Wiring 3 phase outlets - phase rotation convention?

richard newman · Apr 23, 2012

As I begin to wire up my new shop, I'm going to make sure that all the 3 phase twistlock outlets have the same phase rotation, so i can plug any machine into any outlet and have correct rotation. I've seen phase rotation indicators that show clockwise or counterclockwise, and I'm wondering if there is a convention as to which way to hook up the receptacles. Do L1, L2, L3 go to X, Y, Z respectively?

Or am I thinking about this too much and you just do whatever and correct by swapping leads in the plug, which is what I've done in the past.

stuball48 · Apr 23, 2012

Do what you have done in past.

Ohio Mike · Apr 23, 2012

Do you have "real" three phase or are you using a RPC? For all my stuff (which runs on an RPC) I made sure that the wild leg was always the red conductor and that the red conductor is always opposite the ground on the plug. So on an outlet or plug of any kind the red is straddled by the white and black conductors. This allows me to always make sure the wild leg is never used for a transformer or a control circuit. If you always wire the same pattern say Black-Red-White-Green then you should be good to go.

wgnrr1 · Apr 23, 2012

Everything of mine is wired exactly the same. Started in the breaker panel with all the same 3 wires, same left to right then 1-2-3-1-2-3 down. Then every plug is the same, I drew a diagram that lives in the box of plugs. If I need to change phase rotation, I do it inside the contactor box. I can plug any machine into any outlet, and it will run the same.

Josh

jmead · Apr 23, 2012

All the SO cord I've used has white opposite green and red opposite black, so white is a natural fit for L2 across from ground, and red & black for L1 & L3. No hassle bending wires around each other inside a plug.

richard newman · Apr 24, 2012

Thanks for the replies. I do have real three phase service.

wgnrr - that's what I was planning to do also.

jmead - I just put together a long 12/4 extension cord so I could use some machines, and noticed the same thing. And it works for the receptacles too.

rons · Apr 24, 2012

It sounds like you will not be getting this work inspected. Otherwise you would get your answer
from the inspector not here. But I don't have anything against that. Keep the wires consistent
with connections on the outlets. If I were so concerned about this I would look inside a 3 phase
panel at some business and go to a electrical supply store. Plenty of electricians love to talk
about this stuff and all you have to do is drink a cup of coffee with them.

REA · Mar 5, 2020

Yes, Jmed that is the way I have mine. Thank you for you input to this as I am setting up so the plugs are all the same. It has been a while since doing anything as been in the field repairing machinery for so long forgot about all the wiring done years ago.

kazlx · Mar 5, 2020

Like others have said. Just make sure all the hard wiring matches outlet to outlet. Then, if I bring in a new machine and wire up a plug, I check it and adjust machine wiring to match the outlet so the phase is always correct.

matt_isserstedt · Mar 5, 2020

As long as you are consistent it shouldn't be a problem.

Even if you are inconsistent it will still work but you'll have to phase-adjust 2/3 of the population of new machines entering.

The problems will arise with inconsistency when you move stuff around or use an extension cord.

EPAIII · Mar 5, 2020

REAL three phase? That's cheating!

I worked in a building with real three phase: well, more than one really. I never saw any hint of any markings of the order of the phases. I don't even know if a run-of-the-mill electrician would have any way to determine what they are in any absolute sense. I would think that a multiple channel oscilloscope would be needed for that. But perhaps there are other instruments. Or the drop from the pole pigs or those transformers themselves could be marked and could be traced from there.

If I were you I would just use the color coded wires in standard cable and wire all the sockets the same: a local standard for your shop. And no test equipment would be needed for that. Frankly I think this is what most electricians would do. Then, when you try out your first machine in one of the outlets, if it runs backwards you can just change it's wiring and it will work correctly in all of them. Ditto for each successive machine. However, if you know that all your 3 phase machines are already wired in a matching manner, you could swap two phases at the breaker box instead and then all of them should be correct. Changes in the breaker box are probably easier than in the outlets.

richard newman said:
Thanks for the replies. I do have real three phase service.

wgnrr - that's what I was planning to do also.

jmead - I just put together a long 12/4 extension cord so I could use some machines, and noticed the same thing. And it works for the receptacles too.

atomarc · Mar 5, 2020

Don't know is this is the gist of these recent posts, but there is an inexpensive device often used called a phase rotation tester..although for almost 30 years I played a game with myself whenever hooking up a 3 phase motor regarding which direction it was going to run. For some unknown reason I guessed correctly about 90% of the time...lucky me.

