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I have a 50 amp subpanel in my barn. It appears the grounds and neutrals are on the same bus. My understanding is this was acceptable on a 3-wire subpanel until around 2008, when code changed to require a 4-wire.

Question is, what's involved to repair/upgrade? Separating them, and running a separate ground all the way to the main/service panel? Can i leave it as is? Can i seperate and just install an additional ground at the barn? Original install was probably in the 1990s, before i owned the property.

I have 220v working fine in the barn already. Looking to add a new 220v compressor and want to make sure wiring is in good shape. I'm ok with having an electrician do the work, just hoping to get independent opinion on what's required.

Thank you for any ideas or info.
 

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A 3 wire feed to a detached structure with no metallic path between buildings was allowed a before the 2008 NEC. It is allowed to remain.

The panel would require a grounding system. The neutral to ground bond needs to be installed.
 
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As others have said, you are not obligated to change it since it is grandfathered in and met code at that time.
A grounding rod and a ground bond will take care of any issues.
 

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LOL no it won't! They changed the code for a reason.

What they're telling you is don't separate neutral and ground unless you are able to run a ground WIRE back to the main panel.

A lof of people say "what's the difference, isn't the ground rod and ground wire doing the same job? No. Dirt is a terrible conductor, that's why we bother to mine copper instead of just wrapping dirt in insulation.

The ground rods deal with lightning and ESD. The ground wire deal with overload and short circuit trips, it assures enough current can flow to get a breaker trip, instead of just sitting there glowing cherry red.

The separate neutral and ground are there because neutral wires break, and if there isn't a separate ground, the outbuilding's grounds will float many volts above neutral and float the soil in the vicinity.
 

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I have a 50 amp subpanel in my barn. It appears the grounds and neutrals are on the same bus. My understanding is this was acceptable on a 3-wire subpanel until around 2008, when code changed to require a 4-wire.

Question is, what's involved to repair/upgrade? Separating them, and running a separate ground all the way to the main/service panel? Can i leave it as is? Can i seperate and just install an additional ground at the barn? Original install was probably in the 1990s, before i owned the property.

I have 220v working fine in the barn already. Looking to add a new 220v compressor and want to make sure wiring is in good shape. I'm ok with having an electrician do the work, just hoping to get independent opinion on what's required.

Thank you for any ideas or info.
It should be wired exactly the same as a new service. You have 2 energized conductors and one Grounded Current Carrying Conductor (GCCC), commonly called the neutral conductor even though that is not always true, in the feed line from the Service Equipment's location.
In your feeder supplied panel at the barn you need to connect the 2 energized conductors to the main breaker. If the Building Disconnecting Means enclosure at the barn has no main breaker and contains more than 6 individual breakers you must install a 2 pole breaker with a tie down kit that prevents it from being removed from the busbars without tools. If it were removed while the feeder were energized the breaker's busbar grips would still be energized and exposed to accidental contact. That held in place breaker becomes the Barn's Building Disconnecting Means. The 2 energized conductors are terminated to that breakers terminals were loads are normally connected. That single breaker will cut off all electric power to the barn with a single throw of your hand.
The GCCC (Neutral) connects to the multi terminal busbar that was built into the panel at the factory. That is commonly called the Neutral busbar.
The "Neutral" busbar is bonded to the panel's cabinet in all cases were there is no Equipment Grounding Conductor run with the feeder conductors. Cabinet is the proper name for a panel board's enclosure in sizes of 400 amperes and less.
A grounding electrode array consisting of a minimum of one driven rod with a resistance to earth of 25 OHMS or less or 2 driven rods at least 6 feet apart is built. [Best practice is to separate the rods by twice the length of the longest rod. That would make the separation between 2 rods 8 foot in length 16 feet.] The US NEC only requires 6 feet of separation and no one can make you do more but 2 driven rods only 6 feet apart is some steel pretending to be grounding electrodes. Early on in my career I bought a used 4 pole, fall of potential, Grounding System Impedance Tester. I later bought a used clamp on ground impedance tester. I tested the grounding electrodes I installed as often as I was able sometimes staying an extra 1/2 hour on the site to do so. I only saw the 2 rods at 6 feet apart come under 25 Ohms a couple of times. They were usually above 50 Ohms and sometimes over 100 ohms. I never had a concrete encase electrode come in above 25 ohms. Genuine Ufer Grounds with all of the 1/2 inch steel rods in the footer and floor of a "slab on grade" bottom floor with no insulation nor vapor barrier under the concrete were often so low on the impedance meter that it was difficult to get any impedance reading at all. Sometimes I would put a 25 ohm resister in the current line of the fall of potential ground impedance tester just to be sure that the equipment was working before I was able to believe such low readings.
The other Grounding Electrode that performs rather well is a Ground Ring. That is 20 or more feet of bare #2AWG copper wire encircling the building at a minimum depth of 30 inches. The 20 foot minimum is to deal with pump houses, guard shacks, fueling sheds, and other small foot print buildings that would not achieve adequate performance if the loop were just long enough to tightly circle the building.
The National Institutes of Standards and Technology (NIST) has done extensive work on the effectiveness of various Grounding Electrodes. What they recommend for a fully effective grounding electrode system for a residential building is a 20 foot trench with a depth of 30 inches. 2 rod electrodes are driven through the bottom of the trench at each end and a bare number 2 copper conductor is connected to the furthest rod, the closest rod to the building, and on to the Building Disconnecting Means of the Feeder supplied structure were it is terminated on the neutral busbar. It is not a code requirement in any sense but it nearly always has a low impedance connection to the earth. It is also the easiest effective electrode to install.

