need to run a ground from motor across rubber isolation/dampening bars for vibration?

[emiller233]

When a 480vac 3-phase motor is mounted onto a rubber isolation/dampening bar (for vibration), do we need to run a ground conductor from the motor, across the rubber dampening bar, and onto the skid where this is mounted (picture attached w/ red arrows to the isolation bars)

The motors are just wired back to terminals inside of an enclosure (that is also mounted onto the same skid) thru rigid conduit and LFMC, where the customer will land their wires. if so, do we just follow table 250.122 for sizing?

motor dampening/isolation bars
http://www.ldi-industries.com/display/router.aspx?docid=42&blockid=1&injectedid=1885&

 

[infinity]

There needs to be a EGC run with the branch circuit to each motor. I see no code reason to install the jumper you've mentioned.

 

[ActionDave]

What is that extra wire from the motor frame to the skid going to do that the electrical enclosure and the metal conduits aren't doing already?

 

[emiller233]

i agree with you guys, and there is a EGC in the conduit to the terminal panel.

the customer is just fighting us that there should be. and i don't know what i can really use from the codebook to prove that we don't have to add this wire...

 

[infinity]

The NEC will not tell you that you do not have to do it. This is about as close as you will get. IMO almost no piece of metal is likely to become energized.

250.4(A)(4) Bonding of Electrically Conductive Materials and Other Equipment.
Normally non–current-carrying electrically conductive materials that are likely to become energized shall be connected together and to the electrical supply source in a manner that establishes an effective ground fault current path.

 

[emiller233]

this should be a big help, thanks guys!

 

[ptonsparky]

How much money can you make.by honoring his request?

 

[emiller233]

How much money can you make.by honoring his request?

None!, we tend to give stuff away to this customer......