One box 2 circuits

[Perfectstranger]

I have started planning my wiring and before getting to crazy I have what may be a stupid question. I will have 2 duplex outlets in a box every 8 feet or so. I want the 2 outlets in the same box to be on separate circuits. That way if I need to plug in two high demand things at the same time with out running an extension cord. Is this code? Can it be done? Is it the good idea I think it is?

 

[sberry]

How big is the building? I used 2 circuits the other day in the same area abut they didn't come from the same box or need to.

 

[Perfectstranger]

Building is 2 story 26x30. There is a sub panel that both circuits will come from. Then run to the same gang box. That way if I need to use two high draw items at the same time I don have to run an extension cord or worry about tripping a breaker.

 

[Moto]

It is a good idea.

Cheapest way is to do a multi-wire circuit. Basically, two breakers sharing neutral and ground wires. There is cable made for doing that with two hots, one neutral, and one ground.

Or they could be two separate circuits using two cables.

 

[Tim C]

That's how I set my 24x30 shop up with two separate cable runs to each box. Plus each wall of the shop is separate, so I have 6 circuits total (left, right, and rear wall each with a left and right outlet circuit). That's extreme overkill, but it's not uncommon when my friends and I are building a wheeling rig or race car to have someone grinding, running a plasma cutter, a chop saw, etc at the same exact time. This way if you plug into different walls or sockets in the same box there's no problem.

The old shop I worked from before I built this one was a 24x24 behind my Grandma's house. Every outlet in the building was on the same breaker along with the overhead lights. After tripping through the dark nearly every night to find the breaker box I said I'd never have that problem again.

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[Perfectstranger]

Thank you, I just didn't want to spend a bunch of time drawing something up and have it not be right.

 

[wyliesdiesels]

perfectly fine to do

 

[Daedalus]

Allowed by the NEC, but not by all local codes within the US. I don't know about Canada.

What I don't understand is why each hot wire is allowed to carry x amps of current, but the single neutral is allowed to carry 2x amps of current, the current carried simultaneously by both hot wires.

 

[Norcal]

The only problem is that GFCI protection is required, but can be overcome by using a 2- pole GFCI circuit breaker, expensive though. The disadvantage is that if the breaker trips both go down, not wiring the circuit as a multi-wire is another solution.

 

[sberry]

This sounds like a great idea but you don't need it and won't use it. I agree about keeping lights off of recepts. how many times you figure a bunch of pals gonna hover around an outlet and cut and chop in each others lap? What I would find useful is about 4 circuits. si a there will be doors basically 3 sides, circuit for each incl bench and another one for parasitic stuff. Walls are different as is bench.
I got bud with 2, one for everything parasitic and the other for tools and he has a lot of stuff.
This is part of load calc, realistic view of how much is needed and some experience to see how things turn out. This makes gfci easy, keeps a circuit to a box, let's one simply reach to bench or other wall if it actually happens.

 

[sberry]

An ideal situation would have a method to get in to the panel if a guy comes up with something he needed a dedicated for vvs leaving 6 circuits pparked i where 1 would do.

 

[sberry]

I wired my buds garage 30 yrs ago, 2 men worked for 20 yrs in 30x40 on 2 general's and never a trip. Only time i have seen problems is spec built with the 15 garage circuit. If there ever was a place for a law there would be it.

 

[sberry]

As for mwbc, great idea for kitchen counter tops with 80 or 100 ft circuits, ok in my storage with 120 ft of wire on some (wired with 6 where 2 would have been sufficient and wouldn't do it again) but adds confusion in small garages where it doesn't help anyway.
If I had 120v comp and welder would make provisions for them with simple circuit, breaker wire to outlet but I wouldn't pack every box in the place with snot you will never use just in case.

 

[woodzy]

I have three rooms about the same size in my shop, and all are wired like this - I didn't see a reason for two circuits at every place but there are 4 in each room.

