Earth grounding requirements on industrial equipment.
Earth grounding requirements on industrial equipment.
(OP)
Can anyone tell me what NEC code article or IEEE std. spells out the requirements for earth grounding on industrial control panels? We are in the plastics extrusion business and have many machines that operate on 3 phase 480 power. All of out thermoformers, trim presses and pelletizers come from the OEM with the equipment grounding conductors installed and sized according to NEC specs in article 250. However, I seem to be having a problem when it comes to specific requirements regarding the grounded electrode system. The power comes into each machine from overhead busway fed from 3000 amp switchboard. Do I need a ground rod on each of the machine control panels? Inside the panels are relays, contactors, PLC equipment, motion controllers, power supplies, etc...
Any guidance is greatly appreciated.
Any guidance is greatly appreciated.






RE: Earth grounding requirements on industrial equipment.
RE: Earth grounding requirements on industrial equipment.
RE: Earth grounding requirements on industrial equipment.
RE: Earth grounding requirements on industrial equipment.
RE: Earth grounding requirements on industrial equipment.
You should carefully review definition of GEC (grounding electrode conductor). GEC and grounding electrode is not something you install at every 'equipment'.
GEC is the conductor used to ground the system's "grounded conductor" , such as neutral of 4 wire system, to the system’s grounding electrode, such as the building steel or a ground rod. Now this connection is typically made only at one point, which is the service entrance or the secondary of a transformer or in other words the origin of the system.
From that point onwards the "grounded conductor" (e.g. neutral) is not grounded again while a ECG (equipment grounded conductor) or the "green wire" is always installed with every branch circuit. (metal raceways are acceptable by Code as ECG, but let us not use it for the purpose of this discussion).
The only connection between the ECG and GEC is at the service entrance equipment or the secondary of a separately derived system.
Now if your 480V system is grounded at its origin and your machine does not require a neutral, you need not install the neutral but you install the ECG and "bond' all non-current carrying surfaces of the equipment (enclosure, frame, etc.) to the ECG. For extra safety you can "bond' such non-carrying surfaces to supplemental grounded surfaces such as building steel but not 'required' the code.
As for the grounding the static charges goes all you need is the all non- current carrying surfaces that a person can touch or span by standing at one location should be bonded together and eventually conncetded to a effectively grounded surface or a seprate grouding electrode and more importantly the "ground" chasis of the equipment generating static. If you are bringing your power feed with ECG (green wire) you should also connect that to this 'bonded' system. Now a seprate grounding electrode, if installed for this purpose is not your system grounding electrode but a supplemetnal grounding electrode.
RE: Earth grounding requirements on industrial equipment.
earthgrounding for nec designed buildings at the each piece of equipment is not a good idea it can cause ground loop currents that can lead to fires.
get yourseft a book on grounding per nec codes that has a lot of illustrations. have your boss pay for it. good luck
RE: Earth grounding requirements on industrial equipment.
You may want to try to eliminate the EFFECTS of your static problem by making sure that personnel are "UNGROUNDED", believe it or not!
Good luck! I hope you're able to resolve it all, ... at least so you can let us know what gives the best results!
RE: Earth grounding requirements on industrial equipment.
RE: Earth grounding requirements on industrial equipment.
RE: Earth grounding requirements on industrial equipment.
dpc is right. The Green Book is IEEE 142 Std (Recommended practice for grounding of industrial and commercial power systems) and should be complemented with IEEE 1100 Std (Recommended Practice for Powering and grounding sensitive electronic equipment).