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Old 04-22-2013, 12:28 AM   #1
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Grounding


Forgive me if I use the wrong terminology.

So as I understand, you can use the EMT as the grounding conducter if it is bonded in the panel, correct?

So my question is, How many amps can that handle? For example if I run a 20 amp circuit, I would be required to use 12awg wire for the current carrying and nuetral conductors and should run a 12awg ground correct?

Same example - but say 50 amp 120/240 for a stove. Can 3/4" EMT provide a sufficient ground? What awg is the EMT considered? Is there anything in the code addressing this?

Just curious as to if the code addresses this. I know in theory the ground should carry no current.

Thanks,
Rick

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Old 04-22-2013, 03:06 AM   #2
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Grounding


Properly installed EMT is recognized as an equipment grounding conductor by itself. No further supplemental grounding is required.

If you install a 100 Amp circuit, then it's allowed to handle the grounding needs of that circuit. Tests have been conducted on the pipe to ensure there is adequate capacity for such use, and the Code recognizes this.

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Old 04-22-2013, 07:06 AM   #3
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Grounding


Properly installed metal conduit meets code as the equipment grounding conductor.

But I, personally, am suspicious that after many decades, the metal oxidizes and the current path can develop resistance. Note that at each junction box both the incoming and continuing conduits fit into metal sleeves with set screws to hold them in place. In turn the sleeves go into holes in the box and held on with lock nuts. It is not unheard of for the lock nuts to work loose.

Incidentally a 100 amp feed. with 2 gauge conductors, (not in metal conduit) needs an 8 gauge EGC. (Assuming copper wire)

I'm not sure whether electrical connections "self-cleanse" by having momentary heating of oxidized joints that welds the parts together for a suddently improved connection that stops the overheating before a total meltdown or fire. Such might happen with wire nutted EGC connections encountering a rare significant current flow.
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Last edited by AllanJ; 04-22-2013 at 07:15 AM.
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