# 3-Phase wiring



## Metersocket648 (Feb 8, 2021)

Why don't manufacturers produce 3-phase romex cable? And if the do make a 3-phase NM cable and I just didn't look thoroughly, would we still have to use the wiring methods in chapter 3 : Article 300.3(B) with the use of Emt conduit or it that code to use emt conduit with any 3-phase installation? 🤔 seeing a roll of 12/4, 10/4, 8/4 or even 6/4 in an electrical warehouse one day would definitely ease the process of installing 3-phase wiring instead of buying 5 different spools of THHN wire to pull through an emt conduit run.


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## just the cowboy (Sep 4, 2013)

Few things;
1. Romex is for houses not Industrial so it would sit on the shelf.
2. Romex is solid wire and does not do well heating and contracting in industrial.
3. Look up tray cable it may be what you need in some cases.

Cowboy


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## SWDweller (Dec 9, 2020)

They make MC cable for 3 phase, even with stranded wire. 
Wire and Cable your way even has conductors down to 14 awg

Notice no one ever said this stuff was going to be inexpensive.

I remember some new stadium was constructed and they used all MC cable. Saw it in ECM magazine.


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## Metersocket648 (Feb 8, 2021)

just the cowboy said:


> Few things;
> 1. Romex is for houses not Industrial so it would sit on the shelf.
> 2. Romex is solid wire and does not do well heating and contracting in industrial.
> 3. Look up tray cable it may be what you need in some cases.
> ...


I've done a couple of residential houses that had a 120/208 3-phase system, and getting the emt in there was a pain, the SE pull was ridiculously long, the meter base is on one side of the house and I had to run rigid emt from the back of the base, up the wall into the second floor, through the ceiling, down the other wall across the upstairs room, into the first floor ceiling, above the kitchen and finally into the panel in the garage on the other side of the kitchen wall. Surely they would allow use of NM romex in residential installations,


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## Metersocket648 (Feb 8, 2021)

SWDweller said:


> They make MC cable for 3 phase, even with stranded wire.
> Wire and Cable your way even has conductors down to 14 awg
> 
> Notice no one ever said this stuff was going to be inexpensive.
> ...


What would you use 14/4 for? What kind of 3-phase load would be useful on 15 amps? Lighting maybe? But most commercial lighting circuits are 277v


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## kb1jb1 (Nov 11, 2017)

As far as I know, you can use type NM cable in commercial applications under certain conditions. They make all kinds of configurations depending on what is common in your area. 12/4, 10/4, 8/4,... They even have NM with dedicated neutrals but it is easier to get MC. Don't forget about AFCI and GFCI if you are using it as multi wire circuits. Also common trip. Personally I have stopped using multi wire circuit 15 plus years ago.


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## Metersocket648 (Feb 8, 2021)

kb1jb1 said:


> As far as I know, you can use type NM cable in commercial applications under certain conditions. They make all kinds of configurations depending on what is common in your area. 12/4, 10/4, 8/4,... They even have NM with dedicated neutrals but it is easier to get MC. Don't forget about AFCI and GFCI if you are using it as multi wire circuits. Also common trip. Personally I have stopped using multi wire circuit 15 plus years ago.


Where would I be able to aquire this NM 3-phase cable? Southwire?


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## ohm it hertz (Dec 2, 2020)

14/4 mc was great for multi wire branch circuits from panel to jbox in office buildings for lighting. Just balance the panel and enjoy using less wire. We did it for general purpose circuits, too.

There's days I miss 3 phase.


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## emtnut (Mar 1, 2015)

Where did you get your rigid EMT ??


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## Metersocket648 (Feb 8, 2021)

ohm it hertz said:


> 14/4 mc was great for multi wire branch circuits from panel to jbox in office buildings for lighting. Just balance the panel and enjoy using less wire. We did it for general purpose circuits, too.
> 
> There's days I miss 3 phase.


What were the color coding for the 14/4 mc? Red, Black and Blue or did yall use yellow, orange and brown for it?


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## joe-nwt (Mar 28, 2019)

Although there are a few rare instances where some 4C NM might come in handy, can you imagine what the DIYers would do with it if it was commonly available?


