# Equipment Grounding Conductor bonding rule to ground grid



## joebanana (Dec 21, 2010)

It should be grounded at the switchgear.


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## Power2engineer (Mar 6, 2020)

Hello Joebanana - Thanks for your reply. Clarification You say the motor frame should be grounded with a ground conductor running back to the power source switchgear. Does it have be a dedicated conductor running back to switchgear or can that be through the ground grid running throughout the facility?


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## skyline77 (Sep 6, 2013)

Check the following:
http://www.fiberglasstankandpipe.com/white-papers/general/static-ignition-hazards-when-handling-petroleum-products/


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## CoolWill (Jan 5, 2019)

Do you mean the pump circuit doesn't contain a ground, or do you mean the pump frame isn't bonded to the ground grid?


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## varmit (Apr 19, 2009)

The NEC would require that the bonding conductor be from the motor to the power source of the motor. In facilities such as refineries, where supplemental ground grids are installed to limit electrical potential differences between equipment, there are bonding "jumpers" installed to all pumps, motors and mechanical equipment from this supplemental grounding system.


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## Power2engineer (Mar 6, 2020)

1) The pump frame is not bonded to ground grid.
2) What do you mean when you ask Pump circuit does not contain ground? Do you mean that from the source switchboard a ground wire running to motor? If there is a ground wire from power source switchboard already running to motor it would be connected to motor frame ground and then there is no need to bond the frame to ground grid as long as the source panel ground is connected to ground grid. Isn't it?


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## brian john (Mar 11, 2007)

What type of cable or conduit do you have running to the motor?


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## [email protected] (Apr 12, 2020)

Its a common practice to Ground the motor frame at the Switchboard end. The cable connecting the motor to the Switchboard shall be of 4 Core cable, 3 cores each for R,Y,B and 4th core for frame earthing. 
If you are using 3 core cable, then Grounding of motor frame should be done at the Motor end. 
Its always prudent to have a dedicated or separate Electrode for earthing of storage tanks of flammable liquids. Although metallic containers may not require any dedicated earthing electrode as the tank body itself serves the purpose of discharging any static charges or Lightening discharges.
I recommend to not to combine the Earthing of motor frame with Earthing of Storage tank .


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## paulengr (Oct 8, 2017)

Refineries have their own Codes, API (American Petroleum Institute) standards that go beyond NEC. One if the major issues is that certain petroleum products such as gasoline develop static charges just from flowing in a pipe or hose, and that once in a while lightning can ignite vapors. So they have their own much more strict and aggressive rules on structure and electrical grounding that is beyond what NEC requires. So look there first.

Second strictly speaking the motor frame is a metal enclosure. So it must be bonded all the way back to the EGC just like everything else. So in a PVC conduit for instance a ground wire is required by NEC to the motor but in metallic conduits it’s supplemental. The general feeling (as in they are wrong) among a lot of engineers is that copper is a magical substance that must be present. But they are wrong. These guys do all the research and have very readable information on conduit:

https://steeltubeinstitute.org/steel-conduit/

One of the interesting things is that about 20+ years ago some information came out that you can’t realistically achieve good grounding beyond a certain distance.


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