Need clarification on grounding

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Old 06-05-08, 07:36 AM
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Cool Need clarification on grounding

I'm allmost finished wiring a new 200 amp panel.I have a question on the groud and nuetral.My old panel was 50 amp.The ground from the ground rod was / is connected to the meter base.< the box itself>It is connected to the main panel<50 amp> via being metal conduit between meter and main panel.the nuetral was connected to a buss bar in the same panel.So ground and nuetral are basicly connected together in the old 50 amp panel.The new box will be connected to the meter box with conduit .So as of now there is no connection to the ground rod in the new panel. The neutral from the meter will be connected in the new box in the proper place.In the new main panel do I need to connect it to the ground rod?
Also the 50 amp panel has a ground wire connected to the cold water pipe.I have all pvc water line coming in the house now.No part of the metal water lines go into the earth now.Do I need to connect a ground from the New panel to the water lines?
 
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Old 06-05-08, 04:22 PM
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You need to run a #6 copper from the neutral/ground bus in the new main panel to the ground rod. You will need to run a #4 ground wire from the same buss to a metal cold water pipe closest to the point of where it enters the house. It doesn't matter if the pipe coming out if the ground is plastic. You are also bonding the water inside the pipe. Just find the closest pipe/fitting that is metal and bond it there. If you can't find any metal pipe/fitting, you may have to add a short piece of copper water pipe and bond it there.
 
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Old 06-06-08, 12:47 AM
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To make sure I got this right.The ground and nuetral will be tied gother in the main panel with a # 6 copper wire which will be connected to the ground rod.Should I leave the existing # 6 wire from the ground rod to the meter box in place? If so can I connect to the # 6 wire at the meter panel,or should I run a new wire from the main panel to the rod and have 2 wires connected to the ground rod?
The existing 50 amp panel has the water pipe grounded with a #4 copper wire.So I should be able to use that wire in the main panel to ground the water pipe?

Have an off the wall question.If the earth ground and the power neutral are tied together in the main panel.Then the ground and nuetral in my outlets are basicly the same connection.Just like in the old panel using the 2 hole outlet.Why do we need the three hole outlets?This is what really throws me a curve in trying to understand this grounding stuff.
Thanks for taking the time to answer my questions.
 
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Old 06-06-08, 05:26 AM
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The grounded conductor and grounding conductor are connected at the service panel, but they are two different things.

The grounded conductor carries current. The grounding conductor doesn't.

The grounding conductor is connected to the third hole in the outlet that we commonly call "ground". It connects to all metal and other conductive parts of the system to provide a lower-impedance path to ground than anything that might touch it, such as a human. (In a DC circuit, it's resistance. In an AC circuit it's impedance.)

Electricity wants to get to ground, and it will always take the path of least resistance/impedance. If you bond the neutral and ground at a receptacle, the metal parts will become energized. The metal case of a microwave oven, for example: Touch the energized metal case and the sink -- which is grounded through the pipes -- and that path of least resistance/impedance might be through you.

However, if you use grounding conductors to keep all of the metal parts of the system at ground, and the neutral is insulated from those metal parts except at one single point in the service panel, no lower-impedance path to ground can exist in the system. The microwave case and sink are now at the same (ground) potential.

I hope this didn't confuse you even more.
 
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Old 06-06-08, 07:57 AM
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Talking

Thanks Rick! That actualy makes a lot of sense to me.Just needed someone to "show me light" and " unground my mind".
But what about the ground rod,is it ok to tie the #6 wire from the main panel to the #6 wire in the meter panel?Or do I need to run another wire straight from the main panel to the ground rod?
 
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Old 06-06-08, 03:39 PM
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IF the existing #6 wire is long enough than run that into the panel and attach it to the neutral buss. If not, then you have to run a new wire because it is not legal to splice the wire (grounding electrode conductor) except in some very special ways. Same goes with the wire going to your water pipe.
 
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