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Old 01-08-2012, 05:14 AM   #151
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Need to know if my grounds and neutrals are connected right


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I don't know if you all have convinced the OP yet, but I for one greatly appreciate this conversation. It has really helped me understand why the ground and neutral need to be isolated in a sub-panel. Thank-you all!

Dan
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You know what...if somebody learns something from all of this then it's worth it. Glad we could help you.
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Old 01-08-2012, 05:20 AM   #152
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Need to know if my grounds and neutrals are connected right


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And one showing why you cannot run other metallic paths to the detached building when using a 3 wire feeder.
Thanks for taking the time to draw it out Stubbie. I for one learn much easier with pictures and drawings vs. written words.
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Old 01-08-2012, 05:38 AM   #153
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Need to know if my grounds and neutrals are connected right


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There are 200 amp meter sockets that have provisions (lugs) on the load terminals for 100 amp sub-feeds. I'm not sure what the situation was where J.V. mentioned this, but normally these sub-feeds are permitted on rural agricultural properties.

The code reference is 230.40 exception 3
I have a similar situation with my rural property which is what brought me to this forum but I didn't know about this option. Looks like I need to study up on it. Can this be done to feed multiple buildings and would all buildings have the neutrals bonded to the equipment grounds and ground rods? I would be just as happy to run 4 conductors but this may be another option for me.

I'm going to start a new thread with some diagrams. Maybe I can get someone to answer me this time.
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Old 01-08-2012, 08:50 AM   #154
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Need to know if my grounds and neutrals are connected right


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Originally Posted by Terabitdan View Post
I don't know if you all have convinced the OP yet, but I for one greatly appreciate this conversation. It has really helped me understand why the ground and neutral need to be isolated in a sub-panel. Thank-you all!

Dan
I agree. I've learned more about grounding/bonding on this thread than dozens of others, and you guys have been really civil about the argument. I've read through some threads where some get into virtual fist fights over who is right and wrong.

This has been good

David
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Old 01-08-2012, 10:00 AM   #155
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Need to know if my grounds and neutrals are connected right


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McSteve:

If the grounding rod exists primarily to protect the wiring and structure from lightning, and other high-voltage events. Where does the so called circuit ground come from? The circuit ground is not provided by the power company, two hot and a neutral. Unless I am missing something, please explain.
I'd like that explained too. I've found numerous diagrams on the internet that show two buildings with power ran to them. Only 3 wires ran between then they show the universal sign that both buildings go to ground, signifying that ground is universal between buildings... so if building 1 is grounded and building 2 is grounded, the ground in building 1 should be the same ground in building 2...

Here's the first link I've found when googling... not me just skipping to the first one that proved my point...

http://www.diychatroom.com/attachmen...r-detached.jpg

There was one other person in this forum thread that said it was OK to run only 2 hots and one neutral as long as no other metallic elements ran between the barn and the house. So maybe that's why it was safe until 2008 codes? Before 2008, running other circuits, like computer networks and phone networks weren't common place to run to a detached building? Right now the only "metallic elements" I have running from my house to my barn is the 2 hots and one neutral.

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Old 01-08-2012, 10:08 AM   #156
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Need to know if my grounds and neutrals are connected right


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I'd like that explained too. I've found numerous diagrams on the internet that show two buildings with power ran to them. Only 3 wires ran between then they show the universal sign that both buildings go to ground, signifying that ground is universal between buildings... so if building 1 is grounded and building 2 is grounded, the ground in building 1 should be the same ground in building 2...

Here's the first link I've found when googling... not me just skipping to the first one that proved my point...

http://www.diychatroom.com/attachmen...r-detached.jpg

There was one other person in this forum thread that said it was OK to run only 2 hots and one neutral as long as no other metallic elements ran between the barn and the house. So maybe that's why it was safe until 2008 codes? Before 2008, running other circuits, like computer networks and phone networks weren't common place to run to a detached building? Right now the only "metallic elements" I have running from my house to my barn is the 2 hots and one neutral.
Why in the he.. do you keep begging for justification on this site? Do what you will and be done with it. The experienced people here are not going to give you peace of mind.
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Old 01-08-2012, 10:09 AM   #157
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Need to know if my grounds and neutrals are connected right


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There was one other person in this forum thread that said it was OK to run only 2 hots and one neutral as long as no other metallic elements ran between the barn and the house. So maybe that's why it was safe until 2008 codes? Before 2008, running other circuits, like computer networks and phone networks weren't common place to run to a detached building? Right now the only "metallic elements" I have running from my house to my barn is the 2 hots and one neutral.


And only 40 or 50 that said otherwise....but what do we know......


EDIT: So someone doesn't say I'm being "short", I'll expand....

That WAS code, prior to 2008. It has nothing to do with your electronic equipment. The NEC could care less of you fry your laptop...they care about you staying ALIVE.

