Wiring 110 and 220 in same box

[Brian D Smith]

any of you guys do this. I'm going to add a few 220v outlets on 3 different circuits in the coming weeks and this is my plan.

- get the single to double gang extension rings so I can surface mount the new boxes. run all my 220v through conduit and then install the 110v and 220v outlets in the same box. I'll be adding a few more 110v outlets as well so I'll but pulling 110 and 220 from the breaker panel (separate pulls, same conduit) as well.

basic idea is to have (for example) 220v outlet on the left of box and 110v outlet on the right of the box.

anyone else do this?

thanks,

Brian

[Matt Marsh]

Or you can go with a combo duplex receptacle such as the Leviton 5842.

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[Mike Henderson]

This idea was discussed in detail in a previous thread. Do some searching and you should find it.

Mike

[Todd Burch]

I haven't done it, but I have designed some layouts doing that. You can run a single 12/3 with ground to accomplish what you want. Black and Red are hot, white is common and bare is ground. (I typically use 10 awg for my 220 circuits though, and a deep box, or a quad box with a single round receptacle for 220.

Matt, I wasn't aware you could get a combo 5-20R / 6-20R in that config. Cool.

[Art Mann]

Just one word of caution. There are limits to how many and what gauge wire you pull through a specific size of conduit. It doesn't have anything to do with how many will physically fit. It has to do with heat dissipation. A fairly recent edition of the National Electrical Code (online for free) will tell you what is safe.

[Kent A Bathurst]

Or you can go with a combo duplex receptacle such as the Leviton 5842.

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I have 3 - 4 of these installed.

[Brian D Smith]

Thanks guys.

Yes I'm going to run 3/4" conduit so I'll be fine. Wasn't aware of the combo duplex either.

Also I did search, didn't see anything....thing about the search tool is it is highly dependent on the words you use.

Thanks again everyone.

Brian

[Brian D Smith]

one other question for those running the dual voltage outlets...are you using them in an unfinished space (like a garage) i'm required to have gfci in my shop because it's a garage. searching now to see if they have gfci versions.

[roger wiegand]

Keep in mind you can't run NM cable in conduit except over short distances for physical protection, its not rated for that. So you shouldn't use 12/3 cable, instead you should pull individual conductors in conduit.

To my knowledge, GFCI is not required for 240V outlets.

[Chris Padilla]

Or you can go with a combo duplex receptacle such as the Leviton 5842.

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I think that pic is upside down. ;)

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[Brian D Smith]

Roger,

I don't think 220v needs gfci either but my 110v does. How would I handle that if i were to use these?

Separate circuit for top and bottom I guess?

Also I'm aware of the limitations for running wire in conduit (at least this one haha) and planed to run individual wires not the 3 wire pre wrapped stuff.

[Mike Henderson]

Roger,

I don't think 220v needs gfci either but my 110v does. How would I handle that if i were to use these?

Separate circuit for top and bottom I guess?

Also I'm aware of the limitations for running wire in conduit (at least this one haha) and planed to run individual wires not the 3 wire pre wrapped stuff.
You'd pretty much have to pull separate 120V and 240V circuits to get the GFCI on the 120V circuits.

But additionally, you probably should think about how you want to wire your 240V circuits. Many tools that require 240V will pull 12 -15 amps. Unless you use very large wire, you'd probably need to have separate wire runs to the different 240V outlets if you ever plan to run more than one tool at a time.

I use a separate circuit for each 240V outlet in my shop for that reason. Almost all of my 240V circuits are wired with 12 gauge wire and use 20 amp breakers. I have one 30 amp circuit wired with 10 gauge wire.

The 120V outlets are wired with 12 gauge, and 20 amp breakers, and there are multiple outlets on each circuit. At the head of each 120V multidrop circuit I have a GFCI that serves all the outlets downstream on that circuit.

Mike

[Matt Marsh]

You could separate the circuits, or you could feed everything with a 2-pole 120/240 volt GFCI breaker.

