Calling JohnT and BD!!! Sub panel issue!!!

After reading all of the posts about sub panels and the grounding issues I took some time today to check the panels around the farm. It was time to clean them out anyway. I usually take the covers off once each year and use compressed air to blow all the crap out of them.

All of the sub panels but one have ground rods right by them. All within 3-4 feet of the panel. So I have the sub panels hooked up just like the main service box is hooked. Meaning the neutral and bare grounds are hooked to the same bar inside. There is a bare ground hooked to the bar an out to a copper ground stake at all the panels but one. At the supply end at the main service box they are hooked the same way.

My thinking is that with an earth ground right there that there is no way to get the ground loop issues that you are talking about if you hook the neutral and ground on a sub panel that does not have an earth ground going to a stake.

Now the one that is different. First off it has been installed like it is for 28 years. LOL No issues YET. It is a 100 amp Main service box I took out of a house we remodeled and put in a 200 amp service. Since it was a real good Square D box that had eight separate breakers I used it when I wired the cattle shed. This box has no other way but for the neutral and earth ground to hooked to the same bar. The trouble with this box is its location. It sets on the shed right where there is a bluff rock under it. The concrete is only a few inches thick in places right where it is at. So there is zero way to drive a ground rod.

Now why it maybe never caused any issues. I had some hogs killed many years ago when an electric heater shorted out and electrocuted about 10 sows a week before they where to pig. Just about got me when I went to see what had happened. The shorted out heater had the entire fence electrified. Since that happened I have an earth ground at every waterer that has an electric heater in it. Not just hooked to the water line I mean a 10 foot copper ground rod. So this box had eight waterers on it that have earth ground stakes. All the bare grounds are hooked to these ground stakes. The neutrals are run back to the box and hooked like a main service would be. The bare grounds are hooked to the ground stake at the waterers and to the ground bar in the sub panel box. Would all of these be a replacement for a normal ground stake that would be at the sub panel???

Kind of got me worried thinking about it. There are over 700 fat cattle in that shed and yards. That is some serious money to have an electrical issue cause a problem. Before I came to the house I shut that sub panel off at the main service until I get an answer that relieves my concerns. My electrician friend is on vacation this week so I can't reach him until Monday. He has looked at this box and never said anything about the grounds/neutral bar issue.

So am I worrying about nothing or do I need to replace the box with one that has a separate ground and neutral bar in it???

I have seen those separate ground bars you just fasten with some screws in the box over at the side of everything. I guess I could install one of these and move all the earth grounds to it and separate the neutrals at the box. It would be some work because some of the wires would not be long enought to reach a different bar.

So what should I be doing???

Not the guys you are looking for but here goes anyway. It is only a subpanel if it feeds from an overcurrent device. In the State of Nebraska they say that the farm loop with a generator transfer switch or just plain disconnect on the meter pole is not the first disconnecting means, just a convenience disconnect. This means that any shed or house that feeds from the meter pole is a separate service, not a sub panel, unless there are 2 panels in that building. Therefore you do not have to worry about separating the grounds and neutrals in the panels.

In regards to your grounding issue at the one shed on rock, by code you are allowed to use a grounding plate. This is just as it sounds, a metal plate of the right size(someone else chime in here with the size) and has to be completely buried. I am not too familiar with this type of grounding since rocks here are awfully scarce. If you grounded the reinforcing wire/rebar in the concrete it would help also. I would guess with all the ground rods that you have driven by the waters' it is grounded plenty good. Just FYI, the code book says to have any concrete and metal parts(gates/fences/etc) all bonded together so that if one is electrically charged there is not a really good ground by touching the other, the technical name is equipotential plane. Kinda like getting shocked every time you touch the range and the sink, the range has a little short to the ungrounded frame and when you touch the metal grounded sink you make the path.

Hope this helps a little. Glad you are trying to do it safe.

Hi JD, hope you don't mind me chiming in.

