Need Advice for New Shop Power Setup 480/208V 3 Ph With Unique Grounding

After seven years of being in Los Angeles, and after another year of having my machine tools in storage, I will be able to set up shop in a good location (FINALLY).

I’ve already been in business by myself for nearly a year, just barely managing to get by without the use of these tools (like having one arm tied back). So I’m really looking forward to being set up properly.

I would like some advice for the very knowledgable members on this forum regarding how I should set up power in my shop:

The supply to the building is 480V 3 phase. There are three 480:208V transformers in the building. Two 75 KVA in the electrical room (SW corner of building), and one 112.5 KVA in the room where my machine shop will be situated (SE corner).

In the room I will be setting up my machines (we’ll call it the machine room) there are two 200A Siemens panels fed from that transformer. One is set up for mostly single phase loads. The other is set up for 3 phase loads but does not have any 3Ph loads connected. Both have plenty of space available for additional circuits.

Here’s where it gets interesting: There is a ground rod driven into the floor in the corner of my room. The transformer is grounded to that. Also connected to it is a long strip of copper, about 3/4 by 1/4 that runs for half the inside perimeter of the building. Apparently there were building equipment in there thaw was static sensitive so it’s a low-resistance ground.

I took a look inside the panel that I would be connecting my 3 phase loads to (initially there will be only one). It has the three power lines, plus neutral, but no ground. The ground and neutral bars are bonded together and being used as neutral.

Regrettably I must add: Funds are very tight and I have to fund anything special to my needs myself. So I have to choose the least costly path that is safe and that gets me working and making money. There is always the possibility of upgrading the setup in the future.

Questions:

1) Should I be concerned there is not a dedicated ground on the panel I will connect my 3 phase load (2hp Schaublin Lathe) to? I’m assuming the conduit and case of the panel are ground. Does it matter that I intend to add an inverter drive to my lathe?

2) The company I’m partnered with that signed the lease and is paying for most of the renovation wants to remove the copper strip to turn it in for recycling value. I told them I want to keep the strip in my rooms, and I have my own ground rod.

But the strip also connects to the grounding in the electrical room. Will there be any issues caused by breaking that connection? Should we at least run a ground wire to replace the copper strip?

3) My Schaublin has a 380V 50 Hz motor. For now I plan to use a 208V 3 Ph input and the machine’s built-in step up transformer. But I’ve wondered about the possibility of eventually powering the inverter I plan to add (a 460V GE unit) from the 480V power. But I don’t know how to properly set that up.

I imagine that the 480V power could be accessed at the point it enters the transformer case. But would that require another panel box or other requirements?

FWIW - there is a 5HP Ingersoll-Rand air compressor thats 460V 3 Ph in the electrical room. It appears to be connected to the 480V power as it enters the building, in box mounted ahead of the transformers.

ALSO: If anyone that reads this is in Burbank/Glendale CA area and knows a electrician that could do the work for me for reasonable cost, please let me know. At this point I would just need a single 3 Ph outlet connected, close to the panel, and maybe two 208V single phase outlets in the room.

And if anyone can give me an idea of what a very straightforward job of setting up a single 3 ph outlet and one or two single phase outlets, please let me know. It's important to have some perspective on cost.

Thanks in advance for your advice!

The purpose of the Ground leg is to provide a path for a faulted electrical system back to earth that does not flow through the operator.

The purpose of the Neutral leg is to return out of phase current to the panel.

They should not be tied together except at the entry point of the service.

You should have no trouble running a Schaublin with neutral floating or tied to ground, except if you have an FI breaker at the lead in to your distribution panel (as is Law under IEC).

Tying ground to neutral will trip the FI.

Stick with the Schaublin's step-up trafo, or have the motors rewound.

Things are different in the US.

After a transformer you HAVE TO re-establish a ground and neutral connection, according to the NEC. it is a "separately derived service", with NO "metallic connection" to (in this case) the 480V side. In effect, the transformer establishes a separate local "service".