[Brian D Smith]

You'd pretty much have to pull separate 120V and 240V circuits to get the GFCI on the 120V circuits.

But additionally, you probably should think about how you want to wire your 240V circuits. Many tools that require 240V will pull 12 -15 amps. Unless you use very large wire, you'd probably need to have separate wire runs to the different 240V outlets if you ever plan to run more than one tool at a time.

I use a separate circuit for each 240V outlet in my shop for that reason. Almost all of my 240V circuits are wired with 12 gauge wire and use 20 amp breakers. I have one 30 amp circuit wired with 10 gauge wire.

The 120V outlets are wired with 12 gauge, and 20 amp breakers, and there are multiple outlets on each circuit. At the head of each 120V multidrop circuit I have a GFCI that serves all the outlets downstream on that circuit.

Mike

thanks Mike that is what I figured, separate runs for both. I will only have to pull 120v from the panel for one outlet as I want to add one more standalone circuit. other then that I have quite a few 120v circuit already in place (wiring in walls) so I will just be pulling the 220v wiring to those areas via conduit.

I plan to install 20 amp 220v circuits for my tools...all on one circuit as this is my own personal shop and I will not be running more then 1 tool at a time because I'm the only one working in it.

separately though I'm planning a dedicated 220v circuit for my DC as well as another dedicated circuit run to the ceiling (haven't decided location yet) for a heater in the future. I also have a 110v 15 amp circuit for the garage door and ceiling lights, and I'll be adding another 110v 15amp in the ceiling near the center of the space for my air filtration.

I was just focusing on the "tool" outlets/circuits here because those are the ones that will be sharing physical space.

I have GFCI outlets in place at the start of each 120V circuit already (I have 3 dedicated circuits for 6 outlet locations), so I should be good there :)

sounds like I can use those dual voltage outlets and have 1x220v and 3x110v outlet at each location all in a 4 square surface mount box??

that would be fantastic!!

[Kent A Bathurst]

You could separate the circuits, or you could feed everything with a 2-pole 120/240 volt GFCI breaker.

THis is what I would look into..........

[Kent A Bathurst]

I think that pic is upside down. ;)

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But, CHris - you forgot the long-ish thread on mounting recepts ground-up v. ground down. THe common wisdom was ground up.

[Julie Moriarty]

Since you're using conduit, you'll have to identify the neutrals with the hots they serve, at both ends of the conduit runs. For a 240V single phase service, (2) hots and (1) neutral make up a network. (For three phase, it's (3) hots for each neutral.) Code allows for (9) current carrying conductors through any wiring chase cross section. That means a maximum (9) hot wires can be pulled in a conduit. It doesn't make any difference if it's 3/4" or 4" conduit. That's as of the 2008 code, the one in effect when I retired.

When pulling the wires, strip the ends of the wires (leaving one stripped a few inched longer than the others) then twist the hots with their respective neutrals and the long one becomes the tail you'll thread through the fish tape end. Make sure you mark the reels too. The networks should be taped together just in case you cut the tails off after pulling. When you get to the other end you'll know what neutral goes to which hots.

On the panel end, before you cut the wires for trimming, tape the networks together where they exit the conduit. Then you will always be able to identify the networks after they are trimmed into the breakers. When working on panels that have neutral busses running down each side of the panel, adjacent to the breakers, I like to trim the neutrals between the two breakers feeding the hots. At junction boxes with more than one network in it, I tape the networks together there too.

Colored tape or wire markers can help you identify the networks when two or more are in a single pull. Identifying the wires before you pull them in will make for an easy termination.

[Todd Burch]

Roger, you are correct. I forgot the "surface mount" parameter.



... Code allows for (9) current carrying conductors through any wiring chase cross section. That means a maximum (9) hot wires can be pulled in a conduit. ...

I thought I read in an NEC commentary some place that grounds were to be treated as current carrying, since in a failure, they could carry current.

