We are installing a new Laser at our facility. The manufacture recommends not connecting the system ground and just using a ground rod. They also recommend isolating the machine with a short section of non-metallic tubing. However the machine is still going to be connected to steel air lines and gas lines that are not isolated. These lines are tied to structural steel before they get to the Laser. Is this to code? It sounds pointless to me and I think the ground should be connected.
System Ground Vs Ground Rod
- Thread starter jellison
- Start date
- Status
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: System Ground Vs Ground Rod
Let?s be clear about our use of terms. Are you saying that the manufacturer recommends not connecting the external metal parts of the machine to an Equipment Grounding Conductor that is, in turn, connected to the neutral bar (at the main panel), and from there to planet Earth via a Grounding Electrode Conductor and a ground rod? If so, and I really tend to doubt that a manufacturer would say that, then I think it would be a violation of 250.4(A)(3).
If the manufacturer is attempting to make use of a separate ground rod as the sole means of establishing a path for ground fault current, then that would violate 250.4(A)(5).
Are you sure you are reading the manufacturer?s instructions correctly, for this sounds pointless to me as well?
Let?s be clear about our use of terms. Are you saying that the manufacturer recommends not connecting the external metal parts of the machine to an Equipment Grounding Conductor that is, in turn, connected to the neutral bar (at the main panel), and from there to planet Earth via a Grounding Electrode Conductor and a ground rod? If so, and I really tend to doubt that a manufacturer would say that, then I think it would be a violation of 250.4(A)(3).
If the manufacturer is attempting to make use of a separate ground rod as the sole means of establishing a path for ground fault current, then that would violate 250.4(A)(5).
Are you sure you are reading the manufacturer?s instructions correctly, for this sounds pointless to me as well?
brian john
Senior Member
- Location
- Leesburg, VA
Re: System Ground Vs Ground Rod
I have seen this specification before, the manufacture possibly has had wiring errors in the past and this illegal installation fixed the problem.
The manufacture is wrong and as stated this installation is dangerous, illegal and pay your insurance if you comply with their request. A proper installation done per the NEC is the only way to go DUH!
I have seen this specification before, the manufacture possibly has had wiring errors in the past and this illegal installation fixed the problem.
The manufacture is wrong and as stated this installation is dangerous, illegal and pay your insurance if you comply with their request. A proper installation done per the NEC is the only way to go DUH!
Re: System Ground Vs Ground Rod
I got downright forced to do this once with a piece of x-ray equipment. The only thing I managed to win was I would tie the ground rod into the buildings grounding system. If you completely isolate one piece of equipment from everything else you are definitely asking for problems and have an elevated shock hazard to your people.
I got downright forced to do this once with a piece of x-ray equipment. The only thing I managed to win was I would tie the ground rod into the buildings grounding system. If you completely isolate one piece of equipment from everything else you are definitely asking for problems and have an elevated shock hazard to your people.
Re: System Ground Vs Ground Rod
Perhaps the manufacture wants a single point isolated ground plane as we often do in the telecom buisness. It would involve either running a dedicated circuit from the N-G bond point in isolated conduit or PVC to the equipment. Or install a SDS and run isolated conduit or PVC to the equipment. Then the equipment is completly isolated from building steel, concrete, or any metalic structure.
The EGC would then form a single point isolated ground plane, and it would be impossible for any external curents like lightning, faults, or noise to flow in the equipment.
Perhaps the manufacture wants a single point isolated ground plane as we often do in the telecom buisness. It would involve either running a dedicated circuit from the N-G bond point in isolated conduit or PVC to the equipment. Or install a SDS and run isolated conduit or PVC to the equipment. Then the equipment is completly isolated from building steel, concrete, or any metalic structure.
The EGC would then form a single point isolated ground plane, and it would be impossible for any external curents like lightning, faults, or noise to flow in the equipment.
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