OT: Need 110V from 220V 3ph

[snaggletto]

Ok, here's what I've got;

As I mentioned I have 4 large wires coming into my main panel and a smaller ground wire.

The 3 hot wires go to the circuit breaker terminal in the center. From left to right, A, B and C...

A to B = 241V
A to C = 246V
B to C = 247V

The 4th large wire goes to the 'white' bus bar/terminal strip. This terminal strip is mounted to plastic standoffs and *appears* to be electrically isolated from the metal frame of the enclosure. This wire is labelled as D...

A to D = 123V
B to D = 211V
C to D = 122V

The 5th smaller wire goes directly to the 'green' ground bus bar/terminal strip. This strip is mounted directly to the metal enclosure and is not isolated. This wire is labelled as E...

A to E = 123V
B to E = 211V
C to E = 122V

I've posted up some pics at my personal webspace of my electrical panel, my electrical meter outside, and one of my Dongan 240/480 X 120 step down "industrial control transformers."

http://members.cox.net/snaggletto/meter
http://members.cox.net/snaggletto/panel (make sure to zoom in)
http://members.cox.net/snaggletto/transformer

Hopefully this will answer some questions for you guys, and we can take this to the next level. Thanks for your time and tips.

 

[Newton W]

[I'm wanting to get my 120V from my 4 conductor 240 3ph power cord. This way I don't have the need for 120V power cords or big and hot step down transformers etc...]

Looking at your pics and your voltage readings, It's possible to achieve your goal, but it would take 5 wires.

A, B, & C would be your three phase 240 needed for your motor.

A & D would be used for your 120v

E would be your equipment ground

That would be 5 wires - one each for A, B, C, D, & E.

At the power panel:
1) You would connect A, B, & C to the three phase breaker.
2) D would connect to the Neutral bar (white wires)
3) E would connect to the Ground bar (green wires)

At your machine:
1) A, B, & C would connect to your line side of your motor starter or what ever type of motor controller your using.
2) "A" would connect to your PC, servo power supply, and controller boards as your 120v (Hot, L1...)
3) "D" would connect to your PC, servo power supply, and controller boards as your 120v (Neutral, N, L2...)
4) "E" would connect to some type of ground lug on the machine case.

Note:
If the 120v devices are not individually fused, I would suggested fusing them individually.

Make sure that the loads are properly calculated and your wire size and overcurrent protection are sized correctly.

Generally on a 240volt 3phase Delta connected system (like you have supplying your panel) the center phase is called the "high leg". I believe that the NEC requires it to be identified with Orange.

As mentioned before - Do Not use the grounding conduter as the neutral for your 120v devices.

Hope this helps,
-William Newton

 

[leitmotif]

Wutugot

OK looked at photos and herew is what you have
1. Based on the meter you have 4 wire 3 phase 240/120.
2. The meter class is 200 which I believe is ampere rating FOR METER ONLY.
3. Looking at wires in panel I do not think these are 2/0 (or larger) so you DO NOT have 200 amp service. I would guess maybe 100.
4. Wire "B" is your wild leg. DO NOT USE THIS for any 120 volt load. Voltage is too high and you will burn it (load) up. Volts on this seem a little low to me but I would have to calc it and am too lazy. Technically all "B" wires should be labeled with orange tape.
5. You can connect 120 V single phase load to a breaker on A or C and to neutral.
6. Be VERY careful to balance loads. You need to ensure that the total load (and "as used") load do not total more than the service entrance conductors are rated for.
7. You need an electrician who is familiar with this wiring method. Recommend an industrial or commrcial - residential does not have experiece with this

Dan Bentler

Ok, here's what I've got;

As I mentioned I have 4 large wires coming into my main panel and a smaller ground wire.

The 3 hot wires go to the circuit breaker terminal in the center. From left to right, A, B and C...

A to B = 241V
A to C = 246V
B to C = 247V

The 4th large wire goes to the 'white' bus bar/terminal strip. This terminal strip is mounted to plastic standoffs and *appears* to be electrically isolated from the metal frame of the enclosure. This wire is labelled as D...

A to D = 123V
B to D = 211V
C to D = 122V

The 5th smaller wire goes directly to the 'green' ground bus bar/terminal strip. This strip is mounted directly to the metal enclosure and is not isolated. This wire is labelled as E...

