NEC Grounding Question

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  #1  
Old 11-02-04, 04:31 PM
M
maspann
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NEC Grounding Question

My house has a Main panel on the outside (right beside the meter) that has a 200 amp main breaker, a 60 amp breaker for the heat pump, and a 90 amp breaker that feeds a sub panel in the house with all of the branch circuits. I am adding a 60 amp feader out of this main panel to supply a sub panel in a out building (120' from the main pannel).

My question is about the ground (or lack there of) in the main panel. It only has the 2 - 120 volt legs and the neutral. No ground. The feeds to the house sub panel and the heat pump are comprised of only the two 120v legs and the neutral. Question (1) Is this to code? There IS a ground wire attached to a ground rod that goes into the meter.

I did not check this before I pulled my wire to the out building, so I did include a ground wire along with three #6 THHN in 1" PVC conduit. I now am planning on driving a ground rod at the out building. Question (2) Should I remove the jumper between the neutral buss and the ground buss in the out building sub panel?

Thanks in advance!
Mark
 
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  #2  
Old 11-02-04, 04:49 PM
J
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It does not conform to today's code. But it may have conformed to code at the time it was installed.

If you run separate grounding and neutral wires to the outbuilding, then you must isolate the neutrals and grounding at that building.

Ground rods are required regardless. This is a different system.

Note that wires that connect panels to the earth serve a completely different purpose than wires that connect outlets to the panel. These two systems are currently both called "ground" systems, but that's about to change. The two separate meanings of the word "ground" have caused enough confusion for long enough.
 
  #3  
Old 11-02-04, 05:09 PM
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maspann
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Thanks John,

I failed to mention that the house is only about 3 years old.

Mark
 
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Old 11-02-04, 05:14 PM
J
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Is this a mobile home?
 
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Old 11-02-04, 07:36 PM
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maspann
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No, it is standard 1 floor 3 br ranch style. I have never seen the split main/sub panel for a house, but have heard it is common for new construction in this area.

Again, thanks for the input.
Mark
 
  #6  
Old 11-02-04, 07:44 PM
J
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Are the two panels connected with metallic conduit? If so, that is your ground.
 
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Old 11-02-04, 09:55 PM
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maspann
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Yes they are connected by rigid conduit....is that a dependable ground?
 
  #8  
Old 11-03-04, 06:33 AM
J
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Properly installed, it's dependable.
 
  #9  
Old 11-03-04, 08:59 AM
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Savant
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Just to cover the bases, I'd suggest AGAINST driving an addiitonal ground rod at this building unless you properly tie it in to the other grounds at your home. The code requires that all grounds (like ground rods, connections to cold water lines etc) be connected together so that they are a single ground source. So you can't have one ground rod at the house and another at this building running off two seperate lines. Since your service is grounded (as John mentioned) then there is no need to drive an extra ground rod. (since a ground line was run as you mentioned) As for the neutral/ground jumper on the sub-panel, you can remove it if this panel is being fed by another panel.

Regards,

Savant
 
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Old 11-03-04, 11:24 AM
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Savant, as I understand it, all grounding rods for the same building must be bonded. Grounding rods for an outbuilding are not necessarily bonded to the grounding rods for the main building. In this case, however, the EGC provides the bonding anyway.

A grounding rod for the outbuilding is not an option. It must be done.
 
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