Trying to understand why Ground rod needed?

[Kyell]

I am trying to understand why a ground rod is specified for a new CNC machine from Mitsubishi? They insist on this and my company's owner does not want it. I am trying to come up with a alternative such as running this external ground to a ground point with building steel. They (mitsubishi) insist the equipment grounding conductor will not suffice. Okay I would admit, when I ask Mitsubishi why their reply was the electronics need to be "earthed" and I will have dirty power from my EGC. Sorry but I want to scream .... the plant has a 480/277 bus duct system. Can someone help my understand their reasoning and why I should do as they suggest? I know code says I should install according to manufacture's installation instructions...

 

[electrofelon]

More manufacturer garbage. I wish these companies would just stick to what they do and not throw in stuff outside their scope that they apparently know nothing about. This probably creates more potential problems in fact.

 

[iceworm]

... the electronics need to be "earthed" and I will have dirty power from my EGC. Sorry but I want to scream .......

The equipment may well need a good ground to get some type of noise down. A local ground rod won't do anything. Don't forgot the NEC requires all the electrodes have to be connected. So, what ever noise is on your existing grounding/bonding system is coupled directly to the new earth rod.

Apparently dirt worshipers have infected Japan.

Still, one would think that any outfit that could build an A6M and super secret, super quiet, submarine propellers could keep the noise out of the electronics.

Do what they ask - if you can. Drilling through three floors and running 100' to get to dirt is a bit much. Remind them their dirt ground has to the connected to the rest of the grounding system. Point to the code section.

Close yourself in a closed, SCREAM. Come out and smile and bond. (Bond can either be make friends, or connect electrically - either will work.)

 

[infinity]

Nothing in the NEC prohibits installing these ground rods (auxiliary electrodes) even if they're worthless. {250.54}

 

[synchro]

This article from 21 years ago describes this very ssue. So it sounds like the manufacturers haven't changed their ways. I wonder how many current US installations are compliant with this requirement?

https://www.ecmweb.com/content/cnc-machine-tool-grounding-pleading-your-case

 

[petersonra]

I would just add the ground rod and not worry about it. It will serve no useful purpose including reducing "noise" but it will be easier than arguing with people over it.

 

[K8MHZ]

This article from 21 years ago describes this very ssue. So it sounds like the manufacturers haven't changed their ways. I wonder how many current US installations are compliant with this requirement?

https://www.ecmweb.com/content/cnc-m...ding-your-case

When I worked as a maintenance tech 25 years ago the company had us put ground rods at all the machines that had a certain kind of control on them. I thought it was stupid but I was paid to fix machines not design their installation.

 

[winnie]

It is required to improve employee satisfaction. Once you realize that it is not practicable to install the ground rod in the Earth below the machine, you will have to install a large flower pot to install the electrode. Once you have the large flower pot you will need to put a tree in to it. Once you have the tree the employees will be happier.....

 

[GoldDigger]

Just do not let them assert that you must not connect the EGC!!

PS: There is a non zero chance that the auxiliary electrode will increase equipment damage in the event of a lightning near strike, even with the EGC connected.

 

[Speedskater]

Forum member 'GAR' wrote a page about this exact problem.
http://www.beta-a2.com/noise_grnd.html

 

[StarCat]

Just do not let them assert that you must not connect the EGC!!

PS: There is a non zero chance that the auxiliary electrode will increase equipment damage in the event of a lightning near strike, even with the EGC connected.

This is the type of thing that Eric Dollard has warned about, and only a very small example......

 

[oldsparky52]

This article from 21 years ago describes this very ssue. So it sounds like the manufacturers haven't changed their ways. I wonder how many current US installations are compliant with this requirement?

https://www.ecmweb.com/content/cnc-machine-tool-grounding-pleading-your-case

Thanks for that.

 

[oldsparky52]

Forum member 'GAR' wrote a page about this exact problem.
http://www.beta-a2.com/noise_grnd.html

and Thank you for that.

 

[romex jockey]

So ok, help me do the math please:dunce:......if every machine has it's own GE , and they assumably have different ohmages to earth, what happens when they all assume a lightning strike of say, 1M volts?

~RJ~