Wiring 3 phase Delta and 110 through NEMA L15-30 Plug?

Hey guys, new member here so go easy on me. I do sheet metal and welding fabrication for automotive applications and have just decided to expand into some machining, so will probably be posting here often.

Just picked up an ACRA vertical mill made in the late 80's. My space has 3 phase power according to the breaker box, but doesn't yet have the appropriate wiring/plugs ran to the space where it's needed.

The shop I bought it from had it hardwired in. I'd prefer to have it on a plug so I can move things around if needed. They had it temporarily wired just so I could verify everything worked when I got there and I snapped a picture of the wiring before it was disconnected to load up in my truck.



They had 5 wires going to it. Two (white and black) were the 110 that went to the power feeds, DRO, etc. and three blue wires were the 3 phase for the motor. After some googling I found that having just 3 wires for the motor means it's wired Delta, but frankly, building electrical is just about greek to me, so I get lost pretty fast here.

I'm going to have an electrician come in to run conduit over to a box on the wall where I'd like to have the machine. I know the electrician is going to be able to tackle the building side of things just fine, but I dont' expect him to know exactly how this particular machine needs to be wired up, so on the machine side I want to be sure I know what needs to be done. Here's what I'd LIKE to do, but I don't know if it can be done this way or if it's the 'right' way to do it... so hoping you guys can give me some guidance on whether I have this right. (or how wrong I have it!)

I would like to wire a few feet of flexible cable (10 gauge, 4 wire) coming out of this box on the mill to a NEMA L15-30 connector to match an L15-30 plug on the wall. Can I run everything - both the 3 phase and the 110 power source for the mill through a single 4 prong L15-30 connector? That would certainly make things easy instead of having two separate cables coming off the machine that have to plug into separate wall sockets.

The L15-30 connector has X, Y, Z, and G prongs. XYZ are the 3 phase power, and if I understand correctly then two of those are 110 and one is 220, so can I run the 110 stuff on the machine through either one of those 110 sides? G is ground, and it seems awfully strange to me that there is no ground for the motor, but as there is no fourth ground wire for the motor, can I just run the 110 item's ground on this pin?

As to the plug, you do not have enough pins to cover what you want.

And, what you want is pretty much not the best.

First, all 3 phase is not alike. Some IS as you suggest, 240V "high leg" power, with a 120-0-120V and a 3rd wire. Even with the "high leg" power, you would need a 5 pin connector, because you must bring in the neutral, 3 power wires, and the EGC. Some is a different type, such as corner grounded, which would NOT be suitable directly, and would need the separate 115V. And then there is 208V, which has 120V from any wire to neutral. the 208V would do all you need, 120V, and 208V three phase, all in one 5 pin connector. And 208V is a common sort of 3 phase.

Second, for separate 115V, a "115V" connection would be 3 wires in itself, 2 wires for the 115V and a "safety ground" (Properly called "equipment grounding conductor" or "EGC").
You would need 4 wires for the main power (3 power wires and an EGC), so the fewest wires that could handle what you want in one plug would be 6, sharing the EGC. That setup is at least "unconventional", and poses issues even of you found a suitable plug/receptacle to handle it. If you found a suitable plug type, there is nothing to say you cannot do that, but you'd be limited to plugging it in where there was one of those plugs installed, so not much advantage over hard-wiring.


The most usual way to do the job is to get one type power in on the plug, and develop any other voltages inside the unit, via a transformer, etc. That is simple enough for lights, control systems, and DRO, but the feed motors may likely require more current, and that would require a larger transformer.

It would surprise me a bit if the DRO could not accept 230V. The feeds, if they are separate individual add-on types might or might not accept 230V, many will not.

Maybe you can give a bit more info as to how much "115V" power you need, and what actual power type you have in the building. Hardwiring may be the most practical approach.

No. The plug/receptacle you have has three hots and a green wire ground. The green wire ground goes to the frame of your machine plugged in.
You cannot use that as a neutral for your 120 volt loads.

(another option would be to swich over to 5 conductor S cord and connectors with 5 contacts)

Or just place 2 outlets...

