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Author Topic: Floating Ground  (Read 4680 times)

Jonathan Johnson

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Re: Floating Ground
« Reply #10 on: February 21, 2016, 01:44:05 am »

Wood conducts if you hit it with enough voltage (like lightning), but then again so does air.  :o

That's why the wood is bonded to ground.  :P
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Doug Johnson

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Re: Floating Ground
« Reply #11 on: February 21, 2016, 02:22:03 pm »

Is it possible that there would be a jurisdiction where the uninsulated metal grounding lug on the right hand side would be considered a bonded
 grounding connection if the metal box cover was in contact with it when it was in place?
« Last Edit: February 21, 2016, 07:34:19 pm by Doug Johnson »
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Jonathan Johnson

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Re: Floating Ground
« Reply #12 on: February 21, 2016, 09:35:53 pm »

Is it possible that there would be a jurisdiction where the uninsulated metal grounding lug on the right hand side would be considered a bonded
 grounding connection if the metal box cover was in contact with it when it was in place?

That hardly seems possible, especially if the cover is painted. In the environment, I would think that unpainted metal would be subject to corrosion.
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TJ (Tom) Cornish

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Re: Floating Ground
« Reply #13 on: February 22, 2016, 09:00:05 am »

Is it possible that there would be a jurisdiction where the uninsulated metal grounding lug on the right hand side would be considered a bonded
 grounding connection if the metal box cover was in contact with it when it was in place?
The "bond" refers to the intentional connection between the neutral bus and ground bus at the service entrance.  From the picture I don't see any connection between neutral and ground. 

Are you referring to the possibility that the uninsulated ground lug may touch the lid and provide a ground connection?  That might be happening, but is not remotely acceptable, as it's not a positive connection and would be subject to both the wood backer and metal enclosure moving with temperature and humidity changes, not to mention rotting of the wood.

The NEC and UL go to great lengths to define specific methods and materials used for different situations.  The fact that an electrical path exists or that something appears to work does not mean a situation is acceptable.  One big reason for this is that circumstances change over time.  Certain materials will fail with age or elemental exposure, and some fault conditions only exist in combination with other temporary factors - i.e. an open ground connection will not become dangerous unless a fault occurs elsewhere, energizing grounded things that shouldn't be able to become energized.  This is why bad things can lay dormant for years or decades before being discovered, sometimes with tragic results.

Another example - NM cable is the yellow or white stuff used as in-wall wiring in houses.  It's perfectly suitable for that situation, however it can't be used as flexible cable, since the large-diameter conductors work harden with movement and will eventually break.  NM also cannot be exposed as the insulation is relatively weak, and any cut or abrasion will expose live conductors.  For exposed situations, conduit or metal-clad cable is required.
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Re: Floating Ground
« Reply #13 on: February 22, 2016, 09:00:05 am »


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