Electric Wiring Question

In the shop where I work, we have a 220 volt Baldor grinder and a 120 volt Baldor buffer. We needed to relocated these so I had to extend the conduit and wiring. The grinder (220) has two hot wires going into the switch and 1 white wire that is connected to a grounding screw in the back of the metal switch box. The buffer (120) had its own separate hot wire and then the same white wire from the grinder continues and goes to the buffer's junction box. The buffer's motor only has two wires - black and white. Everything worked fine before I relocated and everything works fine now but I am wondering if this is ok and safe?

Well I'd say it's not really right or even safe. The white wire that runs through to the beffer should not be attached to the screw on the back of the box. However there should be a green wire running through that conduit connecting the boxes to be really safe, although it was legal at one time to use the conduit for the ground it sometimes becomes corroded or broken and then you lose your ground path. If the conduit is all in one continuous run I would take the white wire off of the screw and tape it up, or better yet have an electrician look at it to see if there is a reason this is wired like this(conduit broken behind a wall or something). Just my $.02

It was legal a few generations of code ago - 1980's or so???

Since you disturbed it, not right or to code now.

The 220 machine needs 2 hots and a ground.

The 120 machine needs a hot, a neutral, and a ground.

To wire both machines, you'll need 4 wires.

Sharing the nuetral & ground is wrong - we've learned that it can create energized loops that are more dangerous than not having the ground at all in the wrong situations.

You'll probably need to start at the main box & follow all the way to get it sorted out right, if you do sort it out.

You'll get a lot of advice as to whether to just leave it as it's worked this way for so long; to you will kill everyone who touches the machines next.....

To answer your question, it isn't right the way it is. What you do with that answer is up to you & your insurance company.

I'm just a simple dirt farmer, so if my general comments don't quite add up, I don't know it all on electric for sure myself.....

--->Paul

Listen to Paul. He has it all correctly figured out and explained.

Good advice. Call electrician, please. Sooner the better. Worked with 2 people fried because of junk like this. State interrogated me for 1 week. It was not my doing at all but I had to satisfy them that company was responsible. Greatest nightmare you could ever have. Situation was ungrounded fluorescent lights and fluorescent lights with no switch to turn off. 35 years ago, but like yesterday. Still dream of this insanity. Dave

Thanks for the replies. Thats kind of what I was thinking... The buffer and grinder each have their own breaker. On the 120v buffer, where would I attach a ground wire, there is no terminal currently - somehow add a grounding screw to the existing junction box? I can use the same grounding wire for both machines, correct?

Also just thinking - how does it work when the ground wires and neutral wires all attach to the same bar in the service panel? I guessing its because we are mixing 120 and 220?

Depends. It's a common error for the ground and neutral wire to be bonded together in remote panels. Anywhere except at the meterbase/utility transformer, unless the distribution panel is within a few feet of the meter base.
Sub panels and panels in multiple buildings supplied from the same transformer.Should not have the neutral and ground bonded. I particular where livestock are concerned.
That said the ground from the sub panels is supposed to be connected to ground rods. At the remote building and a 4th wire, a ground run back to the meter base.
Problem is a neutral carries current and suffers voltage drop. If bonded to ground, now the ground system carries neutral current or at least elevated in voltage above true earth potential. A volt or two is all that's required to stress livestock.
A neutral isn't neutral, it's just called that.It's complicated but the neutral is an insulated current carrying conductor. You don't want it tied to and energizing grounded metal .

The neutral wire carries electricity back away. It needs to be grounded to earth.

The ground wire - in a perfect world - is never used or needed. However _if_ it's needed, it might save your life or keep from burning something to the ground - or less dramaticly save your $29 electric drill from fizzing itself.

The ground wire needs to bleed electricity to earth, so it too needs to be bonded to earth.

Turns out a good place for both the neutral & the ground wires to bond to earth is in one location by the main panel. From this location, you should run seperate ground & neutral wires.

If the ground & nuetral ever get bonded together anyplace else - then it sets up odd loop (curcular) connections that don't fail properly. It sets up conditions where any electricity on the neutral wire _also_ now is carried by the ground wire. This makes all your bare metal everywhere possibly electrified....

Put it another way. You have 2 pipes running through your house, one is hot water and one is cold water.

Somewhere near the hot water heater the cold & hot water pipes are connected the cold water branches off, and the hot water branches into the heater & is the hot water side.

You can't say the hot & cold water lines are the same, so can tie them together anywhere I want to - you would have a mess of tepid water & no hot, no cold water....

Likewise, even tho the ground & neutral wire are bonded at one place (or should only be bonded at one place!) they are different from there on, and shouldn't be re-connected to each other later on. If you connect the hot & cold water lines together anywhere other than at the water heater, you end up failing the 2 sperate water lines and neither will work proper.