 

[bczygan]

As for mwbc, great idea for kitchen counter tops with 80 or 100 ft circuits, ok in my storage with 120 ft of wire on some (wired with 6 where 2 would have been sufficient and wouldn't do it again) but adds confusion in small garages where it doesn't help anyway.
If I had 120v comp and welder would make provisions for them with simple circuit, breaker wire to outlet but I wouldn't pack every box in the place with snot you will never use just in case.

With THAT kind of thinking, how are we ever going to be able to claim we have the biggest baddest electrical setup?

Remember that those with the most outlets and those with the most circuits win. And my panel is bigger than your panel!

Common sense has no bearing here!


Bill

 

[Perfectstranger]

Thanks guys, I am going to rethink this. Building is exposed wood framing inside. 100 amp service, I was thinking that in terms of finishing I should
1) run wires
2)run plumbing
3)run HVAC
4)run air lines/dust collection

Is this correct?

 

[bczygan]

Thanks guys, I am going to rethink this. Building is exposed wood framing inside. 100 amp service, I was thinking that in terms of finishing I should
1) run wires
2)run plumbing
3)run HVAC
4)run air lines/dust collection

Is this correct?

A few questions, since this is an actual project, not just theoretical.

Commercial or residential building?

What size and what are the uses? What layout of equipment?

Photos? We love photos!

There is a lot of help available on this forum, in all areas.

Bill

EDIT: I just found your building thread. I'll go over there and get up to date.

 

[Orionrising]

I did a dual 20 amp ring with a whit and black outlet in each. Was overkill for a woodshop even probably. But I can plug in dust collector and tool next to each other anywhere on that wall


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[bczygan]

OK,
Had a look see over there.

Best advice I can give, is to plan your work and work your plan. Don't just go putting outlets everywhere helter-skelter.

First question. Is this outbuilding considered living space...or any part of it? If so, typical building codes have rules for general purpose outlets that typically has them spaced a max. of 12' apart.

But in any case, I would take the time to lay out how I am going to use the spaces. Plan where machines will go and plan the upstairs too.

Then you can locate the lighting and power where it really needs to be.

BTW, VERY nice spread!

Bill

 

[bczygan]

I did a dual 20 amp ring with a whit and black outlet in each. Was overkill for a woodshop even probably. But I can plug in dust collector and tool next to each other anywhere on that wall


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Wow! Impressive!

I'm just trying to figure out how I would even be able to get enough pieces of equipment or machines, into that area, to use all those outlets.

And this coming from a guy who has 8 duplex receptacles and 4 12 outlet plug strips in a 10 x 20 garage.

Sometimes too much is really just too much.

Bill

 

[Orionrising]

Wow! Impressive!

I'm just trying to figure out how I would even be able to get enough pieces of equipment or machines, into that area, to use all those outlets.

And this coming from a guy who has 8 duplex receptacles and 4 12 outlet plug strips in a 10 x 20 garage.

Sometimes too much is really just too much.

Bill

The quads are actually 3 feet apart the boxes in between are home runs mostly not hooked up for future 240 etc and this provided for the side walls of the shop as well as I did not want to open the drywall. Half the boxes are point back to the garages side of the wall. I have been happy so far. End up like this slot. Table saw dust collector lathe and jointer all plugged in at once.

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[rjkobbeman]

It is a good idea.

Cheapest way is to do a multi-wire circuit. Basically, two breakers sharing neutral and ground wires. There is cable made for doing that with two hots, one neutral, and one ground.

Or they could be two separate circuits using two cables.

What you describe is commonly referred to as an "Edison" circuit. Multi-wire circuit is, I believe, the correct term though.

How it works is, you use 3-wire (12/3 with ground for example) and run two hots. Each hot must be on different legs. This means 240 volts measured across the hots. One hot goes to one circuit. The other hot goes to the other circuit. Neutral and ground is shared by both circuits.

The catch is, some/most/all arc fault breakers don't work with shared neutrals. As long as you don't need those breakers, what I describe is good to go. Nothing against code either.

It is a common method to do what you want.


