Installing 120v outlets with upgradeability to 240v

[utbigrod]

Hi all, I'm adding in some new circuits to a 100A subpanel. I've decided to surface mount the outlets vs. doing EMT just to make it look nice. Since I'm not doing EMT I want to make the install as flexible as possible.

I don't have the immediate need, but could have future need for 240v on some of these outlets. E.g. I upgrade my bandsaw to a 240v model from a 120v model. If I run 12/3 from the subpanel then it seems like I'd have future upgradeability whereas in the current situation I would just use the black hot and white neutral (along with ground of course) to connect the 120v outlets (2 in a quad box) to a 20A 120v breaker and leave the red wire disconnected at both ends, probably with a wire nut on both ends for good measure.

Then if I wanted to switch to 240v I could run the black hot and red hot (along with ground) to the 240v outlet and to a 2-pole 240v 20A breaker.

So is that doable? And do I really need 12/3 or could I use 12/2 and use the white for hot if I ran 240V?

thanks!
Brad

 

[rockwithjason]

i can't recall off of the top of my head if there is a code section that specifically allows you to relable the neutral as a hot by taping or other means, my instinct says no. with that said, in the everyday world it's done all the time and will work. it' helps to label the neutrals for ease. if it were me i would run the 12/3 and spare off the red.

 

[teamextreme]

You can run either 12/2 or 12/3. 12/3 would be used as you describe. 12/2 can also be used but you have to remember a couple of things. One, make sure you leave enough length on the white wire in the panel to reach a breaker. Often times the neutral ends up being cut somewhat short when it ties to the neutral bus and it can't reach a breaker if it's re-purposed for that. Second and most importantly, to do this you have to run dedicated circuits to each outlet you are considering setting up like this. You can't daisy chain 120v outlets, then try to convert one of them to 240 down the road. Third, the white wire has to be re-identified by taping it black. No code violations in doing this.

 

[7thDimension]

Couldn't you just wire it like a mwbc, so that you have two outlets on two different circuits in each box, and double pole breakers in the panel?

So then, if you wanted 240, you'd only have to replace the outlet and nothing else...

 

[sberry]

This is planning way too far ahead for something you will likely never use. This would assume the appliance would run on 12 wire. Small items would but leaving some method to get back to the panel would be ok in case it ever happened.

 

[Scsmith42]

I wired my shop in a manner that allows me to have 120 or 240 available at most receptacles. Everything is done with a conduit infrastructure that allows me to pull additional wiring in the future.

It is best to use stranded wire as opposed to solid (and do not use to romex in conduit), stranded pulls much more easily through the bends.

What I did was to install double gang boxes everywhere with a pair of standard 120v receptacles in them. Each receptacle is wired to separate breaker with the breakers being adjacent to one another in the panel (but on separate legs of the feed). If I want 240 at ant location all that I have to do is swap the receptacle and breakers for the proper 240 one.

Makes it easy to upgrade albeit it at a cost of additional breakers, wire and larger load center up front. Each receptacle box has two hots from different legs of the power, two neutrals ( but I probably could have shared one since the receptacles are on two different legs), and a shared ground.


Scott

 

[pattenp]

You get into code issues with using a MWBC when trying to power 240V and 120V. You need to read NEC 210.4. Typically MWBC are for Line-to-Neutral loads. There are exceptions for Line-to-Line loads on a MWBC.

 

[Wirepuller]

i can't recall off of the top of my head if there is a code section that specifically allows you to relable the neutral as a hot by taping or other means, my instinct says no. with that said, in the everyday world it's done all the time and will work. it' helps to label the neutrals for ease. if it were me i would run the 12/3 and spare off the red.

You can use white as an ungrounded conductor as long as its in a pre manufactured cable.

 

[Fishplate]

What I did was to install double gang boxes everywhere with a pair of standard 120v receptacles in them. Each receptacle is wired to separate breaker with the breakers being adjacent to one another in the panel (but on separate legs of the feed).

Do you have the breaker handles tied together?

 

[Scsmith42]

Do you have the breaker handles tied together?