[Brian D Smith]

I would have to look but I don't think grounds count.

Julie,

Awesome advice and thanks for telling me about 9 wires. I was referencing 3/4" because I believe 1/2" will be too small and not be against code.

I'm going surface mount because half the garage has living above it and I hate patching drywall. So doing it all surface is smart for me.

Brian

[Art Mann]

Here is a chart I found on the internet describing how many and what type conductors can populate a given piece of conduit. It was easier to find than searching through the NEC. You certainly won't have any problem with 3/4" conduit of any type.

http://www.allenelectric.com/referencedata/conduitfill.htm

[Steve Meliza]

My goole-foo may not be up to the task, but the only 2-pole 120/240 volt GFCI breaker that I could readily find was a Siemens 15A breaker. That seems like a rather large limitation and the cost ($62) would pay for a lot of wire that could be used to run separate 120 and 240 circuits.

[Julie Moriarty]

I thought I read in an NEC commentary some place that grounds were to be treated as current carrying, since in a failure, they could carry current.
That 9 current carrying conductor rule was a thorn in our collective sides, depending on the inspector. So it was discussed a lot on the job. I do recall someone talking about ground wires qualifying and that, of course, started discussions about neutrals carrying current. At the time, one of our code gurus recited something from the NEC that eliminated ground and neutral wires. I think I remember reading something backing that up. I never ran across one inspector who counted anything but hots when inspecting the jobs. The discussions about grounds being current carrying eventually died.


I was referencing 3/4" because I believe 1/2" will be too small and not be against code.

I'm going surface mount because half the garage has living above it and I hate patching drywall. So doing it all surface is smart for me.

Brian

It's crazy what they allow for conduit fill. I remember when they changed the code and what I heard mostly was, "Now you can pull it as many wires as will fit." But the (9) hots usually keeps the fill under code. When pulling all #12, it made no sense going larger than 3/4" conduit because of that rule.

If you run conduit from the panel to the load, you probably won't be pulling any ground wires. Everything around here is conduit and it's almost always the only ground unless there are isolated grounds. Just make sure fittings and all connections are tight.

When you're running the conduit between boxes, you can save yourself some bending at the boxes if you use minis http://www.wescodirect.com/direct/images/products/small/minerac00001_28_tr_001.jpg as conduit hangers. If you use one or two hole straps http://www.wescodirect.com/direct/images/products/small/minerac00002_20_tn_001.jpg you'll have to bend a box offset at every box. But if you have an offset bender http://ecx.images-amazon.com/images/I/31k5abbwu3L._SL500_SS120_.jpg the job goes faster. :D I'm also partial to EZ anchors over pretty much anything else when anchoring into drywall. If installed correctly, they hold very well.

[Matt Marsh]

My goole-foo may not be up to the task, but the only 2-pole 120/240 volt GFCI breaker that I could readily find was a Siemens 15A breaker. That seems like a rather large limitation and the cost ($62) would pay for a lot of wire that could be used to run separate 120 and 240 circuits.

I believe all of the current manufacturers make a 2-pole 240/120 volt GFCI breaker. The comparative ease of installation and less materials needed for it would usually offset the cost of the GFCI breaker. Instead of two 12/2 cables in and two 12/2 cables out of every box, you could get by a single 12/3 in and a single 12/3 out. The separate circuit way would have a minimum wire count of 11 wires, compared to 9 with the 3-wire. With #12s that would require a minimum size box of 24.75 cu. inches, versus 20.25 for the 3-wire. Plus you would have the added safety of your 240 volt loads having GFCI protection.

[Matt Marsh]

Code allows for (9) current carrying conductors through any wiring chase cross section. That means a maximum (9) hot wires can be pulled in a conduit. It doesn't make any difference if it's 3/4" or 4" conduit. That's as of the 2008 code, the one in effect when I retired.

