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Old 11-06-2008, 09:00 PM   #1
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Confused about grounding.


I have been stuggling to figure out a fairly simple grounding question I'm sure many here would understand.

I have a home built in 1961 with 2 wire electrical wiring that has no groundwire, and a fusebox. Outside there is a thicker wire that goes into the ground. Here are my questions.

1. Is the wire outside going into the ground where the neutral goes to, or is that a ground (I didn't think I had one.)

2. If I run new wiring with a groundwire, would I screw the groundwire to the neutral busbar since I don't think there is a ground busbar?

Thank you for any help. I'd really like to run some new wiring, but not sure what to do with the ground wire in the cable on the fusebox end of the circuit.

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Old 11-06-2008, 09:29 PM   #2
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Confused about grounding.


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1. Is the wire outside going into the ground where the neutral goes to, or is that a ground (I didn't think I had one.
Nope not the neutral....this likely is your grounding eelctrode conductor that is connected to a ground rod. Has nothing to do with the equipment ground in your house branch circuits...it is primarily there to help in protecting your premise wiring and equipment brought on by lightning strikes or utility power surges. If you have metal water pipes you should also have a wire going to a connection point on a water pipe close to where it enters the house.

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2. If I run new wiring with a groundwire, would I screw the groundwire to the neutral busbar since I don't think there is a ground busbar?
Yes, the equipment grounds would land on the same bar with the neutrals in the panel if that panel is the service equipment where the main disconnect for the dwelling is located. Do not put grounds with neutrals in the same terminal hole. Only one neutral per terminal don't double them. You can generally put a couple grounds together of the same size.

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Old 11-06-2008, 09:41 PM   #3
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Confused about grounding.


Ok, that is helpful. Thank you. A follow up.

You mentioned metal waterpipes. We do have them, however, there is no ground of any kind connected to them that I am aware of. Does this change anything you said?
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Old 11-06-2008, 10:46 PM   #4
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Confused about grounding.


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Ok, that is helpful. Thank you. A follow up.

You mentioned metal waterpipes. We do have them, however, there is no ground of any kind connected to them that I am aware of. Does this change anything you said?

Not really, but the rod was most likely added later, so you should. What type of cable do you have in your house? You might be able to replace some of those 2 prongs...

Last edited by rgsgww; 11-07-2008 at 10:21 AM.
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Old 11-07-2008, 01:01 AM   #5
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Confused about grounding.


I'm not sure what post #4 was about but you are required to have a water pipe bond if metal pipes exist for your water supply. A connection with an approved water pipe clamp is made within 5 feet of where the metal water pipe enters the house. This is a requirement not an option. Usually #4 solid copper is used. It doesn't however change anything as to the premise wiring and it not having an equipment ground. You will simply run your new branch circuits and connect their neutrals and grounds to the same bar in the panel.
The idea is to bond them at the service equipment so that fault current and neutral current can utilize the service neutral to return to the utility transformer. Right now you only have neutral or grounded legs in your branch circuit wiring and no equipment ground and therefore no ground fault protection. Your new branch circuits will provide ground fault protection as you will be bonding all likely to be energized metal from any faults to the neutral bar in the service panel via the equipment grounding conductor. This will allow any fault currents to return to the transformer and this will facilitate the opening of the circuit breaker for the faulted branch circuit. See the diagram below....
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Confused about grounding.-bonding-diagram.jpg  
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Old 11-07-2008, 10:23 AM   #6
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Confused about grounding.


How far is your water main from the breaker panel?
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Old 11-07-2008, 04:25 PM   #7
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Confused about grounding.


Wow this is an excellant diagram. I plan to look at it closely tonight after work when I have more time. Thank you for the response. More than likely, I will ask more questions after studying your response. I have really been trying to figure this out so that if I run new wiring, I can use updated cable and ground the recepticles. My house has obviously serviced for a half century without ground, but where possible, I'd like to do it right.
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Old 11-07-2008, 04:26 PM   #8
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How far is your water main from the breaker panel?
Other side of the unfinished basement. About 35 feet. We redid all the plumbing when we bought the house. Removed all galvanized supply lines and installed all new copper.
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Old 11-07-2008, 06:53 PM   #9
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Confused about grounding.


So in the diagram, the electrial fault doesn't even travel to the ground rod and the water pipe ground. Is that normal?