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I see over 5 code violations in your box already, better hire a electrician...what a mess...Phil

Phil in Montana said:

I see over 5 code violations in your box already, better hire a electrician...what a mess...Phil

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Really.

"I'm going to have an electrician come in..'

Just stop there. Tell him you don't know the "electrical code", but that you want EVERYTHING done:

"to code, and so it will pass inspection, even if the inspector has a hard-on that day"

... so you do not HAVE TO "know the code".

HIS "rice bowl" to know what will pass. And keep his ass AND your ass TF out of trouble. He will be able to tell YOU what you need in the way of breakers, fuses, disconnects, outlet box, plugs, sockets, type of cord. All that 'stuff" is what he does for a living.

Do NOT try to tell HIM.

His expertise is what you are hiring him for. He's a credentialed electrician, working within a regulated "system". Not ALL of his work has to stand specific inpection, but MUCH of it does.

Not the same thing as the guy who cuts grass, is that?.

Just let him do his job.

Generally faster and CHEAPER that way as well as safer and better.

Example...from an auto repair shop, years ago, but you can see how they feel:

OUR SHOP RATE: $ 50.00 per hour

IF YOU ADVISE: $ 100.00 per hour

IF YOU "HELP": $ 200.00 per hour

AND IF YOU WORKED ON IT FIRST: .......

Our shop had:

Answers: $10 each
Answers, requiring thought: $20 each
CORRECT answers: $30 each
Dumb Looks are still free

Phil in Montana said:

I see over 5 code violations in your box already, better hire a electrician...what a mess...Phil

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Not his box, as stated in the first post. Temporary, to power it up for the op.

My 2 cents...Wiring two outlets isn't a big deal. Wire the 15-30 with (3 hots and a ground), have a 110V receptacle handy. And a 110V power strip mounted to the back of the ram can supply your power feed and DRO's. For drilling a simple hole where location isn't critical, they're not needed. Leave 'em off, drill the hole, done.

Excellent idea to use a plug/receptacle combo, BTW. Code recognizes it as a disconnect, it's way cheaper than a disconnect, and to me feels more secure. A plug laying on the floor is more visually assuring than the position of a handle.

You can pull single phase off the incoming 3 phase and still be code compliant. Same plugs and receptacles. Very handy if running 220V single phase machines and the incoming has the right line to line voltage.

neilho said:

........

Excellent idea to use a plug/receptacle combo, BTW. Code recognizes it as a disconnect, it's way cheaper than a disconnect, and to me feels more secure. A plug laying on the floor is more visually assuring than the position of a handle.

.......

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On the other hand, a handle can be positively locked out easily, so that even a subnormal impatient manager cannot just turn it on. A plug needs a lockable cover/box/boot the right size for it.

Whichever.

I am seriously allergic to machines that have several power cords. Others may have a higher tolerance. (And you need too many "plug boots" to safety them.)

JST said:

On the other hand, a handle can be positively locked out easily, so that even a subnormal impatient manager cannot just turn it on. A plug needs a lockable cover/box/boot the right size for it.

Whichever.

I am seriously allergic to machines that have several power cords. Others may have a higher tolerance. (And you need too many "plug boots" to safety them.)

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Well. Not as if I needed a hundred of 'em. Nor even FIVE actually.. Not that many 3-Phase machines here, what with Dee Cee.

So proper "rated" and even US made "rotary" disconnects were found @ $25 to about $40, depending on Amperage.

Now I can leave the Hubbell Twist-Lock TF alone unless I NEED to move a machine.. and just make use of the disconnect right with it ..with lock-out tab.

At-machine end the cord is removable with a Hubbell as well - just opposite "sex".
Boxes for those come with covers built in.

Widely used to connect outdoor gen sets & such.

2CW

JST said:

...even a subnormal impatient manager cannot just turn it on.....

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Another fan of twistlock plugs and receptacles. When I do this at work I typically tie the cordage
tight around the impatient manager's neck to keep him in one place where I can see him.

jim rozen said:

Another fan of twistlock plugs and receptacles. When I do this at work I typically tie the cordage
tight around the impatient manager's neck to keep him in one place where I can see him.

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If you'd at least do it so his feet still touched the ground? There might still be somebody to sign off on the paychecks?