Sorry about those hogs lost :-(

For a proper safety ground, you need a separate bare run in the bundle from the main panel to all other sub-panels passing through each. The grounding rod can stay attached to the bare ground at the sub-panels, good for lightning strikes. And yes the bare ground sizing needs to be big enough to carry a short all the way back to the main neutral bar.

The main thing to remember is "never let the bare ground carry any load current whatsoever." Safety ground is meant to provide a virgin path back to neutral at the mains in order to quickly trip the breaker for any short circuit to equipment ground.

The problem with tying the ground to the neutral at sub-panels is that the ground now becomes part of the neutral carrying load current and eliminates the pure safety ground.

Amen,

Greg

Another thing is that what I said pertains to a single building with a mains and other sub-panels.

I personally run separate grounds to the storage shed and pole shed from the house sub-panel that also has the neutral isolated from the box equipment ground.

I have over-kill (oxymoron) for my safety ground.

That being said it sounds like you may not have a separate ground run which causes you to treat each building as a main where you have no choice but to use the neutral bar for safety ground at that location.

Greg

I have four wires ran to each sub-panel. The two hots, insulated neutral and a separate Green/bare ground.

The neutral and grounds are hooked to the same bar in the boxes. At least all the sub panel boxes outside are that way. There is a sub panel in the up stairs that is a newer box. It has the isolated bars so the neutrals and grounds are separate. I also ran four wires to it.

I suggest you install GFCI breakers on any circuits that power waterers or other equipment your livestock will contact.

JD, First of all, I commend you for taking the time to ask hard very legimitate questions and trying to GET THIS RIGHT, safe and NEC proper as most of the untrained but still "know it all" Billy Bobs of the world dont care as long as it works and pooh pooh the NEC and trained experienced professional electricians and engineers.......Also, unlike some, you ask advice and follow up questions AND ACTUALLY READ AND LISTEN to responses. As I always say, however, dont just take my word for it, consult the NEC and more current professionals AS IM LONG RETIRED AND RUSTY. Still, I give what I recall as the best professional (albeit rusty) advice and try my best to help protect life and property. Im here to try n help NOT feud lol answers

I CAN TELL YOU WHERE YOU WENT WRONG but dont take offense as you're at least trying to GET IT RIGHT and are rightly concerend for your own as well as the buildings safety.....

You done good by running 4 wires (2 Hots, Neutral, Equipment Ground) to those out buildings

BUT AT THOSE PANELS YOU DO NOTTTTTTTTT I REPEAT DO NOTTTTTTTTTTTTT BOND NEUTRAL BUSS TO EQUIPMENT GROUND BUSS, THEY ARE TO REMAIN SEPARATE AND ISOLATED. When you bond them you defeated the whole purpose of running 4 instead of only three wires in the first place like was done days past !!!!!!!!!!!!!! Some panels suitable for use as Service Entrance have a tie bar to conenct Neutral and Ground busses when they are the main panel but the ability TO NOT ATTACH them when used as a sub,. Of course, some panels intended ONLY for mains have but one common buss where BOTH Neutrals and Grounds attach.

NOTE 1, I'm sure youre already aware the main service entranced Panel DOES BOND THE NEUTRAL BUSS TO THE EQUIPMENT GROUND BUSS but once more DO NOT DO THAT AT THE SUBS, those 2 busses are kept separate and electrically isolated.

NOTE 2, HOWEVER, as its a non current carrying metal enclosure, the sub panels case/frame DOES BOND TO THE EQUIPMENT GROUND BUSS REMEMBER there may be a screw into the frame to accomplish that

THE THEORY FOR THE ABOVE and why I think Im still right regardless of being NEC stale is.

1) THE EQUIPMENT GROUNDING CONDUCTORS ARE SUPPOSED TO ONLYYYYYYYYYYY CARRY FAULT CURRENT (via a dedicated low resistance fault current return path) so the breaker will trip fast and deenergize maybe a hot case you might touch.
IT CAN SAVE YOUR LIFE
2) The (insulated so you dont touch it) Neutral GrounDED Conductor is for ONLY carrying normal return current NOT fault current.
3) If you mix n match and substitute one for the other and the right set of wrong things (opens, shorts etc) happen an appliances outer metal case you touch becomes the same as the insulated (NOT supposed to touch) Neutral and your body could be in paralell with a live current carrier I DONT LIKE THE SOUND OF THAT DO YOU?????????????