Julie, you're not saying this is true in all cases are you? Is there an obscure interpretation somewhere I have never heard about? The code certainly allows for more than 9 current carrying conductors in a single raceway, it's just that with 10 to 20 current carrying conductors, you must derate their ampacities to 50% (as per table 310.15(B)(3)(a), which for example effectively brings the ampacity of a #12 90°C rated copper conductor down to the point it can no longer be protected by a 20 amp overcurrent device. But you could indeed compensate by installing larger conductors.

[Steve Rozmiarek]

That 9 current carrying conductor rule was a thorn in our collective sides, depending on the inspector. So it was discussed a lot on the job. I do recall someone talking about ground wires qualifying and that, of course, started discussions about neutrals carrying current. At the time, one of our code gurus recited something from the NEC that eliminated ground and neutral wires. I think I remember reading something backing that up. I never ran across one inspector who counted anything but hots when inspecting the jobs. The discussions about grounds being current carrying eventually died.



It's crazy what they allow for conduit fill. I remember when they changed the code and what I heard mostly was, "Now you can pull it as many wires as will fit." But the (9) hots usually keeps the fill under code. When pulling all #12, it made no sense going larger than 3/4" conduit because of that rule.

If you run conduit from the panel to the load, you probably won't be pulling any ground wires. Everything around here is conduit and it's almost always the only ground unless there are isolated grounds. Just make sure fittings and all connections are tight.

When you're running the conduit between boxes, you can save yourself some bending at the boxes if you use minis http://www.wescodirect.com/direct/images/products/small/minerac00001_28_tr_001.jpg as conduit hangers. If you use one or two hole straps http://www.wescodirect.com/direct/images/products/small/minerac00002_20_tn_001.jpg you'll have to bend a box offset at every box. But if you have an offset bender http://ecx.images-amazon.com/images/I/31k5abbwu3L._SL500_SS120_.jpg the job goes faster. :D I'm also partial to EZ anchors over pretty much anything else when anchoring into drywall. If installed correctly, they hold very well.

Good stuff Julie. I'm installing conduit in my new shop over concrete walls. I want the minimum amount of attachments to the concrete, how often do I have to put a hanger?

[Art Mann]

I used PVC conduit in my shop so separate ground wires had to be pulled. I used 3/4" conduit because it is so much easier to get several wires through a long and twisting path. The price difference is small so why not?

[Julie Moriarty]

Julie, you're not saying this is true in all cases are you? Is there an obscure interpretation somewhere I have never heard about? The code certainly allows for more than 9 current carrying conductors in a single raceway, it's just that with 10 to 20 current carrying conductors, you must derate their ampacities to 50% (as per table 310.15(B)(3)(a), which for example effectively brings the ampacity of a #12 90°C rated copper conductor down to the point it can no longer be protected by a 20 amp overcurrent device. But you could indeed compensate by installing larger conductors.

Matt, you are right. If you follow the derating parameters, there's no need to use the 9 max "rule". But how many of us ever derate wires when we do the calcs on our workshops? I know I don't. And it can actually become more costly if you insist on loading up the conduits with the maximum wires. I worked for one of the largest ECs in Illinois and they had a standard where if the max size conductor was #12, the max conduit was 3/4". And I did "time" as an estimator and there was no way around the code where installing more than 9 CCC max was profitable.

[Julie Moriarty]

Good stuff Julie. I'm installing conduit in my new shop over concrete walls. I want the minimum amount of attachments to the concrete, how often do I have to put a hanger?

Unless the code has changed, hangers are required not more than 30" from every fitting. That means every coupling, connector, unilet or whatever else you use to join everything together. I install hangers 30" from a box and no more than 60" in between. It makes for a very solid installation. If your conduit will be exposed, you may want to follow that even if it means drilling a few extra holes. Workshop walls can take a beating and it's a pain to have to fix something you already installed, especially electrical stuff. If you're mounting the conduit flush to the walls (box offsets and all) it's not that critical but if you're using minis you'll want an installation a bit beefier.