Not on the 120v circuits. When I convert a pair of receptacles to a 240 receptacle I also swap out the breakers for the correct 240 tandem breaker.


Scott

 

[sberry]

I found myself working on a circuit I thought was off the other day. Was my own fault and should have retested it. I do understand the fascination and there is a time and place for mwbc and it should be 2 pole but where do the 2 circuits a guy would want to convert come from?
I suppose you could convert one but I have never ever had to do this for myself or anyone else. I have turned 2 circuits in to 3 by adding a wire and making a mwbc but it was pretty rare.

 

[404]

Yes the white can be used as hot, in the old days? a piece of black tape was put on both ends to alert a later user. The 12/3 will allow all sorts of neat choices later with both 120 and 240 at the same time (code purists notwithstanding ). And the labor is about the same either way.

 

[sberry]

I own a dryer and an oven that are 3 pole 4 wire and a walk in cooler that most people do not have but nothing in my shop is multi voltage. About the only thing a guy might want is for a small welder but most of the time we would want a bigger wire so its new circuit time anyway.

 

[600SL]

My approach to this is shown here. I used conduit and ran 2 240V 3 wire lines and 2 120V lines + 1 dedicated 120V line. I kept the 240V lines in the upper conduit and the 120V lines in the lower conduit. It works very well. From any box I can pull either 120 or 240 volts or both or two 120 or 240V independent circuits if need be.

I used 3 wire so that my machines can get both power and lighting or other 120v accessories.

http://www.garagejournal.com/forum/showthread.php?t=262954

http://www.garagejournal.com/forum/showthread.php?t=269130

 

[RickP]

I don't have the immediate need, but could have future need for 240v on some of these outlets. E.g. I upgrade my bandsaw to a 240v model from a 120v model. If I run 12/3 from the subpanel then it seems like I'd have future upgradeability whereas in the current situation I would just use the black hot and white neutral (along with ground of course) to connect the 120v outlets (2 in a quad box) to a 20A 120v breaker and leave the red wire disconnected at both ends, probably with a wire nut on both ends for good measure.

Then if I wanted to switch to 240v I could run the black hot and red hot (along with ground) to the 240v outlet and to a 2-pole 240v 20A breaker.

So is that doable? And do I really need 12/3 or could I use 12/2 and use the white for hot if I ran 240?

Most of the 240v tools in the garage only need 2 conductors and a ground, so the third conductor wouldn't be needed even after you converted the circuit to 240v. Some exceptions would be ovens and maybe some heaters (with 120v blowers).

If you do decide to run MWBC's now, you should probably keep both circuits in the same 4x4 box, so you won't have issues with different voltages in different boxes later.

 

[600SL]

Most of the 240v tools in the garage only need 2 conductors and a ground, so the third conductor wouldn't be needed even after you converted the circuit to 240v. Some exceptions would be ovens and maybe some heaters (with 120v blowers).

If you do decide to run MWBC's now, you should probably keep both circuits in the same 4x4 box, so you won't have issues with different voltages in different boxes later.

3 wire comes in handy for me so I can put a 120V outlet right on my lift. Or put lights on my machines.

 

[RickP]

3 wire comes in handy for me so I can put a 120V outlet right on my lift. Or put lights on my machines.

Are you using a MWBC on a 120v machine? Or do you mean installing a 120v outlet on one leg of a 240v breaker? Just be careful with that - it's really easy to end up with inadequate breaker protection for the 120v wires. (I'm not even sure it's allowed by code, but one of the electricians might be able to help you with that question.)

An example of a code violation would be adding a 120v light on 12 ga wire to one leg of a 240v compressor circuit protected by a 50A breaker.

 

[sberry]

I saw this in a farm mag where a guy brought the bright idea to rig an outlet for 120 on the welder cord. Its been done without incident a lot but it doesn't make it a good idea, I am not sure what the statistical risk is and some of it would be dependent on hrs of use and condition but the editor said they got a couple calls about it.

 

[alfredeneuman]

The white wire in a cable is allowed to be marked on the ends with a permanent means (a felt tipped marker or heat shrink is the first things that come to mind), and used for a hot wire.