If that helps it make sense.

--->Paul

Yearssssssss ago some appliances like say stoves that had 240 volt heating elements and 120 volt clocks used a single wire for BOTH the Neutral and Equipment GroundING conductor.. NO MORE

Good advice below, here are my inputs so hopefully you can understand this in detail...

To run 240 volt you need the two Hot Phase Conductors (often black and red) L1 & L2 which are 240 volts PLUS THE SAFETY EQUIPMENT GROUNDING CONDUCTOR (often green or bare)

To run 120 volt you only need one Hot Phase Conductor (say L1),,,,The Neutral (often White),,,,,an Equipment GroundING conductor (Often Geeen or bare)

To run BOTH 120 and 240 volt, there needs to be 4 wires,,,,,,,2 Hots (L1 & L2 Black & Red), 1 Neutral (White), 1 Safety Equipment Ground (Green or bare)

On a typical 120/240 Volt Single Phase 3 Wire home distribution system its 240 volts Line to Line but only 1/2 that or 120 volts from EITHER phase wire to Neutral

DO NOT USE THE SAFETY EQUIPMENT GROUNDING CONDUCTOR TO CARRY NORMAL NEUTRAL RETURN CURRENT,,,,,,,,USE THE NEUTRAL (a groundED) conductor for that. The Safety Equipment GroundING conductor is to carry FAULT CURRNT ONLY

The Neutral (groundED conductor) and Equipment groundING conductor are bonded ONLY at the main service entrance panel NOT MORE DOWNSTREAM

The thing is since BOTH the Neutral and Equipment GroundING conductor are bonded at the main panel an appliance will work if those got substituted or used for each other etc BUT THAT CAN CREAT A DANGER AND IS NOTTTTTTTTTTTTTTT ALLOWED

Hope this helps, over on Johnnypopper a couple years ago I wrote a long article trying to explain all this, I will have to find it and post here sometime

Keep safe, best wishes n God Bless

John T Toooo Longggggggg retired EE and rusty on the latest NEC

Typically the safety Equipment Grounding Conductor (often green or bare) bonds to the outer metallic frame of a machine......

However, non current carrying devices such as the metallic junction box you mentioned also needs a bond to the equipment grounding conductor as does metallic conduit etc.

If youre running cords or romex etc to appliances each will have its own equipment ground but if youre running branch circuits via conduit it may be possible to use a single common equipment grounding conductor.

For an explanation of Grounds and Neutrals see my post above.....YES they are bonded at the main panel........YES an appilance can work if one or the other is used BUT DO NOTTTTTTTT DO THAT ITS A SAFETY HAZARD AND NEC VIOLATION

John T Its been yearsssssss sionce I was a secondary power distribution design engineer and Im rusty on latest code so trust someone with more current knowledge then myself if theres a NEC conflict i.e. No warrnty lol Hire an electrician

I worked in factory maintenance and over the years I found at least three different metal work benches sitting there at 120 volts potential. Usually it was caused by the wiring at the attached fluorescent lights. Either the ground wire was not originally connected or over time as things get bumped and moved around it would no longer be grounded and then when the hot wire touches the metal somewhere the bench would become hot. It is funny that more people don't get zapped.

Paul, I like your explanation of neutral/ground problems, but it makes me realize that every farm in our neighborhood is probably in violation of the current NEC. Our place is a good example of the bad. Our REA line comes in to a central pole, thru the meter (ground rod below meter) and branches out to three seperate buildings via three conductor cable. The closest building is about 50 ft, and the farthest about 150 ft and across the road from the meter pole. Each of the three buildings have a common ordinary breaker box with the ground/neutral buss bar(s) connected to a ground rod. I recently looked in one of the breaker boxes, and couldn't see any way to isolate the ground buss from the neutral buss, short of disassembly and the use of a hacksaw. This installation is about 20? years old, and we hired one of the REA linemen to do the work on weekends. I remember this man being a "detailer", even to the point of adding a conduit clamp to avoid a couple inch too wide spacing. I guess to make it "right", I need to replace all of the three conductor building feeds with a three conductor plus ground. Probably should, but probably won't happen in the very near future.

Thanks again for a good explanation.

Paul

The old NEC allowed you to run 3 wires (2 Hots, Neutral for 120/240) to a remote outbuilding fed from the main panel HOWEVER youre now required to run 4 wires, 2 Hots, Neutral, Equipment Ground. The old systems are likely grandfathered in but if you install a new system then you have to run the 4 wires

Hope this helps

John T

This was a good thread to read, people actually explaining, asking, and learning.

GREAT

Thanks for all the input. I will add an additional grounding (green) wire and connect it at both machines. The white (neutral) will now just serve the 120 volt buffer.