EQUIPMENT GROUND IS NOTTTTTTTTT NEUTRAL
EQUIPMENT GROUND IS NOT SAME AS EARTH GROUND
THE NEUTRALS ARE EARTH GROUNDED FOR SURGE AND
LIGHTNING PROTECTION (Why engineers and
electricians call them GrounDED Conductors)


When you re bonded Neutral to Ground at your subs YOU HAVE NEUTRAL CURRENT FLOWING IN PARALELL WITH THE EQUIPMENT GROUND and are making them the same.....Thats very very WICKED and badddddddddddd lol

SHOCKING LIVESTOCK ISSUES

There are indeed NEC exceptions for ag buildings used to house livestock BUT IM NOT CURRENT ON ALL THAT but can tell you this.

When wires like hots and neutrals and grounds are ran close by, mutual magnetic inductive couling and the capacitor affect may well elevate voltge on the ground wire AT A VOLTAGE HIGHER THEN MOTHER EARTH at some location away from the panel, so when old bossys nose touches a metal waterer SHE FEELS A SHOCK. Therfore if theres a ground rod right at the waterer wired to the case/frame that brings the case voltage back down to the same as the waterer so no shock for old bossy......

HOWEVERRRRRRRRRRRRR those ground rods DO NOT and are NOT to be substituted for the required buildings electrical service GroundING Electrodes. Right at the buildings service entrance you need its own suitable GroundING Electrode DONT USE THE WATER GROUNDS FOR THAT

NOTE AND DISCLAIMER like I said Im rusty on the Ag livestock building exceptions but best I recall thats why they have an exception to the otherwise SINGLE POINT GROUNDING METHOD

If I had the exact answer to the ag shock problem you know Id tell you but I just dont have time today to read up on it sorry, but think the above theory is correct and why a ground rod at a waterer prevents shock and may be permitted even if it defeats otherwise single point grounding BUT I STILL KNOW THOSE ARE NOTTTTTTT FOR USE AS THE SERVICE GROUNDING ELECTRODE........

PS You mentioned a panel with ONLY ONE BUSS, those are intended ONLY for main service entrance use where Neutrals and Grounds all tie together NOT SUITABLE AS IS FOR A SUB. However if you can modify it so all the grounds (and case/frame) tie together and the Neutral Buss is insulated off the case/frame it can work.

WHAT TO DO????? See if you can isolate the Neutral Buss in the subs insulated off the case frames, but the case/frame still tie to Ground buss remember..........

WHEWWWWWWWWWWWWWWWWWWW youre working me JD but Im glad to help. You sure do help others here..

John T (NO warranty, dont take my word alone for this, Ive been wrong before lol, so if a professional can help out here let me know but please sight some NEC authority (NOT just Billy Bobs method) so I can read up on it)

Problem is in those very wet n dirty areas, nuisance tripping could be a problem. It only takes like 5 MA to trip them. Old Bossy gets shocked because the equipmet ground running in paralell with other wirs can elevate its potential higher then mother earth at that remote location, which is why as I best recall (NO Warranty) they can be earth grounded to take their potential back down same as local earth even though otherwise that violates single point grounding method. Not sure of this, its been years since I read up on those ag building exceptions

John T

Separate your grounds and neutrals in the sub panels. Make SURE the sub panel feeders are terminated correctly at the distribution point. Not sure what your sub panels are fed from? I assume a center pole maybe?

Your electrician probably didn't say anything because it has been that way, right or wrong. As a electrical contractor who does a lot of agricultural work, I always do things right on my work......but it is often a real struggle to get a farmer to change something that has been "working ok" for years, even if it is not right.

Most guys don't seem to want to spend much more than they have to on electric work. I understand that.