The same doesn't hold true for conduit.

 

[600SL]

Are you using a MWBC on a 120v machine? Or do you mean installing a 120v outlet on one leg of a 240v breaker? Just be careful with that - it's really easy to end up with inadequate breaker protection for the 120v wires. (I'm not even sure it's allowed by code, but one of the electricians might be able to help you with that question.)

An example of a code violation would be adding a 120v light on 12 ga wire to one leg of a 240v compressor circuit protected by a 50A breaker.

No this would be tapping the leg of a 240V circuit within the machine itself. My outlets are all 20Amp/2HP.

 

[sberry]

No this would be tapping the leg of a 240V circuit within the machine itself. My outlets are all 20Amp/2HP

I am interested in this.

 

[Radix2]

You get into code issues with using a MWBC when trying to power 240V and 120V. You need to read NEC 210.4. Typically MWBC are for Line-to-Neutral loads. There are exceptions for Line-to-Line loads on a MWBC.

I'm resurrecting this oldy to clarify that it is OK to use a mix of 120 and 240 outlets on a 20A MWBC per the NEC as long as exception 2 is followed and a double pole breaker is used (seems like that is a requirement anyway...)

this gives a picture of combined 120 and 240 outlets - http://mjobee.com/projects&news/nec art 210.4.pdf

setting up a woods shop with quite a few 240v machines, it would be handy to be able to have the flexibility to combine the runs. Anything missing?

 

[ishiboo]

I'm resurrecting this oldy to clarify that it is OK to use a mix of 120 and 240 outlets on a 20A MWBC per the NEC as long as exception 2 is followed and a double pole breaker is used (seems like that is a requirement anyway...)

this gives a picture of combined 120 and 240 outlets - http://mjobee.com/projects&news/nec art 210.4.pdf

setting up a woods shop with quite a few 240v machines, it would be handy to be able to have the flexibility to combine the runs. Anything missing?

NEC stupidity. I love how they explain this.

Multiwire branch circuits shall supply only line-to-neutral loads

Okay, so no 240v.

Exception No. 2: Where all ungrounded conductors of the multiwire branch circuit are opened simultaneously by the branch circuit over current device

Okay, 240v is now allowed since we just made an exception for EVERY SINGLE MWBC since that's a requirement of every MWBC?

 

[ForceFed70]

Darn, I'm late getting to this.

As has been identified, it is allowable to have a MWBC that contains a mix of 120V and 240V receptacles. I took advantage of that when I wired my garage.

This is how I wired my garage plugs:
- 20A 12-3 Romex 240V
- 2 gang boxes for all outlets
- left side of box has 20A 120V outlets wired as split receptacle - bottom and top on different 20A conductors for a total of 40A at 120V available.
- right side of box has 20A 240V outlets for a total of 20A at 240V

I ran two circuits like this to feed all of my general purpose outlets in the shop and it's worked amazingly well. Lots of 120V power and the 240V plugs work perfectly for my plasma cutter and welder (both smaller 240V units). The actual welder plugs haven't been used.

 

[rlitman]

...Okay, 240v is now allowed since we just made an exception for EVERY SINGLE MWBC since that's a requirement of every MWBC?

Well, we know that a common trip is a current requirement of an MWBC. But was it always? I don't think so. So, if you have an older MWBC, grandfathered without a common trip, 240V connections would not be ok.

 

[matt_i]

Just fish the red wire when its time to upgrade. Very easy & fast to do once the EMT is already mounted and ready. In my opinion, the bigger problem is to make sure to leave extra spaces in the panel so the double pole breaker can be landed in basically the same location as the original single pole without having to go to a new location where the black wire could be too short.

Note when planning the circuit, must have "homeruns" to the machine and not branched multi-device circuits unless the entire thing branches and all is going to 240vac.