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## Metersocket648 (Feb 8, 2021)

emtnut said:


> Where did you get your rigid EMT ??


Menards, The home depot, Lowes, sometimes even an electrical warehouse, i used a 2" diameter for the SE


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## ohm it hertz (Dec 2, 2020)

Metersocket648 said:


> What were the color coding for the 14/4 mc? Red, Black and Blue or did yall use yellow, orange and brown for it?


Black/red/blue.

I never worked with the other voltages.


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## Metersocket648 (Feb 8, 2021)

joe-nwt said:


> Although there are a few rare instances where some 4C NM might come in handy, can you imagine what the DIYers would do with it if it was commonly available?


Electrican: (looking at a single phase 120/240v panel) "what the hell is this?? Where does this 4 conductor cable go?"

DIYer Homeowner: (points at the installation confidently) "Yeah! I used this neat 4 conductor cable to save money on cable, it runs my bedrooms and kitchen outlet circuits, I didn't have to use two runs of cable. Pretty neat, Eh?

Electrican: You've soiled my very name🤢😖😣


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## kb1jb1 (Nov 11, 2017)

14/4 MC most common colors would be blue, black, red, white, green. MC can be ordered with different colors and configurations with many conductors. I believe AC cable can only be made with 4 conductors and limited colors.


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## kb1jb1 (Nov 11, 2017)

I am still trying to grasp what three phase NM cable is. 12/3 can be used as a three phase cable but not a three circuit cable. NM is usually called ; xx/2, xx/3, xx/4.


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## Forge Boyz (Nov 7, 2014)

Metersocket648 said:


> What would you use 14/4 for? What kind of 3-phase load would be useful on 15 amps? Lighting maybe? But most commercial lighting circuits are 277v


Romex is rated for 600v. So it could be used for that. I was in a farm shop that had 277v lighting circuits in it and they had run romex down the posts to the switch boxes. Gave me the willies. No way would I do that.

Sent from my SM-G970U using Tapatalk


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## dspiffy (Nov 25, 2013)

I've worked on several commercial properties that were three phase and almost entirely wired in romex. However the only circuits that were 3 phase were HVAC. Everything else was lighting, outlets, and 208v appliances.

I'm trying to remember how they fed the rooftop units.


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## micromind (Aug 11, 2007)

Tek cable is available with the low voltage 3Ø colors.


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## micromind (Aug 11, 2007)

dspiffy said:


> I've worked on several commercial properties that were three phase and almost entirely wired in romex. However the only circuits that were 3 phase were HVAC. Everything else was lighting, outlets, and 208v appliances.
> 
> I'm trying to remember how they fed the rooftop units.


I've seen this as well, usually a short piece of EMT is stubbed down through the roof and the NM is shoved into it.


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## LGLS (Nov 10, 2007)

emtnut said:


> Where did you get your rigid EMT ??


Username checks out, and asking the real questions.


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## LGLS (Nov 10, 2007)

Metersocket648 said:


> Why don't manufacturers produce 3-phase romex cable? And if the do make a 3-phase NM cable and I just didn't look thoroughly, would we still have to use the wiring methods in chapter 3 : Article 300.3(B) with the use of Emt conduit or it that code to use emt conduit with any 3-phase installation? 🤔 seeing a roll of 12/4, 10/4, 8/4 or even 6/4 in an electrical warehouse one day would definitely ease the process of installing 3-phase wiring instead of buying 5 different spools of THHN wire to pull through an emt conduit run.


Consider the miles and miles of NM cable produced and in the quantities and sizes most needed, and how just adding one conductor to a 12/2 adds to the price, the number of times a 3 phase NM cable could prove handy and who is going to cash in on that efficiency and how, and who would lose out on that rarity and why, and you come to understand why many products a few people might like a few times will never be mass manufactured. 
Like, people who want a 1 gang dimmer/fan speed control, but need the light dimmer to be 3-way. It's not happening.


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## kb1jb1 (Nov 11, 2017)

Please, what is a three phase cable??


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## paulengr (Oct 8, 2017)

kb1jb1 said:


> Please, what is a three phase cable??


Generally speaking typically a 4 conductor cable (3 wire plus ground or 3 wire plus neutral).

