don't know what else may be turned on using the same circuit when the vacuum cleaner is switched on or the refrigerator starts up.


Three percent voltage drop from main panel to receptacle is suggested because there may be more voltage drop elsewhere such as form pole transformer to main panel. If there were 3% drop for the latter and you chose 4% from panel to receptacle, you are already up to 7% voltage drop when the appliance is trying to start up.


You may need to turn your head sideways to visualize the picture the way I do but I see your red line as shaped like a question mark with power coming in at the bottom. The blue line suggests to me a Y also with power coming in at the bottom. The worst case distance is greater with the question mark shape so changing to the Y shape, all other things being equal, will lessen the worst case voltage drop.
 

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You can have as many general purpose receptacles on a circuit as you wish.
NEC 220.14(I) says to calculate 180VA for each yoke of those. Yes, that was excluded to be applied for single-use residencies, but, IMO, as a good practice, you can't have "as many as you wish". NEC is not a design manual, it's the minimum safe requirement.
 

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Discussion Starter #14
Thanks guys. After thinking about it more and reading through these responses I am leaning towards splitting it into two separate circuits on different breakers. I wanted to preserve my last two breaker box openings for a 240v garage heater in the future but I think I found a different workaround for that issue.
 

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What are you intending to run on this circuit? The circuit itself does not cause an issue. However if you are intending to put some large loads at the far end it could be an issue.
 

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NEC 220.14(I) says to calculate 180VA for each yoke of those. Yes, that was excluded to be applied for single-use residencies, but, IMO, as a good practice, you can't have "as many as you wish". NEC is not a design manual, it's the minimum safe requirement.
The 180 VA is used for service and feeder calculations not individual branch circuits. Although poor practice you can have any number of receptacles on a circuit.
 

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The 180 VA is used for service and feeder calculations not individual branch circuits. Although poor practice you can have any number of receptacles on a circuit.
Just as the 180 volt amperes per outlet does not impose a limitation of the number of receptacles on a circuit in single family residences it also does not apply in service nor feeder calculations in the United States. In the US National Electric Code the service and feeder calculations of Single family homes are done using the square footage of the floor area of the house.

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I'd run #12/3 for two circuits. 15A breaker due to distance.
 

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When you say go both ways out of the panel are you saying to run one power source into the room from the panel and split it using a junction box (like the blue dotted lines)? Or are you saying to run two separate circuits?
Circuits don't have to be a linear string. They can actually be any sort of "tree" topology. As long as the cables aren't making a loop, you can pop a branch off at any junction box if you have the cubic inches to spare.

I am saying branch at the panel. Send a romex off to the left. Send another Romex off to the right. Land their neutrals on the neutral bar. Join their hots with a wirenut , with a pigtail. The pigtail goes to the breaker. 2 Romexes on one breaker. Nothing wrong with that!

Thanks guys. After thinking about it more and reading through these responses I am leaning towards splitting it into two separate circuits on different breakers. I wanted to preserve my last two breaker box openings for a 240v garage heater in the future but I think I found a different workaround for that issue.
Last two openings!?? Hold the phone!

Save your last two openings for a 30-space subpanel. We have an endless parade of askers going "Help, I'm out of breaker spaces" and that is a very cheap problem to solve at panel purchase time, since more breaker spaces are maybe a buck or two each.

You should never be out of breaker spaces, and should never have to sweat only having a few left. Electricity does our bidding. We're the boss of it. If you want to add an EVSE you ought to be able (assuming the load calc supports that). If son keeps tripping breaker because of huge gaming PC and daughter's curler, you oughta be able to throw in another circuit.

On a very long house like yours, I would actually put the sub at the other end of the house so you don't have so many 70' wiring runs. Probably save enough on branch circuit cable to pay for the sub, not that they cost enough to even care about.



The 180 VA is used for service and feeder calculations not individual branch circuits. Although poor practice you can have any number of receptacles on a circuit.
To some extent I think it depends on what you're doing. If a cell phone store wants 40 receptacles on a circuit, they're gonna plug cell phone chargers in it. Not worried about it LOL.
 
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