Example, often on service calls I will notice subpanels with no separate EGC, and the neutral and grounds landed on the same bar in the panel. I mention the issues with this, and what we need to do to fix it. Often, I get the response of it works, has always worked, why change it? (not fix, change, lol)

One guy even had 12 Holstein cows die while milking one night due to stray voltage.....and couldn't convince him why his silo service needed ground rods.....after the overhead service burnt up, and it burnt all the silo unloader wire up, and wire to the rotating bunk feeder up, searching for a path to ground......It found it somehow through the rebar in the concrete and the silo unloader. some guys just don't get it.

Separate your grounds and neutrals in your subs, a ground rod at the panel is not a bad thing. Make sure your main service is put together correctly also.....that will be just as important.

Great! You have the safety grounds run separate.

Now you have the ability to easily make the sub-panel ground attach only to the box ground bar for equipment ground.

All panels have the neutral bar isolated from the box, just like the hots are isolated from the box. The only difference is that the main panel ties the neutral bar to the box with a strap or a green screw.

Remove the bonding strap or green screw in the sub-panels.
Make sure the sub-panel neutral is connected to isolated neutral bar and the safety ground is connected to the box grounding bar alone.

And yes if you can afford the GFCI's at the waterers, then go ahead, but eehhhhh......

Amen again....

Greg

BTW you may have to get some grounding bars for sub-panels that do not have one. Not a big deal, i trust you can do it.

Always make sure the mains are off, NO SHORTCUTS or HASTY DECISIONS with 240 volts brother.

240 volts means serious business.
Be careful or get an electrician if you have butterflies about it.

Regards,

Greg

EXCELLENT,,,,,,When I was practicing I had a great relationship with my electrical contractors, we listened to and learned from each other, a two way relationship based on mutual respect, I learned from them and they learned from me......Of course, I was older and more experienced by then, NOT some punk pimpled wet behind the ears kid fresh out of engineering school, they kind they didnt like lol

Couple comments: "some guys just don't get it"

I agree, Ive fought that for over 15 years here AND THEY NEVER WILL lol

"a ground rod at the panel is not a bad thing"

When I practiced I specified a proper GroundING Electrode at EACH AND EVERY buildings electrical service entrance.

Fun chat, I think JD has the picture now, but I'm rusty on those ag building exceptions

Ol John T and all

As several others mentioned, a 4 wire system is a good thing, but neutrals and grounds should not be bonded at subpanels. Someone mentioned a grounding plate electrode in place of a rod, so I looked it up. It must be a conductive material (duh!) and must have a minimum surface area of 2 sq ft in contact with the gound. If made of steel it must be 1/4" thick. If made of non-ferrous metal it must be a minimum .006" however aluminum is not permitted. Here's the catch, it must be buried at least 30" deep to be code compliant, so if you have rock right at the surface it may not help! (all info paraphrased into english from NEC Article 250.52 "Grounding Electrodes"
John T also got me curious as to special ag building requirements, so I perused Article 547 just a little also. For the most part, the special ag requirements are what one would expect as far as protecting equipment and wiring from damage by livestock, corrosive environments, and water, but a couple of things popped out at me that I was previously unaware of. One is that any electrical system in a livestock area must be equipped with a "site-isolating device." By the NEC definition, a site-isolating device is just a disconnecting means (disconnect switch, main circuit breaker, pole-top knife switch with ground operated handle, etc) It struck me as odd because I don't recall the term "site isolating device" being used elsewhere in the code. If your cattle shed panel has a main breaker, I would say that qualifies. The second was a provision requiring equipment grounding conductors to be copper, and if installed underground it shall be insulated copper.
The third item that I noticed in Atricle 547 involves equipotential planes, which someone else also mentioned. Basically, in concrete floors, in all areas where "metalllic equipment is located that may become energized" a grounded grid must be placed in the concrete. I think a waterer with connected heater would qualify as one of these locations. This is simply a mat of rebar or conductive mesh that is placed below the concrete and bonded to all metal structures and connected to the electrical grounding system. The idea is to prevent the stove-to-sink type shock mentioned in another post. If you have ground rods driven at all waterers, that is definetely a good thing, but make sure that they are connected not only to the equipment grounding conductor, but to the case of the waterer as well.
As far as splitting your bonded neutral panel into an unbonded panel, you can buy ground bars at any hardware store. With all wires disconnected from the old neutral/ground bar, place an ohmmeter between the bar and the ground rod wire, as well as the bar and the panel case. If it is properly isolated, it should have an infinite resistance. Then you can reland all neutral conductors on the existing neutral bar and move all ground wires including the one coming in with the feeders to the new ground bar which gets bolted directly to the panel case. (there are often pretapped holes in the case for this purpose)
I know this got a little long, but hopefully it was helpful...
Work Safe!
Jess