That secondary may be grounded to rod, to building steel, or even back to the building earthing system, depending on what is available. A good ground is the reinforcing rod in the foundation, which building steel may go back to, or another purpose-made conductor buried in the foundation. Obviously on the 44th floor of a building, the steel is all you have.

If your local box has the box ground going to the rod, and neutral from transformer bonded to that, it is correct. That re-establishes a ground source (the rod) and bonds the neutral to it, which should be done inside that breaker box, which is effectively your "local service".

Do you mean to say that is NOT what you have?

If there is no connection from the box and local neutral to that rod, or to some other ground/earth source, then it would seem that there is a violation right there.

As for the anti-static strip, it is not (we assume) associated with the electrical service, and is just a source of static drain to ground. The rod presumably was just a convenient ground. Any grounding method should be fine for that, but do not confuse it with any electrical ground. Static grounding cords to people should have (and it is usually in the cord) a resistor of at least 1 megohm in series.

It may be best to run that static ground back to the electrical ground rod, just because that assures all things are at the same ground potential.

cinematechnic said:

2) The company I’m partnered with that signed the lease and is paying for most of the renovation wants to remove the copper strip to turn it in for recycling value. I told them I want to keep the strip in my rooms, and I have my own ground rod.

But the strip also connects to the grounding in the electrical room. Will there be any issues caused by breaking that connection? Should we at least run a ground wire to replace the copper strip?

Click to expand...

Cannot be sure just yet. Obvious that you want to remain on good terms, given their position, but friendly enough to ask them to wait until a licensed electrician has confirmed that it is OK to cut back.

Otherwise, present-day cost of recovering from an overly-greedy 'pruning' and having to put in NEW copper will for-sure exceed scrap value of the OLD copper.

Bill

Without inspecting the setup one can only guess. From the description is sounds as though the two, 200 amp
panels do represent a service entrance at the secondary of the transformer, what was described as a 'separately
derived service.'

Around here in industrial applications a made electrode (ground rod) is not sufficient but rather the bond (tie between groundING
and groundED conductors - white and green wires) for the secondary of the transformer should ideally be carried back to the
480 V service entrance ground point. This may be the case in your installation
but until an electrician inspects there is no way to be sure.

This is a bit of a fine point in the code and it has been changed recently I believe.

The authorities having jurisdiction don't care about your finances.

Poor people are just as suitable for electrocution as wealthy people.

You have surplus information in this query; is this perhaps a question from a test?

You will need properly sized breakers.

You haven't told us things we need to know, but I'll suggest you apply for a credit card if you don't have one, before you proceed.

Just set up twist lock receptacle at the panel, for an extension cord to power a specific machine.

Yes, twist lock plugs and receptacles are expensive, new or used. Put them on your charge card.

I doubt anyone has them to give you for free. Except...You are in Hollywood, perhaps the only place on Earth where extreme-duty extension cords are used all over the place (movie studios), maybe a local has stuff to give you?

You will most likely buy the cord/cable new, not used. Put it on your credit card. You can find all of this stuff on ebay.

His location indicates North Hollywood. Completely different world from Hollywood, although not too far away geographically. This statement "The company I’m partnered with that signed the lease and is paying for most of the renovation wants to remove the copper strip to turn it in for recycling value." Given your location I'm very surprised any copper not connected to high voltage is still in place. Scrap prices are down, so keep it there as long as you can. A ground bus like that would be nice to have if you can keep it.

While they are scrapping out the copper, take out the sprinkler system and the fire- rated doors.

I would say tearing out the copper bar falls under "never sell your tools". draw the line now and if partner insists you have found out early on your partner will step over dollars to get at nickles

Lots of odd things, and some missing info.

Odd: You have a lease, and the copper strip is apparently attached to the building..... Generally, improvements that are attached become the property of the building owner. Why your business partner thinks he can scrap out that copper I have no idea. Does he also think there are too many roof trusses,and some of those could be scrapped? How about plumbing?