New safety risks are found...codes adjust to suit.

What more can be said.....do what you want.

Last edited by jproffer; 01-08-2012 at 10:14 AM.
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Old 01-08-2012, 10:27 AM   #158
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Need to know if my grounds and neutrals are connected right


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And only 40 or 50 that said otherwise....but what do we know......


EDIT: So someone doesn't say I'm being "short", I'll expand....

That WAS code, prior to 2008. It has nothing to do with your electronic equipment. The NEC could care less of you fry your laptop...they care about you staying ALIVE.

New safety risks are found...codes adjust to suit.

What more can be said.....do what you want.
You didn't understand what I was saying and what the other person was saying.... I know safety code doesn't care if I "fry my laptop." Just before 2008, it wasn't common place to run other circuits between buildings, so they didn't write a rule for it. With 2008 code, they figured out a lot more people were running other circuits between their buildings other than just electric which adds "another metallic element" between my house and my barn which excessive voltage could stray across instead of the ground bar at my barn. And because of this, they made it mandatory to run a separate ground between the house and the barn.
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Old 01-08-2012, 10:32 AM   #159
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Need to know if my grounds and neutrals are connected right


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Originally Posted by dorlow View Post
You didn't understand what I was saying and what the other person was saying.... I know safety code doesn't care if I "fry my laptop." Just before 2008, it wasn't common place to run other circuits between buildings, so they didn't write a rule for it. With 2008 code, they figured out a lot more people were running other circuits between their buildings other than just electric which adds "another metallic element" between my house and my barn which excessive voltage could stray across instead of the ground bar at my barn. And because of this, they made it mandatory to run a separate ground between the house and the barn.
Oh................well OK then

You are right........the rest of us are wrong.......do it your way.






















BTW, If you don't see the sarcasm there, then you have bigger problems than a poorly installed sub-panel.
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Old 01-08-2012, 10:34 AM   #160
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Need to know if my grounds and neutrals are connected right


now you've made me go back on my word when I said I was done with this......


so now, I'm done with this.....again.................for now
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Old 01-08-2012, 10:37 AM   #161
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Need to know if my grounds and neutrals are connected right


Basically, the changes over time for grounding paths in the NEC are about probabilities and the correct determination of those based on empirical data right?

Let's say this barn has a bonded panel with a three-wire feeder. As long as the neutral path to the transformer is good then there's no problems.

It's about where that neutral path goes: subpanel, service disconnect, service drop, that increases the opportunity for an upstream issue creating a hazard in the barn. Back in the 30's, who cared? There was no empirical evidence for the danger. Then people started dieing in barns. Ok, the bonded panel in the barn needed to be directly connected to the service disconnect which reduced the number of places where that path back to the transformer could have "issues". Made things safer but by 2005 there was enough empirical data to show that even this was dangerous; if the single neutral path to the transformer was disrupted anywhere along the path to the barn, things got deadly in the barn again. So the 4-wire edict came into play. Now there are 2 separate return paths maintained all the way to the service drop. Much less of a chance to make one's body the path of least resistance. Still not zero though, so we have first GFCI and now AFCI requirements which are essentially an admission that there's always a chance that your body will make the best grounding path...

How close am I?

edit: I'm reminded of a time when I was a kid, playing in a barn and we found an old electric motor. I plugged that sucker into an outlet (one hand holding motor, the other holding plug) and got the pejeebees shocked out of me. Why? The metal case was energized due to a fault in the motor or God knows where else, and there was not a ground path (where all appliance metal cases now connect) back to the transformer. This was a two wire motor plugged into a two prong outlet. This was back int the 60s'... Barns were pretty dangerous places back then...

Just a quick nod to your "retro" barn wiring plans dorlow! You're making a barn that is just like the barns of old...

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Old 01-08-2012, 11:17 AM   #162
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Need to know if my grounds and neutrals are connected right


It used to be ok to run knob and tube wire also!
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Old 01-08-2012, 01:10 PM   #163
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Need to know if my grounds and neutrals are connected right


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...so if building 1 is grounded and building 2 is grounded, the ground in building 1 should be the same ground in building 2...
Sort of and also not at all!

The ground connection on an outlet which may go to the metal frame on an appliance like a washing machine does TWO things...

1. It is a lower resistance (measured in ohms) "path to ground" than your body is. Or in other words held at "ground potential" by that ground rod.

2. It is a low resistance (measured in ohms) path to neutral via the bond to neutral at the main panel. This will cause the circuit breaker to trip should an electrical malfunction occur which energizes the metal frame (hot wire short to metal frame).

So the questions are...

What is the resistance in ohms between two standard ground rods spaced 100 feet apart?

Is that resistance the *same* as with a large gauge ground wire connecting the two ground rods?

What is the resistance, measured in ohms, of your body measured from a hand to a foot?