A to E = 123V
B to E = 211V
C to E = 122V

I've posted up some pics at my personal webspace of my electrical panel, my electrical meter outside, and one of my Dongan 240/480 X 120 step down "industrial control transformers."

http://members.cox.net/snaggletto/meter
http://members.cox.net/snaggletto/panel (make sure to zoom in)
http://members.cox.net/snaggletto/transformer

Hopefully this will answer some questions for you guys, and we can take this to the next level. Thanks for your time and tips.

 

[TConnolly]

Snaggletto
Have a look again at the PDF file I linked to previosly on this thread.

That is definitely the kind of transformer you have (240 Delta with a center tap and high leg). As you look at the drawings on it you can see meter readings that match what you have listed.

Edit to add:
Newton that is correct, the NEC requires that the high leg be either an orange wire or the ends marked with orange tape. Its also supposed to be the center wire on the breaker, which is what was described.

 

[Lancie1]

Guys,

Will someone please tell me which NEC article requires the "high" leg to be color-coded orange?

I think that "high leg" and "wild leg" are misleading names, because they imply that one phase of the transformer has higher voltage. In fact, all three phases on an unbalanced 3-phase center-tapped Delta secondary winding transformer have the exact same voltage phase-to-phase. It is the center tap on one of the windings that creates the 120 volts, and that is the only difference. Note that on this type of transformer, the 120 volt single-phase load is normally limited to 5% of the rated kVA, because that is the maximum unbalanced load that can be tolerated without overheating.

I think local practices are getting confused here with actual NEC rules. The closest I can find is NEC Article 210.4(D), "Identification of Ungrounded Conductors". This rule actually allows the user to select a color-code or identification method. Many electricians do use Red-Orange-Yellow for phases A-B-C. However this method is not universally accepted, so the color code or identification method has to be "permanently posted at each branch-circuit panelboard", a code requirement that is usually ignored.

 

[snaggletto]

Hey,

Now we are getting somewhere. A few more questions though.

1) At the bottom right, between the center PVC pipe coming into the panel box and the small armored flex conduit, there is a grey multi conductor rubber sheathed wire bundle coming into the bottom of the panel. If you trace it out you will see that the red/white/black go to the 3 pole breaker, but the 3 bare copper wires are going to the 'white/neutral bus bar'. This is the power cord for my 3ph air compressor that a 'qualified electrician' wired for me a long while ago. These bare copper wires should be going to the green/ground bus bar right? If the ground wire is going to neutral rather than ground, but the air compressor still works... what are the pros/cons of wiring it this way? Why would an 'electrician' do it this way? I'm trying to learn not just what not to do, but why.

2) See the pic about the transformer. This is a 2kva industrial control transformer. It's got a configurable 480 or 240 primary (2 pole input) and 120 sencondary (2 pole output). Recall I mentioned that it got really hot without any load before when I wired it up. I'd wired it up with two of the hot wires say like A and B. How should I have wired this?

Thanks, more to come I'm sure after I see some more responses. I love learning

 

[Eric Nelson]

Will someone please tell me which NEC article requires the "high" leg to be color-coded orange?

See the identification section of THIS page.

I concur with all the most recent responses from William and Dan. We had that type of service at our old facility. The high-leg was improperly marked with red tape, but probably because it's commonly referred to as the 'red leg' around here...



-Eric

 

[Lancie1]

Eric,

The code does NOT require an orange color for the so-called "high leg". What it does require is "orange in color or by other effective means".

Red is just as good, as long as it is well marked and documented.

 

[Lancie1]

Snag,

In your panel picture, your electrician has wired your ground wires to the Neutral bus. He probably got in a hurry and cut the cable too short and did not have enough bare ground wire left to reach over to the Ground buss. Many electricians think that the Ground buss and Neutral buss are interchangeable.

I once asked an electricain about his wiring practices. He said, "It's simple. Green goes to ground, and the other two wires are multiple choice!"

 

[Eric Nelson]

He probably got in a hurry and cut the cable too short and did not have enough bare ground wire left to reach over to the Ground buss.

I think that's EXACTLY what happened...

The code does NOT require an orange color for the so-called "high leg". What it does require is "orange in color or by other effective means".

Red is just as good, as long as it is well marked and documented.

Hey, Lancie. Care to join in our 'discussion' of NEC interpretation of ground conductor identification in THIS thread at Ron's?...



