6' ground rod

Status
Not open for further replies.
B

binney

Inactive, Email Never Verified
I witnessed a journeman factory/industrial electrician using 6' ground rods, to ground 3 machines in a cell. When and why is this legal?
 
it's not a NEC req . I do not have a copy of NFPA 79 that might give some guidance to this installation.
 
What about article 250.54 which lets you exclude article 250.50 which tells you to fallow 250.52 A4-A8. Article 250.52A5 Tells us that rods need to be 8' but 250.54 excludes us from this. Therefor can you use 6' ground rods for auxiliary grounding of equipment?
 
I'll be watching this thread

I'll be watching this thread

binney said:
I witnessed a journeman factory/industrial electrician using 6' ground rods, to ground 3 machines in a cell. When and why is this legal?
Click to expand...

I have witnessed the same also. (Driving Ground Rods in the middle of an industrial facility). (Black magic?, or "this is the way we always have done it")

IMO. If the 480v 3phase power conductors, and a properly sized GROUNDING conductor are fed to the industrial machine it meets NEC. This will protect personnel from shock hazzard, and will also enable the OCPD feeding the equipment to function, on a ground fault occurance of the phase conductors.

I have installed many machines with industrial rated programmable controllers, and instrumentation in them, and have NEVER used a ground rod. No problemo.

There have been many OEM of industrial machines that use a combination of industrial PLC's and a mish-mash of labratory grade electronics which do not use isolated measument circuitry, but everything referenced to a common ground plane. These electronic devices crap out at every blink of the eye. Then the OEM's just add a line of text into their installtions manuals, "need ground rod".

Personally, I would be aprehensive driving a ground rod in the middle of a facility. Who knows what underground utilities may lay underfoot? Water, gas, 120v, 480v, 13.2kv?

I am interested to see what inspectors have to say about multiple ground rods driven within a facitlity.

Thanks for the post
 
If the equipment is bonded to this rod in addition to an adequately sized EGC, then they are wasting their time, bolting the equipment to the floor does as much which electrically is nothing.
 
We just got in a new production line and it calls for 4 ground rods to be placed at points near the line. They call for them to be bonded to the rest of the grounding system.

It has more to do with the way the manufactures want there stuff installed. It gives them room to say it wasn?t installed to our specifications so the warranty is voided.
 
got_nailed said:
We just got in a new production line and it calls for 4 ground rods to be placed at points near the line. They call for them to be bonded to the rest of the grounding system.

It has more to do with the way the manufactures want there stuff installed. It gives them room to say it wasn?t installed to our specifications so the warranty is voided.
Click to expand...

Also known as HOODOO VOODOO grounding.
 
I call these time and materials electrodes.
The NEC nows calls theres auxillary electrodes. Most consider them ineffective. I say go ahead, as long as there is a EGC. The EPRI did a study and is says this grounding can create more problems then they solve, as there will be a difference of potential in a lighting strike and current can be introduced into the machine.
 
I agree with Tom, if they are supplemental or in addition to what is required, go for it and collect the check. Do not think the NEC has anything to say about it.
 
dereckbc said:
I agree with Tom, if they are supplemental or in addition to what is required, go for it and collect the check. Do not think the NEC has anything to say about it.
Click to expand...

Several years ago I saw an IMB main frame fried from a lighting strike on the auxillarly electrode, came in on the GEC through the main frame and flashed across the PVC isolation coupling (the only ground was the electrode no EGC to the service) then ran through out the plant.
 
Please elaborate on "IT"

Please elaborate on "IT"

got_nailed said:
We just got in a new production line and it calls for 4 ground rods to be placed at points near the line. They call for them to be bonded to the rest of the grounding system.

It has more to do with the way the manufactures want there stuff installed. It gives them room to say it wasn?t installed to our specifications so the warranty is voided.
Click to expand...

got_nailed,

Please type in the "exact" text of the OEM documentation that requires the (4) ground rods. You need not post thier name, or identify your equipment, I am just curious about... "new production line and it calls for 4 ground rods". Does the OEM documentation state any reasons for this? Codes? Warranty?

Thank You
IMM_Dr.
 
tom baker said:
I call these time and materials electrodes.
The NEC nows calls theres auxillary electrodes. Most consider them ineffective. I say go ahead, as long as there is a EGC. The EPRI did a study and is says this grounding can create more problems then they solve, as there will be a difference of potential in a lighting strike and current can be introduced into the machine.
Click to expand...

Mr. Baker,

Who is EPRI? Could you paste a link, or reference a document. I find this ground rod situation interesting and important.

My goal is to keep "ground rods" based in the realm of engineering fact, and would like to have documentation in hand when I see miss-application due to "hoodoo-voodoo", or I would especially like to flag out lab-grade electronics, that have no business in the industrial manufacturing environment.

Thanks for your time,

IMM_Dr.
 
tom baker said:
I call these time and materials electrodes.
The NEC nows calls theres auxillary electrodes. Most consider them ineffective. I say go ahead, as long as there is a EGC. The EPRI did a study and is says this grounding can create more problems then they solve, as there will be a difference of potential in a lighting strike and current can be introduced into the machine.
Click to expand...

dereckbc said:
I agree with Tom, if they are supplemental or in addition to what is required, go for it and collect the check. Do not think the NEC has anything to say about it.
Click to expand...


I agree completely as well.
The NEC does have some to say about the Supplemental/Auxilary rod(s) - Bond them to the EGC of the branch circuit/feeder supplying the equipment the rods are driven to supplement.



IMM_Doctor said:
Mr. Baker,

Who is EPRI? Could you paste a link, or reference a document. I find this ground rod situation interesting and important.

My goal is to keep "ground rods" based in the realm of engineering fact, and would like to have documentation in hand when I see miss-application due to "hoodoo-voodoo", or I would especially like to flag out lab-grade electronics, that have no business in the industrial manufacturing environment.

Thanks for your time,

IMM_Dr.
Click to expand...

Doctor
here are a couple of links

Explanation of EPRI

EPRI
 
I searched EPRI web-site, and did not lead to any definitive YES/NO for ground rods driven in the middle of an industrial facility.

I did Google searches about ground rods in idustrial facilities, and got many links. (One link back to Mike Holt forum in 2006).
http://forums.mikeholt.com/showthread.php?t=79400&highlight=light+pole+grounding This also discussed ground rods at individual machines.

Also got a hit from a very good article in ECM January of 2009. This article matched a few others that state that driving a ground rod at a machine (without bonding it directly to the exisitng grounding electrode(s), actually pose a greater risk than benifit.
http://login.ecmweb.com/wall.aspx?E...ding/avoiding_confusion_helps_customers_0109/

So at least the instrusctions given:
"We just got in a new production line and it calls for 4 ground rods to be placed at points near the line. They call for them to be bonded to the rest of the grounding system."
At least this manufacturer recognizes that.

But, all to often, I see the rod driven, and attached to the frame of the machine, or the same connection point as the EGC that comes in with the machines power supply feeder.
 
Status
Not open for further replies.
Top