Google the following words...

how to use an ohmmeter

ground resistance testing

Bottom Line: Case History of an Electrical Ground Failure - Loss of a Neutral Connection in an Electrical Sub Panel Badly Shocks a Homeowner...
http://inspectapedia.com/electric/El...utral_Lost.htm
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Old 01-08-2012, 01:22 PM   #164
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Need to know if my grounds and neutrals are connected right


From the following link...

["For many years, the street lighting and traffic signaling industries used ground rods, without an effective fault current path, to ground metal parts of an electrical system. Electricians thought these installations were safe because “electricity takes the least resistive path, and it bypasses high resistive paths.” Unfortunately, such thinking resulted in several deaths."]

The Path of Least Resistance...
http://ecmweb.com/mag/electric_path_least_resistance/

More...

Resistance...
http://en.wikipedia.org/wiki/Electri...nd_conductance

Ohm...
http://en.wikipedia.org/wiki/Ohm
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Old 01-08-2012, 09:27 PM   #165
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Need to know if my grounds and neutrals are connected right


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Here's the first link I've found when googling... not me just skipping to the first one that proved my point...

http://www.diychatroom.com/attachmen...r-detached.jpg

There was one other person in this forum thread that said it was OK to run only 2 hots and one neutral as long as no other metallic elements ran between the barn and the house. So maybe that's why it was safe until 2008 codes?
That person would be me ... and the drawing in the link you posted is also mine.

But I did not say it was ok in your situation. What I said was if your electrical authority in your jurisdiction was still enforcing 2005 or earlier you might be able to run a 3 wire feeder. You said you don't have any metallic paths existing so that helps but you need to make sure your building inspection authority does not have an amendment saying otherwise. There are states that have made a 4 wire feeder mandatory due to safety concerns long before the NEC required such.

So you might be ok with what you did but a 4 wire feeder is much better for safety and design over a 3 wire feeder... And ... you were required to run a 4 wire feeder because you are running it from a sub-panel not the service equipment. Unless you take the initiative to find out you will never know if you are code compliant or not.

Much of your problem is you are very confused about the earth grounding ( ground rods) and equipment grounding ( wires and bonded metal ).

Earth grounding is referred to as your grounding electrode system (GES) and the bare and green green wires in your branch circuits are the Equipment Ground System.

They serve two entirely different purposes ... the GES protects property and equipment against high voltage events like lightning strikes and utility power surges. The EGS provides for human safety against low voltage ground faults and protects against shock and electrocution. So lets take a look at the differences..understanding that under 600 volts is considered low ac voltage and I don't think I need to tell you what lightning is ...

The EGS is for human safety to keep you from getting electrocuted in the event of a ground fault. To understand this you first need to understand what is needed for an electrical circuit to function properly. So lets look at a diagram for starters that I have attached to this post.

1st Diagram is attached below .. I will continue explaining with more diagrams if you or anyone else would like to continue this discussion but I will stop with this post if there is no interest ...

It is important that you understand that current in any residential system seeks a return to the source transformer and it will take all paths provided intentionally or otherwise to get there in order to complete the circuit. Current also shows preference to paths of low impedance/resistance and will take those paths in greater proportion. With that understanding we construct only one low impedance path for current to return to the source in order to prevent objectionable current showing up in places where it is unexpected and dangerous.

Lastly the grounded legs (aka neutrals or white wires) of 120 volt branch circuits are current carrying wires just like hot wires and are just as likely to shock you ... never confuse them as the same as equipment ground wires which are only meant to carry current briefly during a ground fault event until the breaker opens on overcurrent and de-energizes the circuit.

Notice in the diagram the alternating current (red dots) begins and returns to the source (transformer). Notice also that I show no current going to earth. The reason is that the resistance of dirt (as compared to low resistance/impedance of wires) is so high that current will not 'choose' to go to earth because we have intentionally constructed a low resistance/impedance path back to the transformer over ungrounded and grounded conductors with the service neutral being a very key player for a couple reasons. It is the only low impedance/resistance path from the service equipment to the transformer center tap. Without that link to complete the circuit your electrical system could not operate anything needing 120 volts like lights and appliances...and...your circuit breakers would not be able to trip on ground fault.

As long as that stays in place and remains unbroken 99.9999% of all neutral current will use it to return the source. This is a result of a secondary low voltage source transformer serving the house at 240/120 volts over 3 wires (H-H-N).

As long as this circuit is intact and there are no ground faults .. all is well. Remember you do not need the connection to earth as shown by the ground rods for your electrical system to operate. These are present for property protection as mentioned earlier and to a small degree earthing helps stabilize voltages in the event of a lost service neutral.

Also you do not need the ground rods for circuit breakers to trip that is the purpose of the EGS not the GES.
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Need to know if my grounds and neutrals are connected right-120-volt-branch-circuit.jpg  

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