Recently we wired alot of plastic injection machines, the manufacturer specified that each machine needs a seperate ground rod, after talking with the inspector, who says that if we do that we could send possible current up another ground rod if there was a short. Luckily we pulled a seperate ground wire back to the mdp, which in turn, is grounded directly to a ground rod. The manufacturer is now saying that becuase the mdp is 400 feet away it is not effective and they want the ground rods, but the inspector wont have it. any suggestions?
Ground rods
- Thread starter sjaniga
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- Status
- Location
- Illinois
- Occupation
- retired electrician
Re: Ground rods
250.54 permits the installation of this ground rod as long as the equipment has an EGC pulled in with the power conductors. The addition of this rod will not cause any problems. In my opinion there is no electrical advantage to installing this rod.
Don
250.54 permits the installation of this ground rod as long as the equipment has an EGC pulled in with the power conductors. The addition of this rod will not cause any problems. In my opinion there is no electrical advantage to installing this rod.
Don
Re: Ground rods
I go along with Don. There is no advantange to installing these additional ground rods. These individual rods probably have a higher resistance than functional (in otherwords wouldn't do anything) under the manufacturers expectations of "grounding"
Supplementary ground rods as far as say pole lights, have merrit as far as lightning, but I wouldn't immagine there is a big posibility of an inside lightning strike.
Roger
[ March 26, 2003, 06:22 PM: Message edited by: roger ]
I go along with Don. There is no advantange to installing these additional ground rods. These individual rods probably have a higher resistance than functional (in otherwords wouldn't do anything) under the manufacturers expectations of "grounding"
Supplementary ground rods as far as say pole lights, have merrit as far as lightning, but I wouldn't immagine there is a big posibility of an inside lightning strike.
Roger
[ March 26, 2003, 06:22 PM: Message edited by: roger ]
Re: Ground rods
As long as you installed an EGC conductor as Don stated, the AHJ does not have any say about it.
I also agree there is not much to be gained by it other than lower the high frequency impedance to earth, but does nothing in lowering any impedance back to the source.
If the manufacure is concerned about lowering the impedance of the fault path back to the source (MDP) then you can increse the size of the EGC's or add external bonding conductors, but adding ground rods will not lower the impedance back to the source, only earth.
[ March 26, 2003, 07:07 PM: Message edited by: dereckbc ]
As long as you installed an EGC conductor as Don stated, the AHJ does not have any say about it.
I also agree there is not much to be gained by it other than lower the high frequency impedance to earth, but does nothing in lowering any impedance back to the source.
If the manufacure is concerned about lowering the impedance of the fault path back to the source (MDP) then you can increse the size of the EGC's or add external bonding conductors, but adding ground rods will not lower the impedance back to the source, only earth.
[ March 26, 2003, 07:07 PM: Message edited by: dereckbc ]
james wuebker
Senior Member
- Location
- Iowa
Re: Ground rods
sjanigo, I work at a plastic molding company. We have all Engel machines. They say that we need a grounding rod for the machine even when we ran a grounding wire fron the main panel. We did do it the way they whated. The Engel service tech told us that you really didn't need one. He said that there's alot of plc boards in the machine. It will help the static charge from the machine and the materials that are run in the machine.I'm talking about the different types of resin plastic in the barrels of the machine. We just made sure that we sized the grounding wire properly. You'll 400 feet away from the machine and make sure you calclate any voltage drop in the run. If you want me to find out alittle more I'll call the factory about the ground rod. Bye
sjanigo, I work at a plastic molding company. We have all Engel machines. They say that we need a grounding rod for the machine even when we ran a grounding wire fron the main panel. We did do it the way they whated. The Engel service tech told us that you really didn't need one. He said that there's alot of plc boards in the machine. It will help the static charge from the machine and the materials that are run in the machine.I'm talking about the different types of resin plastic in the barrels of the machine. We just made sure that we sized the grounding wire properly. You'll 400 feet away from the machine and make sure you calclate any voltage drop in the run. If you want me to find out alittle more I'll call the factory about the ground rod. Bye
Re: Ground rods
I don't think the mfg understands the meaning of grounding. It does not mean installing a ground rod. As stated in the other posts your installation is proper but the distance of 400 ft may not provide a low impedance path. I assume you have used conduit. What size in the grounding conductor and what type conduit is inatalled?
I see no advantage installing a ground rod.
I don't think the mfg understands the meaning of grounding. It does not mean installing a ground rod. As stated in the other posts your installation is proper but the distance of 400 ft may not provide a low impedance path. I assume you have used conduit. What size in the grounding conductor and what type conduit is inatalled?
I see no advantage installing a ground rod.
- Location
- Illinois
- Occupation
- retired electrician
Re: Ground rods
The IEEE green book says that 1 million ohms is enough to prevent static build up. Just the normal contact between the metal parts of the machine and the concrete base or floor should be enough to eliminate any static problems as long as all non-conductive product handling parts have bonding jumpers around the non-conductive sections.
Don
The IEEE green book says that 1 million ohms is enough to prevent static build up. Just the normal contact between the metal parts of the machine and the concrete base or floor should be enough to eliminate any static problems as long as all non-conductive product handling parts have bonding jumpers around the non-conductive sections.
Don
Re: Ground rods
I have installed several of these types of machines and when I asked why we would have install aseperate ground rod at each even though we had included a properley sized egc. I was told by the manufacturer that because of the staic charge that the machine produces they spec a ground rod to help disapate that charge. In that same facility there is a waste grinder that didn't have a ground rod and was costantly "shocking" the operator. We checked after several reported iccidents and could not find an "electrical" problem. I ran the machine myself for about an hour and when I stepped off the rubber mat installed to prevent fatigue, I was met with a pretty good static zap from the frame of the machine. We istalled a ground rod and the problem went away. It seems as if the plastic boving through the machine was setting up a big static charge, kinda like a capcitor. Not a pleasnet feeling wheen you are about 10 feet off the floor feeding large sheets of plastic to the grinder.
Would this not be like having to include a grounding conductor in a dust collection system?
I have installed several of these types of machines and when I asked why we would have install aseperate ground rod at each even though we had included a properley sized egc. I was told by the manufacturer that because of the staic charge that the machine produces they spec a ground rod to help disapate that charge. In that same facility there is a waste grinder that didn't have a ground rod and was costantly "shocking" the operator. We checked after several reported iccidents and could not find an "electrical" problem. I ran the machine myself for about an hour and when I stepped off the rubber mat installed to prevent fatigue, I was met with a pretty good static zap from the frame of the machine. We istalled a ground rod and the problem went away. It seems as if the plastic boving through the machine was setting up a big static charge, kinda like a capcitor. Not a pleasnet feeling wheen you are about 10 feet off the floor feeding large sheets of plastic to the grinder.
Would this not be like having to include a grounding conductor in a dust collection system?
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