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ZBat910 09-07-2011 08:18 PM

Grounding Questions
 
Hey everyone I am new here and I figured I would sign up to learn some more about electrical work as I am pursuing an interest in getting an electrical license. First off let me start by saying I do have familiarity with electrical panels and HVAC work and have done several different jobs handling live circuits. I am very safe about it and my questions are only to help me grasp a firm understanding of how things work instead of trying to do my own project currently with a possible hazard. Basically I would like to know some more about grounding the meter box and main panels. I am going to spell out what I think is correct and if someone could just tell me if I am right or wrong or any other helpful advice that is correct and by code only.

From what I understand when you install say a 200 amp service in a home you must ground the entire system with 2 ground rods spaced 6 feet apart and must be 8 feet long with a maximum of 6" showing out of the ground. When the power company runs the service cable into the meter from a typical overhead service there is 2 hot wires and a neutral. The 2 neutral lugs in the meter are attached to the box itself for grounding purposes, is this correct? To correctly ground this meter it is my understanding that you will have a lug inside the meter for a ground connection which you will put a #6 solid copper wire unspliced from that lug in the meter down to a ground rod and from there to another ground rod with correct clamps being used. I know depending upon manufacturers I have found all kinds of panels that didnt have all the essential grounding kits with it and some must be bought separately. Does this apply for meters also? I dont really have much time spent inside a meter box and the last time was several years ago so I cant remember if there are lugs for grounding or not. I read on some forum of a guy suggesting hooking the #6 with the neutral on the load side on the same lug, is that ever done because that doesnt seem right to me at all. So if you do not ground at the meter and ground at the main panel how would you go about doing this? I am a little confused to which cable to run from the meter to the main panel in certain circumstances whether it be SEU or SER, how do you know what to run and also where would you hook the #6 copper in the main panel to ground efficiently? Sorry for so many questions but the NEC is very direct but can be hard to interpret and navigate at times so I wanted to get some professional opinions with someone I can talk to. Thanks for any response, I am sure i'll have some more questions later on but I really want to understanding these grounding principles first.

Jim Port 09-07-2011 10:18 PM

The ground rods must have 8' in contact with the earth. Ground rods are not the only type of electrodes allowed. Metallic water lines, Ufer grounds, plate electrode are other options.

Many power companies will not allow a grounding connection inside the socket. In this case the ground would go to the service panel. The bond screw would connect the panel enclosure and the neutral buss.

Type SE-U typically has 2 insulated and one concentric conductor. SE-R has 3 insulated conductors and a bare ground. SE-R would be used in a feeder application. SE-U would typically be used between the meter and panel and meter and weatherhead.

ZBat910 09-07-2011 11:05 PM

thank you for your response. i live in north carolina where most people tend to use ground rods and even so the water piping is becoming less popular for grounding or at least thats what some electricians say around here. inside a 200amp main panel you have the 2 lugs for the hot wires, the neutral lug in between them, a small lug next to that neutral lug, and also a separate lug for the ground bar on the side. if i wanted to run from the meter to this 200 amp panel it would be correct to use the SER with 3 insulated conductors and 1 bare ground right? i know in the main panel you would hook the two hot wires in those lugs, the white banded conductor in the neutral lug and the bare ground in the lug on the side attached to the ground bar. where would i hook all the connections inside the meter for this type cable? im being thrown off by the fact if i ran the SEU cable with only 2 insulated conductors and one bare ground that there would be an extra lug for the ground bar, what would go there? the #6 ran to the ground rods? also the other small lug next to the neutral lug in the panel is that used for another ground or what? if i had a power panel outside with spaces for breakers and also the meter all that is necessary is to ground to the rods from this panel and no need to run a #6 from the main panel in the house right?

Code05 09-08-2011 06:46 AM

Quote:

Originally Posted by ZBat910 (Post 723315)
First off let me start by saying I do have familiarity with electrical panels and HVAC work and have done several different jobs handling live circuits. I am very safe about it........