As far as I’m concerned MC is a waste of time for 3 phase. Type TC-ER is tested to the same crush/impact tests as type MC but you use CGBs for termination and there is no armor to contend with. Like MC as long as it is supported it can in or out of a tray without distance limits or even any tray at all. Effectively TC-ER is “NM for industrial”.


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## Metersocket648 (Feb 8, 2021)

Forge Boyz said:


> Romex is rated for 600v. So it could be used for that. I was in a farm shop that had 277v lighting circuits in it and they had run romex down the posts to the switch boxes. Gave me the willies. No way would I do that.
> 
> Sent from my SM-G970U using Tapatalk


They ran romex down the posts? Unprotected? Or in RMT/EMT? Wouldn't the romex be suspect to damage in this environment?


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## Metersocket648 (Feb 8, 2021)

kb1jb1 said:


> Please, what is a three phase cable??


Not so much as 3-phase cable but cable that has all 4 conductors plus a ground and is nm like romex.


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## kb1jb1 (Nov 11, 2017)

So it is 12/3 or 12/4 NM? Why call it three phase cable? Both are readily available. 
I worked in a commercial building that was wired in NM cable years ago and all the lighting was NM @277 volts. The home run circuits were 10/4. So is the home run considered three phase cable? I call it a multi wire branch circuit.


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## Metersocket648 (Feb 8, 2021)

kb1jb1 said:


> So it is 12/3 or 12/4 NM? Why call it three phase cable? Both are readily available.
> I worked in a commercial building that was wired in NM cable years ago and all the lighting was NM @277 volts. The home run circuits were 10/4. So is the home run considered three phase cable? I call it a multi wire branch circuit.


Yes that's what I mean by 3-phase cable


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## RAD COM (Mar 3, 2019)

Metersocket648 said:


> Where would I be able to aquire this NM 3-phase cable? Southwire?


Here is a screen shot of Southwire's Simpull cable. It say suitable for use in all applications as specified by the NEC.
I use the 12-2-2 for 3-way switching, switch leg runs, and branch circuit home runs. I've never seen the 12-4 stocked anywhere though.


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## Forge Boyz (Nov 7, 2014)

Metersocket648 said:


> They ran romex down the posts? Unprotected? Or in RMT/EMT? Wouldn't the romex be suspect to damage in this environment?


It's been a few years since I was there but I believe they just ran the wire down the posts. 

Sent from my SM-G970U using Tapatalk


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## Quickservice (Apr 23, 2020)

I'm going to start collecting some of these questions.... They are either too horrifying or too funny to let get away.


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## emtnut (Mar 1, 2015)

kb1jb1 said:


> Please, what is a three phase cable??


It's very special cable, specifically designed to allow for the phase differential encountered in many 3 phase systems.

Surprised you haven't heard about it ! 😂


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## emtnut (Mar 1, 2015)

Metersocket648 said:


> They ran romex down the posts? Unprotected? Or in RMT/EMT? Wouldn't the romex be suspect to damage in this environment?


It could certainly be damaged. The RMT would come in handy then


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## cuba_pete (Dec 8, 2011)

emtnut said:


> It's very special cable, specifically designed to allow for the phase differential encountered in many 3 phase systems.
> 
> Surprised you haven't heard about it ! 😂


It adjusts for lead and lag automatically? Cool!

No more balancing panels...comes with a free Stetzerizer* with every 1,000' purchased.

*Gift of Stetzerizer not valid with any other offer, discount, or coupons.


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## emtnut (Mar 1, 2015)

cuba_pete said:


> It adjusts for lead and lag automatically? Cool!
> 
> No more balancing panels...comes with a free Stetzerizer* with every 1,000' purchased.
> 
> *Gift of Stetzerizer not valid with any other offer, discount, or coupons.


I was getting excited .... until I read the fine print 😢


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## jarrydee (Aug 24, 2019)

They sell 12/4 and 14/4 romex


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## wcord (Jan 23, 2011)

I'm still wrapping my head around rigid emt.
How do you thread the stuff?


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## ohm it hertz (Dec 2, 2020)

wcord said:


> I'm still wrapping my head around rigid emt.
> How do you thread the stuff?