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Tom Horne
 

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Everyone is fine with this happening to a dwelling, but heaven forbid it happen to a barn.
The difference between the separation of the legs of livestock and humans, that fact that livestock often stand for prolonged periods in there own conductive waste, and the effects of any deterioration in the stocks health on the rancher's livelihood would all tend to explain that. It is now a confirmed fact that livestock, especially dairy cows, are much more vulnerable to step potential injuries than 2 legged humans are.

Tom Horne
 

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But more basically, the presence of almost any step potential really freaks out the animals. And that causes stress and failure to thrive, and now you're looking at vet bills.

And no, it's not OK for homes either.

As always, being stupid with electricity doesn't pay.
 

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I have a 50 amp subpanel in my barn. It appears the grounds and neutrals are on the same bus. My understanding is this was acceptable on a 3-wire subpanel until around 2008, when code changed to require a 4-wire.
No, actually, it was NOT. What used to be permitted is not running a separate grounding conductor between the two buildings. If you have a subpanel in the barn, it was SUPPOSED to have grounds separated and going to the barn's own grounding system (e.g., rods) and the neutrals going back to the feeding structure.

What you have is dangerously unsafe.
1. Install a grounding system if you don't have one.
2. Install a grounding bar (if required by the design of the panel) and unbond the neutral bars (if possible).
3. Make sure the grounds and neutrals go to the right bars.
4. Make sure the grounding electrode is connected to the ground bar.
 

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No, actually, it was NOT. What used to be permitted is not running a separate grounding conductor between the two buildings. If you have a subpanel in the barn, it was SUPPOSED to have grounds separated and going to the barn's own grounding system (e.g., rods) and the neutrals going back to the feeding structure.

What you have is dangerously unsafe.
1. Install a grounding system if you don't have one.
2. Install a grounding bar (if required by the design of the panel) and unbond the neutral bars (if possible).
3. Make sure the grounds and neutrals go to the right bars.
4. Make sure the grounding electrode is connected to the ground bar.
Totally wrong! Without the neutral ground bond a ground fault will not pull enough amps to trip a breaker.

Example: Ground resistance 20 ohms. A best case.

120/20= 6 amps

Sent from my SM-T500 using Tapatalk
 

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No, actually, it was NOT. What used to be permitted is not running a separate grounding conductor between the two buildings. If you have a subpanel in the barn, it was SUPPOSED to have grounds separated and going to the barn's own grounding system (e.g., rods) and the neutrals going back to the feeding structure.

What you have is dangerously unsafe.
1. Install a grounding system if you don't have one.
2. Install a grounding bar (if required by the design of the panel) and unbond the neutral bars (if possible).
3. Make sure the grounds and neutrals go to the right bars.
4. Make sure the grounding electrode is connected to the ground bar.
flyingron
Get your code history straight before you start typing. Outbuildings were permitted to be wired exactly the same as Service Equipment just as if it was receiving it's supply from the electric utility. The number of conductors in the supply to each building, grounding electrode system required, and limiting number of disconnects permitted at each building to 6 were all applications of the rules for Service Equipment.

