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Old 12-16-2008, 12:21 PM   #1
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Confused About Grounding?


I'm a bit confused about proper grounding? I have a 200amp service coming off the pole which is switched at the pole. There is no ground rod at the pole other than the one the power company put in coming down from the transformer.

From here I have 3 wires running into a building which is a steel pole barn combo riding arena/horse stall barn to a 100-amp service panel (in the riding arena section). It also has no ground rod.

From there I have 3 wires running to another service panel (in the horse stall section -- same steel building just goes off perpendicular to the riding arena) from a 100-amp breaker in the first service panel. The second service panel is also a 100-amp breaker panel.

My questions are:

1) Should each of the service panels (and the pole for that matter) have a ground rod?
2) Should the grounds and neutrals be tied together in each service panel?
3) Should they then be connected to the ground rods (if needed at each service panel)? or Should the grounds and neutrals be seperated and only the bare grounds connected to the grounding rod?

I've gotten conflicting reports from different sources. You guys seem to be the most knowledgeable from what I've read in other posts on this site.

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Old 12-16-2008, 12:49 PM   #2
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Confused About Grounding?


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Originally Posted by nprranch View Post
I'm a bit confused about proper grounding?
Don't feel bad. You are not the only one, including many electricians.


Quote:
My questions are:

1) Should each of the service panels (and the pole for that matter) have a ground rod?
Not necessarily. At the pole, the neutral was grounded by the utility ground. Since your building is steel, your ground there can probably be taken from the building steel itself, as this is a code requirement. No rods needed in that case.

Quote:
2) Should the grounds and neutrals be tied together in each service panel?
Only at your first means of disconnect. Since the "first" disconnect is at the utility, it probably belongs to them and doesn't count. In your first panel, you should have a main breaker and the ground and neutral bar should be tied together. Here you will also have the building steel ground attached.

There should be 4 wires to the second panel, since it is a sub from your main, and the grounds and neutrals should NOT be tied together there.

Quote:
3) Should they then be connected to the ground rods (if needed at each service panel)? or Should the grounds and neutrals be seperated and only the bare grounds connected to the grounding rod?
See #1.

Quote:
I've gotten conflicting reports from different sources. You guys seem to be the most knowledgeable from what I've read in other posts on this site.
You got that right

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Old 12-16-2008, 01:58 PM   #3
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Confused About Grounding?


Thanks InPhase 277, your post makes a lot of sense, but it raises another question for me.

Quote:
There should be 4 wires to the second panel, since it is a sub from your main, and the grounds and neutrals should NOT be tied together there.
This fourth wire you mentioned from first panel to the second panel. Is this just a ground wire or is it somewhere connected to a neutral? In other words where is it to be connected in each panel.

Thanks
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Old 12-16-2008, 02:27 PM   #4
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Confused About Grounding?


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Originally Posted by nprranch View Post
Thanks InPhase 277, your post makes a lot of sense, but it raises another question for me.



This fourth wire you mentioned from first panel to the second panel. Is this just a ground wire or is it somewhere connected to a neutral? In other words where is it to be connected in each panel.

Thanks
After the first panel, the ground and neutral are separate wires. So, going to your second panel you need a ground. Right now that panel is grounded by the neutral. The neutral and ground should be physically and electrically separate in the second panel.

In other words, the second panel should have a ground wire run from the main panel, and that ground should be connected to a bar the second panel. Any existing connection from the neutral to the panel ground should be removed.
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Old 12-16-2008, 03:39 PM   #5
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Confused About Grounding?


InPhase277, one last question since you know this topic. Since I have an extra ground rod, would it hurt to ground the neutral and ground at the first box with a ground rod. I do not see where this box has any connection with the building's steel. It appears to be mounted only to wooden parts of the buildings structure with no contact with the steel.

Also, is there any size requirement for the fourth wire I need to run for the ground between the first panel and the last. The distance between the 2 panels is about 100 feet.

Thanks in advance, you've already been a tremendous help. I really was having difficulty trying to figure out how the person who originally wired this building got by. I purchased the mess a couple of years ago and thought nothing of it because everything was working OK. Then one day a circuit blew and the overhead lights in the stall barn started popping. I still probably don't know the full extent of the damage. I guess I should have inspected the electric setup BEFORE I started seeing problems. I'm hoping the lack of and/or incorrect grounding will remedy the situation.

Thanks Again, nprranch
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Old 12-16-2008, 04:26 PM   #6
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Confused About Grounding?