And, even if he does scrap them put, the conduit for any circuits that run in the area will be just as good a ground as the copper for static control purposes. For certain things, audio facilities, etc, the copper strip may have been better.

Missing....

You have a 112 kVA 208V transformer in your area that will supply 120V and 208V 3 phase. That should be plenty of power. Does it have circuits of 120 and 208 running to where you want them, or at least where you can use them?

If you want to have more circuits, that would seem to be straightforward addition to the electric system. The electrician can determine if the grounding is OK at the time, and if he does not, the inspector will. (Better the electrician does). Is there some problem with adding circuits?

There is apparently neutral and ground, and some form of ground connection/rod. One has to assume that the installation passed inspection at one time.... it sounds as if it has what it needs. Why exactly have you decided that there is a problem?

You seem to have a step-up transformer in the lathe already, which would power the VFD/motor combo just as well as the motor directly. Why do you think you need more?

As for costs, it has been a number of years since I was last involved with construction issues. Back then we figured every outlet cost about a hundred bucks. It has probably gone up considerably since.

Guys, thanks for the input and sorry I've been away. Been working 7 days a week on this project + regular work + a consulting job (that I'm way behind on), etc.

Today I'm using the excuse of a heavy rain day to take Sunday off. Yes, it's raining heavily in drought-stricken CA.

SteveBausch said:

The authorities having jurisdiction don't care about your finances.

Poor people are just as suitable for electrocution as wealthy people.

You have surplus information in this query; is this perhaps a question from a test?

Click to expand...

This forum has been very helpful to me, I would never come on here under false pretenses. Perhaps I misunderstand you?

Agreed on safety - I was not planning to do anything unsafe. Why would I bother asking questions on a forum if I was just going to "ghetto rig"? But it is an important point and worth mentioning.

Yes to twist locks (N.O.S. Hubbell are available for reasonable prices on fleaBay), and heavy extension cord (already have enough). Reluctant maybe on the charge card thing. I'm already nearly tapped out. Not easy to start a business in the People's Republic of California and I just barely got through last year.

JST said:

Lots of odd things, and some missing info.

Click to expand...

Understood, hopefully this will clear some things up:

I'm currently working on adding some windows to the two rooms and planning the electrical. The low resistance ground (1/8 x 3/4 copper strip) was removed EXCEPT in my two rooms. Fortunately I have a ground rod in the room that will be my machine shop, so it is a good ground. I expect I would make use of it for static control just as the previous tenants did.

The 112.5 kVA transformer is connected to that ground rod (which is right next to it). Input is 480V 3Ø, output is 208V 3Ø.

The two Siemens panels fed from the transformer in my room are 200A and 150A respectively. The 200A panel is set up for 3 phase loads but has none connected, nor any 208V single phase loads. More than half the slots in each panel are unused and available. They are all regular lighting and outlet loads on 20A breakers.

The panels are fed by 3 phases and neutral and have ground and neutral bars connected together. So it seems the conduit is ground.

The low resistance ground copper strip is connected to the ground rod and nothing else.

There is an electrical room on the other side of the building with 2 similar transformers and a ground rod.

Here are my questions for now:

Q1:

There was previously a copper strip connecting the two ground rods that has been removed. Should the two ground rods be tied together with a ground wire? Or does that not matter? The rods are about 60 feet apart.

All the loads in the building are on the 208V side of the transformers except for the 460V air compressor, which is fed directly from a large box just outside the building (service entrance).

Q2:

I want to add a 208V 3ØY outlet in the room that will be my shop. It will have its own conduit running to the 200A panel (a run of not more than 15 ft), should that circuit have a ground wire to provide a low impedance path to ground (rather that just grounding off the steel conduit)? In other words, a 208V 3ØY isolated ground outlet.

Q3:

I have a box that has two independent dedicated 120V 20A circuits (two hot wires black and blue, two white neutral wires)connected to the 200A panel. Is there any reason why I could not to create a 208V 20A single-phase outlet? One white wire for neutral and the other used as ground and marked with green tape at both ends (the box and the service panel).