The fact you worked on live circuits makes you unsafe.

Code05 09-08-2011 06:47 AM

Quote:

Originally Posted by ZBat910 (Post 723444)
thank you for your response. i live in north carolina where most people tend to use ground rods and even so the water piping is becoming less popular for grounding

III. Grounding Electrode System and Grounding
Electrode Conductor

250.50 Grounding Electrode System. All grounding electrodes
as described in 250.52(A)(1) through (A)(7) that are
present at each building or structure served shall be bonded
together to form the grounding electrode system. Where
none of these grounding electrodes exist, one or more of
the grounding electrodes specified in 250.52(A)(4) through
(A)(8) shall be installed and used
.
Exception: Concrete-encased electrodes of existing buildings
or structures shall not be required to be part of the grounding
electrode system where the steel reinforcing bars or rods are
not accessible for use without disturbing the concrete.
250.52 Grounding

ZBat910 09-08-2011 07:15 AM

Quote:

Originally Posted by Code05 (Post 723526)
The fact you worked on live circuits makes you unsafe.

maybe i should have specified a little better. i have experience working around live circuits. Such as swapping a #10 romex wire to a #6 romex in the main panel to change the wire going to an air handler for hvac systems. Things like that. I did not mean i literally have live circuits in my hand and i work in those conditions. That is a way to get hurt. Nevertheless the purpose here was to understand grounding.

Code05 09-08-2011 07:31 AM

Here are some links to get you started.

http://www.mikeholt.com/newslettersA...categories.php

http://forums.mikeholt.com/showthrea...116#post656116

Go to post #36 in link above

http://www.mikeholt.com/freevideo.php?id=GVB2005

http://www.mikeholt.com/freegraphics.php?id=gvb

Code05 09-08-2011 08:02 AM

FYI: If I remember correctly the NC exam is 6 hours long with an average passing rate of 17%, so prepare to study hard.

Jim Port 09-08-2011 08:45 AM

Some areas require several thousand hours of verifiable experience in the trade before alowing you to sit for the test.

Code05 09-08-2011 09:12 AM

Quote:

Originally Posted by Jim Port (Post 723581)
Some areas require several thousand hours of verifiable experience in the trade before alowing you to sit for the test.

Yep. Average is 4 years or 8000 hours minimum.

Code05 09-08-2011 09:17 AM

Link to NC requirements.

http://www.ncbeec.org/modules/conten...%28b%29%281%29

brric 09-08-2011 10:50 AM

Your questions clearly indicate that you need some qualified help for this project, not online long distance advice.

Code05 09-08-2011 10:55 AM

Quote:

Originally Posted by brric (Post 723668)
Your questions clearly indicate that you need some qualified help for this project, not online long distance advice.

Yeah, I would say so.

ZBat910 09-08-2011 10:59 AM

yes you are correct it is a 6 hour exam and im sure the passing rate is pretty low. I am only 20 years old but have been on the payroll of a HVAC/Electrical business since I could get a workers permit at age 14 and i was employed even before then doing this kind of work. The reason i am unsure about some of these grounding questions is because its simply things that i did not have as much hands on experience with. I have a codebook and know how to study well since im in college but its easier to talk with someone. My uncle is a well established electrical contractor with an unlimited license and he happens to be well known on the board of examiners here in north carolina. I am quite sure i have 8000 hours but i know i definitely have the 4 years of employment that i could prove but ive also been told local inspectors can sign off on your experience and vouch for you as that is what my uncle did years ago to be able to take the test. I contacted the board of examiners myself and they did verify the 8000 hours/4 years experience but just to clarify do you need to meet BOTH of those requirements or just one of them to be able to take the test? And in response to brric i am not doing a project at all, you may have just misunderstood my wording in the first post about not doing a project and im just here to learn more.

brric 09-08-2011 11:48 AM

It would seem to me you would be far better served learning this from your 'well qualified' uncle. Just my opinion.


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