The earliest version of this practice did not have service equipment at the "Meter Poles"; which were utility owned. The Utility would use current transformers around the conductors from their transformer at the last point before they were separated into Service Drops. From the "Meter Pole" the utility conductors would drop to the individual buildings' Service Equipment. The demarcation point between the utility conductors and the service equipment was at the end of the service drops were the utilities conductors were spliced to the Service Entry Conductors of EACH BUILDING.

The next iteration of supplies to separate buildings were also run as overhead open wiring on insulators which served as a Feeder Drop from the customer owned "Yard Pole" to the individual buildings. This was a cost shedding maneuver by the investor owned (stock) electrical utilities. It was done to change the responsibility for the construction and maintenance of the conductors to the individual buildings to the consumer instead of the stock electrical utilities. The service demarcation point for those services was at the splices between the utility owned span from the last utility owned pole to the customers' single set of Service Entry Conductors going down the utility side of the customer owned "Yard Pole" were it terminated in the Service Equipment mounted on the pole itself or on a mounting board immediately adjacent to the pole. All of the costs for the rest of the supply conductors between the utility span and the individual buildings was born by the customer. Since even the existing customers were required to have a single set of Service Equipment the same drop wires which had been utility owned now became feeders and therefore customer property. Nothing had changed about the actual wiring serving the individual buildings except their ownership. All that did change was that there was now a Set of Service Equipment which controlled the power to all of the buildings served. Al that was done with the acquiescence of the various States Utility Regulatory bodies.

That history is fact! It is easily researched to confirm it. Literally millions of feeders supplying separate buildings were built exactly that way. They were fully compliant with the US NEC then and they are fully compliant with the NEC now. There is no pile of bodies across the country's suburban and rural landscape from this practice.

The change to the present requirements was made in response to the development of other kinds of wire provided utilities, such as cable television and inter-building telephone extensions. Once parallel conductive pathways between the separate buildings began to become commonplace problems began to arise from the voltage drop in feeder conductors with the addition of more and more load to the wiring systems of separate buildings. Since these new wire delivered services often had one of their conductors grounded at both ends, to the same grounding electrode system, the shields of coaxial cables and the grounded conductor of Ground Start telephone lines, as examples, would carry the normal neutral currents of the building, in proportion to each conductors impedance, to the Electrical Service's Main Bonding Jumper and back to the source of the current at a utility pole mounted transformer on the last utility owned pole. It was the flow of regular neutral current over these parallel pathways that caused problems to both the power utilities' equipment and the outside plant of the other conductive pathway service providers. these problems were exacerbated by the substitution of plastic piping for water lines between buildings. The costs of such damages rose with the continuing market expansion of these other wire carried services. In the end it was this increasing damage to all of the service provider's outside plant that precipitated the change. The National Fire Protection Association's Code Making Panels changed the code to prevent the steady increase in losses from causing intervention by the State Public Utility regulatory bodies with a solution of their devising.

Tom Horne
 

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If this is in the same structure, there should be grounds going back to the main panel and no ground bond between neutral and ground and grounds and neutrals should land on their respective bus.

If this is in a different structure, you need to see if there is a ground going back to the feeding structure. If there is, you don't want the ground to neutral bond and again keep the grounds and neutrals separate.

If this is a different structure, and subject to whatever grandfathering may historically be in place, you may not need the ground running back to the feeder. In this case you want the neutral and ground bonded here (you can use the same bus bars or not).

Any structure with more than a single (possibly multiwire) branch circuit connected to it needs a grounding electrode system (e.g. rods). The thing supplying a subpanel is not a single branch circuit, it's a feeder.
 

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If this is in the same structure, there should be grounds going back to the main panel and no ground bond between neutral and ground and grounds and neutrals should land on their respective bus.

If this is in a different structure, you need to see if there is a ground going back to the feeding structure. If there is, you don't want the ground to neutral bond and again keep the grounds and neutrals separate.

If this is a different structure, and subject to whatever grandfathering may historically be in place, you may not need the ground running back to the feeder. In this case you want the neutral and ground bonded here (you can use the same bus bars or not).

Any structure with more than a single (possibly multiwire) branch circuit connected to it needs a grounding electrode system (e.g. rods). The thing supplying a subpanel is not a single branch circuit, it's a feeder.
just when i understand , ..........There is more if's its this way or this way, Mine was done befoe 1980 . Only 3 wires run to sub panel from 200 amp main to a 100 amp breaker in sub panel. SO should grounds and neutrals be bonded on same wire returning back to Main box 50' away? and if so should bonding screw be installed in sub box too?
 
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