In this box's location, the wire has been run in flex conduit, so it would not be feasible to add extra wire.

Thanks!

The transformers are there to feed the 208.
You say neutral on your 3 phase feeds ... neutral to what? This is not a house.
Bonding to local ground rods was very common in the past to keep noise out on the small signal side as it is hard to depend on the connection to the main and it may be carrying some current that screws you as each connection is not perfect and any wires no matter how big have resistance.
Transformers in the loop are always bad for your electric bill. They get warm, where does that heat energy come from?
All fine if added heat in the winter where it helps as a piss poor efficient heater .... summer comes and often you fight it with AC adding more money. Yes it's not big but .........pennies count and in a big plant it is no longer pennies.
There is no neutral in a 3 phase system and it's relationship depends on your service type.
Ground is there to stop you from being the ground rod for the floating power through your boots.
Not bonded good and your operators will complain about random pokes and while they are just once in a blue moon and not repeatable take these very seriously.
Machine grounding or bonding to ground is a very complicated subject that seems simple but is not.
Google ground loops and be ready to be confused.
One can grab a hot 440 3 phase high leg wire and you feel nothing if you do it right.
Squirrels run down hot power lines all day long just fine and dandy. Birds sit on way high voltage lines.
Bob

Neutral on the 208 is for 120V LODS.

DO NOT use the independent lines for 208. You need a two element "tied" breaker that turns all of it off for a fault on either/any wire. IOW, a dedicated 208V circuit.

I like a ground wire in the conduit. Conduit develops bad connections. Bond the ground wire to the box at the outlet.

Bonding the two grounds is likely a good plan. You didn't really need the rod, the conduits are grounded and would drain static if the thing were bonded to them. since this is a separately derived system, the main ground for the transformer should be pretty quiet, but that will not matter for a static drain ground.

JST said:

Neutral on the 208 is for 120V LODS.

DO NOT use the independent lines for 208. You need a two element "tied" breaker that turns all of it off for a fault on either/any wire. IOW, a dedicated 208V circuit.

Click to expand...

JST, thanks for the reply. I was planning to use a 2-pole breaker, I forgot to mention that.

What I want to take advantage of is the existing wiring and box in a desirable location that is about 30 feet from the service panel and in another room where it would be a lot of trouble to run a new line. Also, it is flex conduit.

I agree about ground wires in conduit. I re-wired my former house (back in Miami) that way. It had been built in 1950 and had no ground wires. I pulled new wire (hot, neut., grd.) in the conduit. Everything worked perfectly. My mini home theatre in particular, which had isolated ground, was noise free in both sound and picture.

We are running 1" copper for compressed air line. It is going from the air compressor (in the electrical room) to my workshop (where the transformers and C and D panels are).

Should the compressed air line be grounded?

Yes, even sheet metal shall be grounded.

SteveBausch said:

Yes, even sheet metal shall be grounded.

Click to expand...

OK, will do, easily done. I also convinced them to run a ground line between the two ground rods to substitute for the copper strip that was removed.

Workshop 1 Completed

I want to thank all the members that contributed by posting on this thread. Here's what I ended up doing:

The owner of the larger business that is the leaseholder on the building hired an electrician to do some work for him. I in turn made a deal with the electrician where I did the "grunt work" (installing conduit, cutting wires to length, etc.) and he did the final hook-up for my 3 phase outlet.

I ended up using a Hubbell 3ØY isolated ground outlet and ran both neutral and ground wires to the neutral bus on the service panel. It might be overkill but my lathe already had the 3ØY plug and I feel better knowing my outlet has a copper wire for ground (rather than just the steel conduit) since I will be running an inverter.

I kept the low-resistance 1/8 x 3/4" copper strip grounding in my two rooms. This will just be used for static control. Very useful if I end up working on sensitive electronics. This strip is connected to the ground rod in my room.

A 12 Ga ground wire was run connecting the two ground rods (other one is is the electrical room) that are separated by about 65 feet. This substitutes for the copper strip that was removed.

I've attached a photo of the completed room.