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[sberry]

There is nothing wrong with that. There is nothing wrong with an air outlet every 4 ft either but as I said I got a Bud who has all this and runs it with pretty much 1 circuit, actually 2 but still uses mostly 1. But the dust collector is good excuse to add another one, nothing wrong with that.
What I learned from doing it is that we don't need it and that is the only difference. For the guy that puts na couple 4 extra circuits and all in, not likely to be a deal breaker. If economy is of concern you can do the same thing with a lot less. The actual demand is 1 or 2 machines. Even in my shop, 1 tool at a time,,, if that. I don't think I used a corded tool all day today, not over yet though.

 

[sberry]

My shop was actually wired more efficient than my storage. I did it as I went. Had a plan on storage

 

[R.Anderson]

Nothing wrong with two circuits in the same box as long as both circuits are feed from the same panel.

It is a good idea.

Cheapest way is to do a multi-wire circuit. Basically, two breakers sharing neutral and ground wires. There is cable made for doing that with two hots, one neutral, and one ground.

Or they could be two separate circuits using two cables.

In order to share the same neutral the breaker needs to be a double pole.

Allowed by the NEC, but not by all local codes within the US. I don't know about Canada.

What I don't understand is why each hot wire is allowed to carry x amps of current, but the single neutral is allowed to carry 2x amps of current, the current carried simultaneously by both hot wires.

It is not 2x the current and it is not simultaneously by both hot wires when you share the neutral with a double pole breaker. (HINT: sine wave) It could be if you use two separate breakers that tie into the same line. This is why using two breakers is not allowed in sharing the same neutral.

 

[Cmreschke]

As has been stated above, you need a handle tie for the breakers. What has been incorrectly stated (or assumed by me ) is that if you don't share your neutral then your a o k. You DO still need a handle tie in that scenario as well.

 

[R.Anderson]

Just saw the words sub panel. Seen a few places where boxes were feed from a main and a sub also one place where a box was feed from two main panels (strip mall with a lot of hack work) Good point out none the less.

 

[Cmreschke]

Jeremy I agree with the above 100% your first post however is what I was commenting about, with regards to cutting the bar on the duplex. Others then took the ball and ran with it and that's where my comment was directed. The implication was (from my reading the whole thread) that as long as it's not sharing a neutral no handle tie was needed. Not always true.

 

[Cmreschke]

Also what I thought I read in the op was a single gang box duplex, 2 ckts. My dyslexia taking over.

 

[sberry]

Like I said, skip all this **** in a building aint no bigger than a storage shed. The demand calc is so far out there he wont use 10% of this.

 

[Perfectstranger]

I really appreciate all the input and have actually started THINKING about this. This board can be dangerous after looking at all the great garages, a guy could start day dreaming and shoot from the hip.

 

[sberry]

I done this all my life, worked in dozens of shops and wired a couple dozen garages. The need for this is wayyyyyyyyyyyyyyyyyyyyyyyyyyyy overblown. My neighbor who is a master and can have it any way he wants and for near free didn't and doesn't do this, he has a couple circuits in his garage.
This is a bit different than true dedicated equipment or stuff that comes on automatically and not a bad idea to provide circuits for furnace etc But to confuse all this when simple will do just as good or better is simply mental ************ aided from some grease from other compulsive types, many of these are actual experts, this is a different issue than getting good advice.

 

[Bigbandguy]

In the areas where two sides of the 240 are not allowed in the same room it probably goes back to the early days of electric wiring. My dad wired houses starting from the knob and tube days. He was later a POCO supervisor and spent his entire working life in the field . He said that in the very early days they lost a housewife a year who was running a vac plugged into one circuit grabbing a lamp plugged into the other. In both cases the hot side of the circuit ended up in the lamp or vac frame way before grounded appliances. The unsuspecting housewife would get across 220 (now 240) volts and that was it. He had quite a few tales from the early days. He worked for a town generating plant on a small creek before the statewide POCO even existed.