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Originally Posted by nprranch View Post
InPhase277, one last question since you know this topic. Since I have an extra ground rod, would it hurt to ground the neutral and ground at the first box with a ground rod. I do not see where this box has any connection with the building's steel. It appears to be mounted only to wooden parts of the buildings structure with no contact with the steel.
The code requires that the building steel be used as a grounding electrode where present. Of course adding the ground rod won't hurt, but it still won't meet the Code requirement for proper grounding. The only way to properly ground your system is to get a cable from your first panel to the building steel. The cable is sized by the cables that feed your panel. For example, if the wires coming into your main are 4/0 aluminum, you would need at least a #4 copper wire to the steel.

Also, if you have a metal water line feeding the structure, that needs to be grounded too. A #4 copper wire from building steel to the line would be acceptable.

Quote:
Also, is there any size requirement for the fourth wire I need to run for the ground between the first panel and the last. The distance between the 2 panels is about 100 feet.
This doesn't need to be any larger than #8 copper. I would run a green #8 THHN type wire. Available at Home Depot or Lowes.

Grounding is a complicated subject, and many electricians even fail to understand it fully.
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Old 12-16-2008, 05:58 PM   #7
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Confused About Grounding?


Can the OP measure ohms from panel ground to a cold water pipe and gauge whether he is properly grounded?
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Old 12-16-2008, 09:03 PM   #8
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Can the OP measure ohms from panel ground to a cold water pipe and gauge whether he is properly grounded?
No, because measuring resistance to ground would require a fall-of-potential test, not a standard ohm meter. Besides, we know that the neutral is grounded at the utility, so measuring to ground will always give some reading.
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Old 12-20-2008, 04:19 PM   #9
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InPhase277, I just got my grounding supplies purchased and I looked back over our past correspondence. I think I understood all of your posts, but I just would like to double check before I dive in.

Quote:
The only way to properly ground your system is to get a cable from your first panel to the building steel.
I'm assuming here since the grounds and neutrals are connected, I can run the ground to the metal building from the neutral bar (where both grounds and neutrals are connected)?


Quote:
After the first panel, the ground and neutral are separate wires. So, going to your second panel you need a ground. Right now that panel is grounded by the neutral. The neutral and ground should be physically and electrically separate in the second panel.

In other words, the second panel should have a ground wire run from the main panel, and that ground should be connected to a bar the second panel. Any existing connection from the neutral to the panel ground should be removed.
I understand the #8 THHN wire is connected to the ground bar in the second box completely seperated from the neutral bar. I've already made these completely seperate. As far as the other end of the #8 THHN wire (in the first panel), should it be connected into the neutral bar which is connected to the ground and thus the metal building ground or should it just be attached to the metal building ground??

This second question sounds stupid to me (and I really feel ashamed to ask it), since in the end they would all be together, but I just can't get it set right in my mind that it's OK to connect it to the neutral bar in the first box.

Just a little reassurance (or a correction if I'm thinking wrong), would be greatly appreciated.

Thanks in advance, you've been a great help....

nprranch
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Old 12-20-2008, 05:15 PM   #10
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Confused About Grounding?


Quote:
Originally Posted by nprranch View Post
InPhase277, I just got my grounding supplies purchased and I looked back over our past correspondence. I think I understood all of your posts, but I just would like to double check before I dive in.



I'm assuming here since the grounds and neutrals are connected, I can run the ground to the metal building from the neutral bar (where both grounds and neutrals are connected)?




I understand the #8 THHN wire is connected to the ground bar in the second box completely seperated from the neutral bar. I've already made these completely seperate. As far as the other end of the #8 THHN wire (in the first panel), should it be connected into the neutral bar which is connected to the ground and thus the metal building ground or should it just be attached to the metal building ground??

This second question sounds stupid to me (and I really feel ashamed to ask it), since in the end they would all be together, but I just can't get it set right in my mind that it's OK to connect it to the neutral bar in the first box.

Just a little reassurance (or a correction if I'm thinking wrong), would be greatly appreciated.

Thanks in advance, you've been a great help....

nprranch
Neutrals and grounds are all bonded together at the service entrance (1st fused service disconnect). Then they are always kept separate at all panels beyond this. At the SE(service entrance) you can put them both on the same bar or on separate bars if the bars are connected. Either way, they are all physically connected at the SE. Then they are isolated at other locations in the building.

The ground path and the neutral need to be bonded together at the service entrance for several reasons, including providing a fault path if there was a lightning strike or other overload to the SE cables. If they were not bonded at that first panel, then a fault on the incoming lines would not have any way to safely clear, and would take a path to the appliance of least resistance. Where if there is a ground that is bonded, that will hopefully be a path of lesser resistance to ground and take the majority of a fault.