 

[sberry]

If you are going to convert a circuit it cones at the expense of another. While all this is a warm thought and there is a place for it in residential garages where distance is short its so easy to wire a circuit to a box, leave some way back to the panel so when you get a new piece you can add service to it.
I have a lot of stuff. I have never upgrades something that really didn't require a new dedicated circuit. Have never done this, have seen a pile of wire parked for it and cant think of a single time where it has worked out, I am sure some where at some time it has, never had a call to convert one.
I do use some in my own, added some a while back to a job and was real tempting to add in everything I know and in the end just as easy to run 2 home and use 5 extra ft of wire but leave it simple, breaker to wire to outlet, not even a wire nut in it.
Not that it cant be done but as I related in other threads I got a call on a church with a long history, original by master, several handy man, a master during a reno who is a fuggin genius but he doesn't look for extra work.
It was super congested, new/ old. some Jbox, some work done in fixture boxes with multi wire etc.
The handymen that look at this figure its all fugged up but I said not so fast and I know the last guy and he aint gonna leave it with the wrong ocpd despite the wire sizes, had 1 30 on a 12, bunch of 15 on 12, 3 or 4 spare breakers he must have left when he added some tandems.
The whole thing was fine and dandy as he left it and maybe even for the next electrician provided the guy really was in some respect but a clusterfuk for anyone not intimately familiar with dozens of code sections.
They got a pocket full anyway and they didn't need it for demand reasons and it had an outside disconnect would have sold them an upgrade to a larger space panel and put it all one wire to a breaker vs leaving it a congested pit Edison would have trouble sorting out.
I do this all the time and was feeling chipper when I looked at it but if you were a bit less confident all the mwbc stuffed in there would have depressed a guy or as the handyman was considering changing breakers during some trouble shooting (which wasn't the issue) but certainly distracted from it.

 

[sberry]

There was an additional install for some AC done, one of the members has a SIL who is a master, talked with him and we agree how we gonna do this and get to straighten the mess for free, well he doesn't do exactly what was on the plan and says he gonna do.
They want me to do the committee so I will let it go, one day will take 2 men so we can do it all in after noon and move some stuff where it should be.
I hadn't been using camera phone and still don't think about it, should have snapped a panel pic.

 

[sberry]

Due to gfci and general confusion while I do have some wires pass thru some boxes I don't install but 1 circuit to it unless there is a compelling reason to do so and its not "just in case" for something highly unlikely to be needed. Its so much easier to cross when coming to it, it can be done, sounds great in theory but is about useless most of the time.
Only a couple places for light welding circuits and hoist feed does the wire all share he same pipe for a ways. In pipe I 3will run another piece or 2 back for dedicated circuits and I want to stay in small pipe, don't want to go to inch and larger Jboxes, all that stuff is great for industrial but a pain in the **** for residential and home garages. Got to stock 3 sizes and fittings for each.
I have one circuit I could convert to multi for the price of adding a wire down a pipe already in place. Once in 20 years it would have saved an extension cord for a coffee pot for a 4 hr party. It would cost a couple hours, 50 bucks in materials to improve something I wont use anyway.

 

[sberry]

The circuit breaker problem in another thread here says it all. http://www.garagejournal.com/forum/showthread.php?t=346077

 

[vtsoundman]

Well, we know that a common trip is a current requirement of an MWBC. But was it always? I don't think so. So, if you have an older MWBC, grandfathered without a common trip, 240V connections would not be ok.

No it was not always req'd...don't know when specifically it came into play...but it was fairly recent. Lots of 'newer' homes with solar being installed lack handle ties on MWBC.

 

[sberry]

Ok, had to read location, Are all 211 DVI with the factory adapter? There is no reason not to use 240 if its there, running thru another conversion process usually doesn't help anything.

 

[alfredeneuman]

Well, we know that a common trip is a current requirement of an MWBC.

It really isn't a current requirement. Common trip means that all poles will trip on an overload or short. The requirement is that you're capable of disconnecting the power with 1 flip of a circuit breaker handle. Only if it will be used for 240V duty is it required

(2014) NEC 240.15 (B) (1) Multiwire Branch Circuits. Individual single-pole circuit breakers, with identified handle ties, shall be permitted as the protection for each ungrounded conductor of multiwire branch circuits that serve only single-phase line-toneutral loads.