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#96236 - 11/10/05 03:36 PM Machinery Ground rods
Dnkldorf Offline

Registered: 12/12/04
Posts: 1091
Loc: nowhere usa
Walked into a plant this afternoon, to quote some work, and I am still noticing guys installing CNC machines, lathes, and such with ground rods by the machines.

I know manufacturers "require" this but the NEC is still somewhat unclear.

Under some excemptions you can put a ground rod if you want but the EGC from the feeder must be tied to it. You can't connect the ground rod by itself to the equipment without that being tied to the service ground.

See where i am going, I hope...

I remove them when I find them, after checking that an EGC was installed.

Am I on the right track?


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#96237 - 11/10/05 03:49 PM Re: Machinery Ground rods
resqcapt19 Offline

Registered: 11/10/00
Posts: 2209
Loc: IL
As long as there is an EGC run with the power conductors and connected to the equipment there is no reason to remove the rods. They do not have any adverse effect.

#96238 - 11/10/05 03:50 PM Re: Machinery Ground rods
Tom Offline

Registered: 01/01/01
Posts: 1069
Loc: Shinnston, WV USA
If the machine is properly grounded by an equipment ground run with or enclosing the conductors to the machine, then I see no reason to remove the supplementary electrode.

If the rod is required by the installation instructions furnished by the manufacturer of listed equipment, then it is part of the listing and labeling and should remain in place.

Few things are harder to put up with than the annoyance of a good example.

#96239 - 11/10/05 03:51 PM Re: Machinery Ground rods
iwire Offline

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
As long as the equipment is grounded to the source as required by the NEC they can add as many 'extra pointless' (supplementary) rods at machine.

250.54 Supplementary Grounding Electrodes.
Supplementary grounding electrodes shall be permitted to be connected to the equipment grounding conductors specified in 250.118 and shall not be required to comply with the electrode bonding requirements of 250.50 or 250.53(C) or the resistance requirements of 250.56, but the earth shall not be used as the sole equipment grounding conductor.

Notice that to the NEC Supplementary is entirely different than Supplemental
Bob Badger
Construction & Maintenance Electrician

#96240 - 11/10/05 04:10 PM Re: Machinery Ground rods
Dnkldorf Offline

Registered: 12/12/04
Posts: 1091
Loc: nowhere usa
Well, 2 things bother me,
One is the obviuos trip hazzard they posses.
Some of them run across the floor 5-6 feet, to where the ground rod was driven.

The second being, in part to how many I have seen wrong. This is where they didn't pull a EGC, and the ground buss bar inside the equipment was tied to the ground rod only.


#96241 - 11/10/05 04:45 PM Re: Machinery Ground rods
electure Offline


Registered: 12/24/00
Posts: 4229
Loc: Fullerton, CA USA
This is where they didn't pull a EGC, and the ground buss bar inside the equipment was tied to the ground rod only.

Keep in mind that an EGC doesn't necessarily have to be pulled.
Conduit also can be considered as the EGC under 250.118. "Wire" is only one of the fourteen acceptable items listed.


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