Stuart

TDegenhart · Mar 5, 2020

Electricians often run the same color, black, then use colored tape to identify the phases. For instance, when wire is brought in from the outside, all the wiring is black. The neutral is identified with white tape.

Tom

S.C. · Mar 5, 2020

The wiring is generally done like this
Phase A = Y
Phase B = X
Phase C = Z
Ground = G
I just realized this thread is 8 years old!! :willy_nilly:

I’m sure it will help someone though

johfoster · Mar 5, 2020

Yes old thread haha. I wouldn't have noticed had it not been mentioned.

What 3ph equipment would be getting moved around so often, and so quickly that it would be more convenient to methodically rewire the infrastructure...instead of taking 3min to switch two wires at the machine?

Dan from Oakland · Mar 5, 2020

The only code requirement that I'm aware of for 240 V Delta is that the high leg is identified with Orange phase tape and the neutral, if present in the box has white phase tape or white insulation.

thermite · Mar 5, 2020

Dan from Oakland said:
The only code requirement that I'm aware of for 240 V Delta is that the high leg is identified with Orange phase tape and the neutral, if present in the box has white phase tape or white insulation.

Minor nit, but if there is a Neutral presented, it is generally Wye, not Delta!

Mind - it may be a re-derived or "local" Neutral off a Delta-Wye transformer as mine is.

Dan from Oakland · Mar 7, 2020

Might be your nit- not mine. Its pretty common to pull a neutral in a conduit run with the 3 phase conductors regardless of Delta or Wye service so that a single phase 110 V load can be serviced. I said "if present in the same box". Ya still need a neutral for your single phase loads regardless.

EmGo · Mar 7, 2020

Dan from Oakland said:
Its pretty common to pull a neutral in a conduit ...

Conduit .... hmm. Sounds interesting. Is this some new thing they came up with ?

thermite · Mar 7, 2020

Dan from Oakland said:
Might be your nit- not mine. Its pretty common to pull a neutral in a conduit run with the 3 phase conductors regardless of Delta or Wye service so that a single phase 110 V load can be serviced. I said "if present in the same box". Ya still need a neutral for your single phase loads regardless.

Do yah now? I would not. Separate single-phase service branch, rather. Better-yet, avoid the need by staying at 2XX VAC, ELSE drop to 24 VAC off a transformer for controls & c.

1XX VAC is referred to just WHAT in a Delta service?

"It depends" yah?

Why d'you think I "voted" with my bankbook to provide Wye service and a re-derived "local" Neutral that is always at equal-potential, ANY hot leg above Neutral OR PE? HIGHER than the usual 120, yes. But at least all are the same or near-as-dammit ("generated leg", etc. applies..), there's no "corner grounded Delta", hence no "high leg" nor "stinger".

Nether of an RPC nor a Phase-Perfect - naturally "Delta" output, the both of them - is otherwise predictable for that, all legs, nor meant to be directly utilized that way for 1XX loads.

If you need 1XX, single-phase off a 3-P Delta service?

Proper way to provide it is with a 240:120 full-isolation transformer inside the envelope of the served "system". Keep in mind the secondary will be floating, not PE/ground nor Neutral referred, either.

ELSE a Delta transformer as has a "lighting" tap for such needs OUTSIDE the end-Luser equipment demarc.

Which is not the same as "full" Wye, be it 208 or higher.

Wiring 3 phase outlets - phase rotation convention?

Titanium

Stainless

Titanium

Hot Rolled

Hot Rolled

Titanium

Diamond

Plastic

Hot Rolled

Diamond

Diamond

Diamond

Diamond

Plastic

Attachments

Cast Iron

Titanium

Diamond

Titanium

Diamond

Diamond

Similar threads