 

[sberry]

there are places it's good, I use mwbc on occasion. I just did one I did not as I wanted gfci to feed. It cost me 1 wire fill but came in under with another mwbc for lights. It split in a jobs where it wasn't even with the devices and can't remember if I pinned breakersmmm but the line is off any device or fixtures.

 

[sberry]

used one a while back in kitchen addition, ran 1 long cable and as I mention use them in some piped systems. There isn't big advantages with cable and short runs. I wouldn't want to give up simple, all single pole breakers is a good thing in residential.
Easy to gfci this way.

 

[sberry]

I been learning my phone and forget I had a camera. I should have snapped a panel at a church. The last guy that reworked it was a master. The handyman were not sure what they were looking at with some wire sizes/breaker matches in some places. if they would have looked downstream would hand seen 14 wire , the guy used 12/3 to get out of a congested panel, prolly what he had too, left some breakers, used some tandems and had a real mix but were all ocpd correctly but missed one that was on same leg in what was sposed to be mwbc,, but it was all lights and no recepts, Wasn't going to overload, not a serious error but when tested leg to leg net 0.

 

[wyliesdiesels]

In the areas where two sides of the 240 are not allowed in the same room it probably goes back to the early days of electric wiring. My dad wired houses starting from the knob and tube days. He was later a POCO supervisor and spent his entire working life in the field . He said that in the very early days they lost a housewife a year who was running a vac plugged into one circuit grabbing a lamp plugged into the other. In both cases the hot side of the circuit ended up in the lamp or vac frame way before grounded appliances. The unsuspecting housewife would get across 220 (now 240) volts and that was it. He had quite a few tales from the early days. He worked for a town generating plant on a small creek before the statewide POCO even existed.

That was also back when appliances grounded the frame through the neutral. The problem with this was that the neutral and hot blades on the plug were the same size so u could plug it in with the bonded neutral side plugged into the hot side of the outlet. If u touched the frame and another metal object that was plugged in ZAP 240v.

This is why plugs and outlets are now polarized. This prevents the neutral blade from being plugged into the hot side of the outlet.

Of course, nowadays neutrals on plugs are no longer allowed to be bonded to the frame. And either the appliance is 2-wire and double insulated or 3-wire/grounded...so polarization is not necessary anymore...

 

[rjkobbeman]

What I don't understand is why each hot wire is allowed to carry x amps of current, but the single neutral is allowed to carry 2x amps of current, the current carried simultaneously by both hot wires.

The neutral doesn't carry 2x the amps, it only carries the differential (difference) between the two circuits.

What makes this work is, THE TWO CIRCUITS MUST BE ON DIFFERENT LEGS WHICH MEANS THERE MUST BE 240 VOLTS ACROSS THE TWO CIRCUITS AND NOT 0 VOLTS. In this configuration the neutral only carries the difference. If one leg is pulling 15 amps and the other leg is pulling 13 amps, the neutral will see 2 amps. (The two circuits push/pull amps to/from each other.)

If the two circuits are on the same leg, then the neutral will carry the sum amps of the two circuits. This is dangerous and against code because the neutral will be undersized.

If wired correctly, it is completely legal and safe.

The downside to this "Edison circuit" (or multi-wire branch), is:
You are "sharing" the neutral which will trip GFCI and AFCI devices.
Does not save you very much money/labor vs running a second Romex.





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[wyliesdiesels]

The downside to this "Edison circuit" (or multi-wire branch), is: You are "sharing" the neutral which will trip GFCI and AFCI devices.
Does not save you very much money/labor vs running a second Romex.

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No need to run a second NM cable as Southwire now makes a Romex product that solves the shared neutral issue.

http://www.homedepot.com/p/Southwir...x-SIMpull-CU-NM-B-W-G-Wire-55048455/202316262

 

[Hot Rod Grampa]

It's your house and if you want 20 separate circuits in a one car garage and you do it safely and according to code then GO for it. Seldom do people complain about never ever tripping a breaker. Just do it right! And for that you got good advice. Never mind the noise.