You don't. Just get a combo coupler to switch over to rigid non metallic liquidtight. Problem solved!

now where to find rigid liquidtight...


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## Metersocket648 (Feb 8, 2021)

wcord said:


> I'm still wrapping my head around rigid emt.
> How do you thread the stuff?


They do have a threading machine for rigid emt or for any rigid metallic pipe, harbor freight sells them for cheap but if you want a high quality electric pipe threader, your looking at spending at least 1,000$+ for one, especially the tripod mounted ones that you place on the ground, heres a link to a handheld pipe threader from harbor freight threading machine for rigid emt - Google Shopping


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## Quickservice (Apr 23, 2020)

This thread has become completely unhinged!!! 😱 🙄 😬


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## Quickservice (Apr 23, 2020)

emtnut said:


> It's very special cable, specifically designed to allow for the phase differential encountered in many 3 phase systems.
> 
> Surprised you haven't heard about it ! 😂


Uh.. is that the same as preventing an unbalanced load? 🤪


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## Metersocket648 (Feb 8, 2021)

Quickservice said:


> This thread has become completely unhinged!!! 😱 🙄 😬


I couldnt help but laugh at that 😂😂


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## kb1jb1 (Nov 11, 2017)

emtnut said:


> It's very special cable, specifically designed to allow for the phase differential encountered in many 3 phase systems.
> 
> Surprised you haven't heard about it ! 😂


I guess I have to re-learn vector calculus. That phase differential can wreak havoc if the metrics are not correct.


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## kb1jb1 (Nov 11, 2017)

ohm it hertz said:


> You don't. Just get a combo coupler to switch over to rigid non metallic liquidtight. Problem solved!
> 
> now where to find rigid liquidtight...


Don't forget to wrap everything with green electrical tape.


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## wcord (Jan 23, 2011)

Metersocket648 said:


> They do have a threading machine for rigid emt or for any rigid metallic pipe, harbor freight sells them for cheap but if you want a high quality electric pipe threader, your looking at spending at least 1,000$+ for one, especially the tripod mounted ones that you place on the ground, heres a link to a handheld pipe threader from harbor freight threading machine for rigid emt - Google Shopping


EMT wall is only .049 inches thick.
by the time you thread emt, there is no material left.
I believe you are referencing RGS or rigid conduit


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## Quickservice (Apr 23, 2020)

kb1jb1 said:


> Please, what is a three phase cable??


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## 99cents (Aug 20, 2012)

I do small three phase TI’s and never use cable with more than two conductors. The exception could be something like a three phase MUA and then I use Teck. 

I did a wood frame commercial building a year ago and that was Romex. We used ENT for conduit. The only metallic conduit was for fire alarm.


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## Max C. (Sep 29, 2016)

So how do you thread rigid PVC? Asking for a friend...


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## emtnut (Mar 1, 2015)

wcord said:


> I'm still wrapping my head around rigid emt.
> How do you thread the stuff?


I think your kidding, but you need to use an EMT-TA . Pretty much any epoxy will hold it.


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## Metersocket648 (Feb 8, 2021)

wcord said:


> EMT wall is only .049 inches thick.
> by the time you thread emt, there is no material left.
> I believe you are referencing RGS or rigid conduit


Yes thats what I meant


Max C. said:


> So how do you thread rigid PVC? Asking for a friend...


I've never seen Rigid PVC threaded


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## kb1jb1 (Nov 11, 2017)

Max C. said:


> So how do you thread rigid PVC? Asking for a friend...


You use the white PVC.

You buy it in the plumbing section of Home Depot.


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## ohm it hertz (Dec 2, 2020)

Paint it gray, the inspector won't notice.


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## gpop (May 14, 2018)

Max C. said:


> So how do you thread rigid PVC? Asking for a friend...


Pony motor. A friend told me when he ran out of pvc adapters while changing from ridgid to pvc underground.


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## SteveBayshore (Apr 7, 2013)

Metersocket648 said:


> Yes thats what I meant
> I've never seen Rigid PVC threaded


Schedule 80 PVC threaded nipple. We thread schedule 80 PVC in a threading machine with standard dies. Pipe has to be warm to start and use slow speed, pretty tedious.







This one was cut with a nipple chuck.


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