Thanks for the ag building code research, the theory is about as I recall it, which is to bring the waterers etc. back down to the same potential as mother earth where old bossy is standing so shes not shocked...All those paralell runs with ground next to the hots with capacitance and inductance can elevate its potential AND A BIG METAL PLATE BURIED IN THE VICINITY is a good "equalizer"

Fun chat for some of us at least

John T

When you get a [in this case free ] new [or used and not abused] panel. and it has one bar [because it was someones main panel] you simply go to the supply house and get a Square D ground bar kit which will mount right into [possibly] pre drilled holes. Now you can terminate all those outerbuilding grounds into that and separate the neuts and grounds . Now your grounds are not current carrying . This is what they want --no current on the grounds. If you have alot of them and the counterman brings a small bar out ask for a larger one . There are many sizes and easy to instal. Sometimes I will set the bar then re loosen it off the panel place all the ground wires into it then re install it with the wires tucked neatly to the tight side of the panel.Inspectors will also accept the bar being mounted with self tapping sheet metal type screws if there is not pre-drilled Square D panel holes.When you do this changeover you need to have the panel off because some grounds and neuts will be under the same set screws and if there is a load on the circuit arcing [or maybe you get shocked. It is not a hard job unless the sloppiness now is a disaster. The add on ground bars kits are not expensive.It would be a good idea to correct this for the reasons given by others below.

What do you recommend on a farm such as mine with several sub panels, each fed with three wires, all buried cable a LONG way from the main panel? No animals. No trouble. Ground rods at all locations. Apparently code has changed since my installations. It appears all neutrals and grounds are hooked together in all panels.

I really should have read this better. Do what he said.[Samuels68] and nevermind on what I said . Haha OOPs. Ground bar yeah that what ya need .

I recommend you do NOTHING, thats the way the code was for yearsssssssssssssss, it was likely legal when installed and maybe Grandfathered in by your local authority??????? In those days for 120/240 volt single phase three wire you only ran 3 wires to the outbuilding, 2 Hots and Neutral, just the same as the utility ran the twisted triplex 3 wires to your home. Then the Neutral was wired to a suitable GroundING Electrode and Neutral and Ground busses (if it even had two) were tied together.

But do as you please, I wouldnt be too anxious to raise any red flags i.e. dont ask dont tell and keep under the radar. Sure as you ask some bureaucrat and bring it to his attention he may call the SWAT team and the EPA and OSHA and run out and shut you down lol

PS Im always preaching do it right and safe, but while I believe the new 4 wire system to be better, the old 3 wire arent any great hazard in my opinion provided correctly installed and good earth grounding BUT IF A NEW INSTALLATION GO WITH THE CORRECT MODERN 4 WIRE

My opinion only, your choice now

John T

As always, thank you John. Indeed, I see questions asked on here that make me wonder if the SWAT/EPA/OSHA/NSA/etc. isn't going to come after us freedom loving rednecks!
I'm not about to dig everything up. Short of adding a wire, by my limited understanding, there's nothing else to do.
I just wondered if there was something that could be done at the panels.

A thing [[oh oh I was thinking and drinking beer last night] I thought of. If there is a green screw in that neutral bar now you need to remove this screw[may not be green ] .It will go through the bar bonding the bar to the back box . That needs to be removed if you separtate grounds to their own bar. Probably was mentioned below but it dawned on me that you need to remove the bonding screw.