[Steve Rozmiarek]

Thanks Julie. As I don't have a cool offset bender, and those minis look easier than trying to execute an offset with my old fashioned ridgid bender, I guess I'll get comfortable drilling anchors.

[Keith Weber]

Julie, you're not saying this is true in all cases are you? Is there an obscure interpretation somewhere I have never heard about? The code certainly allows for more than 9 current carrying conductors in a single raceway, it's just that with 10 to 20 current carrying conductors, you must derate their ampacities to 50% (as per table 310.15(B)(3)(a), which for example effectively brings the ampacity of a #12 90°C rated copper conductor down to the point it can no longer be protected by a 20 amp overcurrent device. But you could indeed compensate by installing larger conductors.

Julie,

I was going to challenge you on your limit of 9 current carrying conductor statement, because it's not actually true, but Matt beat me to the punch and said basically what I was going to say. Conduit fill is, in fact, dependent on the size of the conduit. That's the whole purpose of a conduit fill chart. As Matt suggested, you have to consider derating the ampacities. I for one did in fact consider this in my workshop -- as well as considering voltage drop on longer runs. If the derate became an issue (not often), it was just a matter of upping the wire size. Yeah, it costs a little more, but so does having a fire and finding out your insurance won't cover it because your wiring was not to code.

[Julie Moriarty]

Thanks Julie. As I don't have a cool offset bender, and those minis look easier than trying to execute an offset with my old fashioned ridgid bender, I guess I'll get comfortable drilling anchors.
Box offsets aren't hard to make unless perfect uniformity is required. I flip the bender over and make a quick bend right at the end of the conduit, then flip it 180 and do the same. With practice you can make them all pretty much identical.


Julie,

I was going to challenge you on your limit of 9 current carrying conductor statement, because it's not actually true, but Matt beat me to the punch and said basically what I was going to say. Conduit fill is, in fact, dependent on the size of the conduit. That's the whole purpose of a conduit fill chart. As Matt suggested, you have to consider derating the ampacities. I for one did in fact consider this in my workshop -- as well as considering voltage drop on longer runs. If the derate became an issue (not often), it was just a matter of upping the wire size. Yeah, it costs a little more, but so does having a fire and finding out your insurance won't cover it because your wiring was not to code.

On the whole, derating costs more than installing another conduit. The setup takes more time, wire pulls get harder and trimming out devices can become more difficult. You don't want to have to bring in a tugger to make the wire pull on #12 wires. Poor conduit layout can bring a job to a halt.

I'm no fan of the NEC wire fill max. I've never worked with any electrician who is. We have to pull those wires and know how hard it can be. It just isn't worth it. So most contractors around here, where everything is in conduit, stick with 9 CCCs as the max in any conduit but it's not that often utilized. Many contractors stop at two networks for wire fill. It allows for future additions and is easier to pull on the original.

When I piped my house, I upped the conduit size for home runs and longer pulls with more than 270 degrees of bends in them. It cost a bit more in conduit but it sure made the wire pull easier. When laying out a job I make the conduit install the hardest part of the job so everything after that is progressively easier. My jobs almost always made money. If you don't layout the conduit install right the first time, it can cost you a bundle down the road. The NEC is great as a guideline but following it to its limits can make your life hell. Knowledge of the NEC is only a small part of designing a good electrical installation.

Next time, I'll just say, "My experience tells me this is the way to do it. Take that with as many grains of salt as you wish." ;)

[Chris Padilla]

Thanks for the explanations, Julie. I see the 9 CCC limit is more of a practical limit based on real world experience dictated mostly by economics. Cool stuff!

[Steve Rozmiarek]

Thanks Julie, it's good to hear real word experience. It sure helps my project go smoother, and that's what counts to me. If I can shave a day on installation, i'm woodworking a day sooner.

[Brian D Smith]

Thank you for all the info Julie et al.