You would normally connect the ground / bonding points such as rods, building ufer grounds, water pipes, etc to the main panel, then run a ground line of the correct size to the sub panel.

Hopefully Inphase can verify I am correct in what I said above, please correct me if I am wrong with any of this.

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Old 12-20-2008, 06:23 PM   #11
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Confused About Grounding?


One note here is that building steel is not an acceptable grounding electrode. If the steel in question is structural (framework) it is required to be bonded to the grounding electrode system at one of these places




From what you describe you have a farm pole distribution point and if that switch out at the pole doesnt have overcurrent protection (switch is a circuit breaker) then it may be your site isolation device. If more than one building is supplied from the pole then that is what it is and was installed by the utility... you should not do anything there.
If the first disconnection point is located at the horse/barn arena and is the form of a main breaker panel then this is your service equipment. I would say this is the case since you say only three wires enter your main panel.

Please refer to this thread to understand a bit about grounding. In the graphics the service disconncet shown is just a single disconnect enclosure so just look at it as your first means of disconnect (service equipment) at your horse barn that has the main breaker. Three service entrance conductors land in that disconnect and a 4 wire feeder leaves it to the sub panelwith neutral and ground isolated at the sub-panel. Neutral and ground are bonded in the service equipment enclosure so that fault and neutral current can use the service neutral to get back to the source transformer center tap.
Sub panel grounding
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Old 12-20-2008, 06:42 PM   #12
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Confused About Grounding?


Quote:
Originally Posted by nprranch View Post
InPhase277, one last question since you know this topic. Since I have an extra ground rod, would it hurt to ground the neutral and ground at the first box with a ground rod. I do not see where this box has any connection with the building's steel. It appears to be mounted only to wooden parts of the buildings structure with no contact with the steel.

Also, is there any size requirement for the fourth wire I need to run for the ground between the first panel and the last. The distance between the 2 panels is about 100 feet.

Thanks in advance, you've already been a tremendous help. I really was having difficulty trying to figure out how the person who originally wired this building got by. I purchased the mess a couple of years ago and thought nothing of it because everything was working OK. Then one day a circuit blew and the overhead lights in the stall barn started popping. I still probably don't know the full extent of the damage. I guess I should have inspected the electric setup BEFORE I started seeing problems. I'm hoping the lack of and/or incorrect grounding will remedy the situation.

Thanks Again, nprranch
The cause of the overhead lights popping and that blown circuit is most likely an open/bad neutral connection. In such a case, you would get a higher voltage (potentially as much as what is across both hot legs of your service) on the lamps and in any circuit that isn't wired across both hot legs (220V, 208V, etc)
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Old 12-20-2008, 06:51 PM   #13
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Confused About Grounding?


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Originally Posted by nprranch View Post

I'm assuming here since the grounds and neutrals are connected, I can run the ground to the metal building from the neutral bar (where both grounds and neutrals are connected)?
Yes. The building ground will land on any available terminal of the ground/neutral bar.


Quote:
I understand the #8 THHN wire is connected to the ground bar in the second box completely seperated from the neutral bar. I've already made these completely seperate. As far as the other end of the #8 THHN wire (in the first panel), should it be connected into the neutral bar which is connected to the ground and thus the metal building ground or should it just be attached to the metal building ground??
It too should land on any available terminal of the ground/neutral bar.

Quote:
This second question sounds stupid to me (and I really feel ashamed to ask it), since in the end they would all be together, but I just can't get it set right in my mind that it's OK to connect it to the neutral bar in the first box.
No need to be ashamed, it is a subject that is very confusing, as evidenced by Stubbie's post. In that he points out something that I overlooked. I am used to wiring steel buildings where the structural material is in direct contact with the earth or in concrete in direct contact with the earth. This may or may not apply to you.

Just to be on the safe side, you should drive a ground rod and connect it to your panel too. But that doesn't invalidate anything else you are doing. The steel must be bonded and the other panel must be grounded.
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Old 12-20-2008, 06:54 PM   #14
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Originally Posted by jamiedolan View Post
Hopefully Inphase can verify I am correct in what I said above, please correct me if I am wrong with any of this.

Jamie
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Old 12-20-2008, 07:11 PM   #15
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The cable is sized by the cables that feed your panel. For example, if the wires coming into your main are 4/0 aluminum, you would need at least a #4 copper wire to the steel.
Does anyone know if I have 1/0 aluminum wire coming into my first service panel, what would be the copper equivalent for grounding it?

Thanks

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