As neilho noted, my original pic just shows how the shop had it temporarily rigged up to show me the mill worked.

Appreciate your candor guys. I'm right there with you that it's important that it be done right.
Electrician came by yesterday to take a look at the job and he's working up a quote. We're going to have two cables coming off the machine; an L15-30 and a 5-15.

thepass said:

Appreciate your candor guys. I'm right there with you that it's important that it be done right.

..
Electrician came by

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Cornishman I worked with for some years:

"Why would I keep dogs if I had to do the barking myself?"

thermite said:

If you'd at least do it so his feet still touched the ground?

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On advice of council I decline to answer that question.

Good to hear an electrican is on the job for him. It's the right thing to do.

JST said:

On the other hand, a handle can be positively locked out easily, so that even a subnormal impatient manager cannot just turn it on. A plug needs a lockable cover/box/boot the right size for it.

Whichever.

I am seriously allergic to machines that have several power cords. Others may have a higher tolerance. (And you need too many "plug boots" to safety them.)

Click to expand...

I regard lock out, tag out as one of mankind's most noble inventions, especially since I often work on machines large enough that someone trying to run them cannot see me on the other side with a handful of wires.

Bill

9100 said:

I regard lock out, tag out as one of mankind's most noble inventions, especially since I often work on machines large enough that someone trying to run them cannot see me on the other side with a handful of wires.

Bill

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It can be educational over-done just as easily as under-done. But at least yah live to tell the tale.

Must have been about twelve or thirteen, and a tad smart-ass snotty. Already.

Dad - Corps of Engineers, and "Inspector" a good deal of his years, was about to teach me how to solder the wiring (that long ago, it was..) for a new wall-mount light fixture, second floor.

"Safety first!"

So he ran my agile young ass clear down to the basement and had me carry back for his sight both of the pull-out cartridge fuse block holders that powered the whole dam' house.

Then grumbles that the trusty 100 Watt soldering iron he had relied on since 1936 must have finally run its last race. Old ugly just set there. Dead cold.

Ran my young ass up and down stairs twict more to make sure none of the plug fuses DOWNSTEAM of them two master entrance block holders had blown.

Finally, sassy as I was, I suggested I bend over, he could line up and kick me right square in the ass.

Then HE was to bend over, and I would be permitted to return the courtesy, "rank" suspended temporarily for the exercise.

"What has gotten into you NOW?"

And I waved both of them cartridge fuse blocks up into eyeshot.

"Should I go and get the Bernz-o-Matic torch? It doesn't NEED electricity."

We settled for red faces. Ass-kicking is just too much like work.

JST said:

On the other hand, a handle can be positively locked out easily, so that even a subnormal impatient manager cannot just turn it on. A plug needs a lockable cover/box/boot the right size for it.

Click to expand...

All true. Point taken if one is working in a shop with lots of people and can't see the plug/disconnect. Different here in that I'm a one man shop.

neilho said:

All true. Point taken if one is working in a shop with lots of people and can't see the plug/disconnect. Different here in that I'm a one man shop.

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We think we are.

But we are not always the "same" one-man .. when we shift mental gears to take up a different role or temporary tasking. Some we have great habits of safe working. Others, less-so - or simply less experience than we think we have.

JMNSHO, but it seems EASIER and more likely a body can screw-up and have an accident when working alone than when operating as part of a team of even just TWO souls.

And there is no one else there to take a 2 by 4 and knock yer ass loose of the 'lectricity... drag you out of fumes . lift a crushing weight.. Or whatever...

So.. I tend to OVER do it on safety in a "one man" shop. Not cut corners.

2CW.. and @ 75-plus years and still counting.. (Dad 92, G'dad 89..etc.)

"Your Mileage May Vary"

And there is no one else there to take a 2 by 4 and knock yer ass loose of the 'lectricity... drag you out of fumes . lift a crushing weight.. Or whatever...

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yup, so true. Working in the woods alone even more so...

But working alone in the shop, I know that if I disconnected something out of sight, it's gonna stay that way till I do something about it. Other idiots behavior not a factor.

Good chance to practice all those safety habits, too. Done OK so far, only two near death experiences in 50+ years of working - uh-oh. Start of another thread.