Is it a safe and normal practice to attach the ground wire to an empty spot on the neutral bus bar like you mentioned? I understand they seem to bond together anyhow. I just didn't realize that the ground fault would travel all the way back to the transformer. I thought it had to go into the earth. Thanks again for this info.
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Old 11-07-2008, 08:35 PM   #10
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Confused about grounding.


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So in the diagram, the electrial fault doesn't even travel to the ground rod and the water pipe ground. Is that normal?

Is it a safe and normal practice to attach the ground wire to an empty spot on the neutral bus bar like you mentioned? I understand they seem to bond together anyhow. I just didn't realize that the ground fault would travel all the way back to the transformer. I thought it had to go into the earth. Thanks again for this info.
Electricity travels in complete circuits. Faults are no different. The earth is not part of the circuit path. It is, however, part of the circuit that lightning travels. We only tie our neutral to the earth in case of lightning strikes or high voltage line cross overs.
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Old 11-07-2008, 08:45 PM   #11
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Confused about grounding.


So even in a completely up to date, up to code house, the ground faults will travel back to the transformer? Good to know. I guess I thought the fault traveled into the earth?!?

So this is why the ground can be tied into the neutral bus bar...they go back to the same place anyhow! I'm getting smarter already. Much appriciated. Glad you guys don't mind alot of questions from wannabes.
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Old 11-07-2008, 09:19 PM   #12
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Confused about grounding.


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Originally Posted by noisyone View Post
So in the diagram, the electrial fault doesn't even travel to the ground rod and the water pipe ground. Is that normal?

Is it a safe and normal practice to attach the ground wire to an empty spot on the neutral bus bar like you mentioned? I understand they seem to bond together anyhow. I just didn't realize that the ground fault would travel all the way back to the transformer. I thought it had to go into the earth. Thanks again for this info.
Yep its safe and the only place you do this is at the service equipment. Service equipment is the first means of disconnect that the service conductors land on. This can be either a stand alone disconnect and then a sub-panel at the dwelling or a main breaker panel. If your service panel is a main breaker panel then the equipment grounds, grounding electrode conductors, and neutrals are all bonded to each other at the neutral bar and the metal of the panel. You will also notice the service neutral is connected to the neutral bar. Current always seeks its source (transformer) and it will take any path available to it to get there. We intentionally construct a low impedance/resistance path back to the transformer with the equipment grounds and bonded metal. Current will take any path available to the source but it will travel the path of least impedance/resistance if one is given for it to use. We give it only one of these low impedance paths.
Current will go to earth but earths resistance is much higher than aluminum or copper wire so the vast majority of your premise wirings neutral current and fault current (if any) returns to the transformer center tap via the lower impedance of the service neutral. So that being the case look at branch circuit neutrals and grounds as two lane highways that end at a one lane highway once it reaches the service panel. Only way to do that is to bond them to the neutral bar(s) which is bonded to the service neutral.
What is confusing you is the grounding electrode system and the equipment ground system. Grounding electrodes are for property protection and do little for human safety. Equipment grounding conductors are for ground fault protection for human safety and facilitate the opening of the circuit breaker to deenergize the faulted circuit.
If the current went to earth it likely would not be at enough amperage to open the breaker due to earths resistance to current flow. A reasonable value for the resistance of earth would be 25 ohms or more. 120 volts/25 ohms is 4.8 amps this wouldn't open a 15 amp breaker. So you see my point.
In contrast the resistance of copper or aluminum is in thousandths of ohms per thousand feet. So just taking a number at random 120/.525 ohms is 129 amps that will definitely open a 15 amp branch circuit breaker because that amperage (current) has to pass thru the breaker on its way to the transformer during a fault to bonded metal like the diagram shows occurring at the receptacle box.

Last edited by Stubbie; 11-07-2008 at 09:27 PM.
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Old 11-08-2008, 09:57 PM   #13
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Confused about grounding.


Can't tell you how much this information is appriciated. Not only am I trying to learn, I might be running some cable soon and until now was unsure of what to do with the ground wire, or if I could even use it.
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Old 11-08-2008, 09:58 PM   #14
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Confused about grounding.


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Can't tell you how much this information is appriciated. Not only am I trying to learn, I might be running some cable soon and until now was unsure of what to do with the ground wire, or if I could even use it.
You should still have the water pipe bonded with the panel.
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Old 11-09-2008, 12:03 AM   #15
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Confused about grounding.


what if there is metal conduit. if that is is grounded properly then you could just add grounding recepticles with a ground strap to the conduit, correct? and not have to run all new wire.

Mikeee

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