EMT with an equipment ground run from an electrical panel to a disconnect, the EMT is used to ground the disconnect enclosure, the equipment ground from the electrical panel to the equipment is connected to a ground bar in the disconnect that is not bonded to the disconnect enclosure compliant or not code section please
EMT with equipment ground
- Thread starter mpd
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petersonra
Senior Member
- Location
- Northern illinois
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- Semi-retired engineer
take a look at 250.148
ptonsparky
Tom
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- EC - retired
- Location
- Chapel Hill, NC
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- Retired Electrical Contractor
Yes but that is unlikely since there is a disconnect involved.
ptonsparky
Tom
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- EC - retired
Not likely, but legal.
Just pointing out that an isolated ground is not a code violation. I have installed lathes in Machine shops that wanted an isolated EG. They got one. The conduit was also a suitable EG.
this is not an isolated ground installation, and 250.148 I am not sure if that would apply to a disconnect enclosure
- Location
- Chapel Hill, NC
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- Retired Electrical Contractor
Dennis I think you are correct, that disconnect enclosure would be considered a cutout box
- Location
- Illinois
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- retired electrician
I also disagree, and was thinking such even before I read Don's UL quote. 250.148 covers box grounding only. The metal shell of the disconnect which I believe you are discussing is an enclosure (FWIW the disconnect is likely considered a knife switch under Code).
For an enclosure, 250.134 applies, but does not specifically say where the raceway qualifies as an EGC, a redundant wire-type EGC must also be bonded where run in the raceway.
I conclude bonding the grounding bar to the disconnect enclosure is not required as it is with boxes.
I think he's saying the installer may have used the disconnect's neutral feed-through bus as an EGC feed-through bus... and it could be bonded to the enclosure by using the green screw (only if an SUSE disconnect).
Yes, I meant that the installer used the solid neutral bar as an equipment ground bar. When doing this the green screw must be used.
Carultch
Senior Member
- Location
- Massachusetts
How exactly would you get an isolated EGC? Isolated from what, exactly so?
Metal conduit gets you a continuous path from origin enclosure to destination enclosure, and at the origin enclosure, the premises EGC bar is built in, and electrically continuous with the enclosure. And that would be where I'd be deriving this "isolated" EGC.
If I take an Ohm-meter across both the separate EGC, and the destination enclosure, I will get a continuity buzz. That is anything but isolated.
What would such a machine require you to do? Put in a special grounding reactor between the isolated EGC and the general EGC?
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Isolated, in this context ONLY means isolated back to the single point where the EGC wires and the service or SDS neutral are bonded.
What it gives you is a ground reference to that specific point between the EGC network and the GES without the voltage offset (particularly at high frequencies) that may be caused by leakage current traveling over the primary EGC path (branch and feeder combined) feeding that branch and specific outlet wiring.
MasterTheNEC
CEO and President of Electrical Code Academy, Inc.
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I agree with this statement. The term cutout box doesn't default to mean a disconnect switch. However, a disconnect switch (knife, CB or otherwise) can be installed in a Cabinet or Cutout Box. Both of which are described in Article 100.
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