-Eric

 

[snaggletto]

"Hey, Lancie. Care to join in our 'discussion' of NEC interpretation of ground conductor identification in THIS thread at Ron's?..."

Yes, no thread highjacking please, ignorant people like me need education on the topic at hand!

Ok, so the electrician was lazy and wired the ground to the neutral. Expected around my neck of the woods, that's why I'm pestering you guys rather than calling another 'qualified electrician'.

I know it's wrong, but what does it hurt, or rather why is it so bad? Just the fact that the air compressor is not properly grounded? Is having the ground wired to neutral the same as not having it wired to anything at all? If the motor shorts out and the ground is wired to the neutral, then the frame of the aircompressor becomes HOT?

What about my #2 question about properly wiring my control transformer? Any takers?

I'm very persistent so I'll keep badgering until I get the answers I need. Thanks for help so far people.

 

[leitmotif]

TWO THINGS
Easy first

Lancie is right. In my 2000 NEC Art 384 Switchboards para 3 e
On switchboard ,,,,,, supplied by 4 wire delta ,,,,,,,,, with midpoint of one phasse grounded ,,,,,,, that phase busbar or conductor having higer voltage to ground shall be durably marked by outer finish that is orange in color or other effective means.

NOW FOR THE HARD PART the ground vs neutral in a panel and where do they go??
Ok, so the electrician was lazy and wired the ground to the neutral. Expected around my neck of the woods, that's why I'm pestering you guys rather than calling another 'qualified electrician'.

I know it's wrong, but what does it hurt, or rather why is it so bad? Just the fact that the air compressor is not properly grounded? Is having the ground wired to neutral the same as not having it wired to anything at all? If the motor shorts out and the ground is wired to the neutral, then the frame of the aircompressor becomes HOT?

Now for the hard part
Ground and neutral are supposed to be at same potential to ground.
1. Tecnically they are the same
IF and only IF
there is only one panel ie the main or service entrance.
Reason is the neutral is bonded to grounded electrode conductor at the main panel. So is the ground conductor. They are often seen on the same buswork (neutral buss)
2. In a secondary panel (fed from main)
The neutral bus is floated ie insulated from ground.
The ground buss is tied to the panel.
REASON if neut and ground are tied togehter in 2nd panel they are in parallel and will share neutral current. This is OK until you disconnect a ground that is carrying current
- most embarrysing
BUT if there is enough current you WILL NOT be constipated for a week.

Have your next electrician tape the neutral white and splice if he has to (not supposed to splice in panels but lesser of two evils) AND connect to neut buss. Better yet have him repull the circuit.

Now it sounds like you are bound and determined to do this yourself.
1. Please put me in your will
2. Call the utility and make sure your service does not have CTs for metering. IF this is the case you can pull the meter to deenergize panel (CHECK WITH UTILITY to make sure I am right)
3. OPEN all circuit breakers
4. Check meter to ensure little wheel is not revolving
5. Set meter right next to you when working
6. Do your work
7. Check all breakers open still
8. Reinsert meter
9. Call eletricin to make sure you got it right
10. Shut breakers

Dan Bentler

 

[TConnolly]

Here is the relevanat paragraph fron the NEC

Note that it mentions "where the midpoint of one phase winding isgrounded"

Dan is spot on - The neutral is grounded, but it is not to be a ground conductor. A seperate ground conductor is required.

 

[Eric Nelson]

As I said before, Lancie is probably right about this happening because of the laziness of the electrician, but I can think of one other possibility (which is also scary)...

The compressor is 3-phase, and most likely uses a contactor to control the motor (do they even SELL 3-pole pressure switches?). Now, is the contactor's coil voltage 120V or 240V? IOW, is one side of the coil connected to ground? I only mention this because I've seen **** like this done all to often...

I've also seen WAY to many instances where the ground and neutral are bonded in subpanels. Damned 'electricians' feel that since the panel came with a neutral bonding screw, they HAVE TO install it...



-Eric

P.S. Having the ground wire(s) tied to the neutral bus is just wrong, wrong, wrong. BUT, it's better than being connected to NOTHING!

 

[Eric Nelson]

What about my #2 question about properly wiring my control transformer? Any takers?

Gerry offered a few suggestions back in Post #12. The catalog page from Dongan is HERE. They show the proper wiring at the end. Do you have the jumpers installed properly? For a 240V primary voltage, the jumpers should be installed in the parallel configuration:

-Eric