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Conduit Grounding/Bonding in CLI, DIV 2

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jcfoley

Mechanical
Feb 18, 2005
90
I hope you folks can help me out here. I am a mechanical engineer but have had to deal with controls for quite a few years. I now have an electrical PE pounding me for information on grounding/bonding practices. I have seen this done several different ways. I know that NEC requires equipment housings and conduit to be grounded but it never really says how this is to be done. Here is the situation.

1. The equipment housing ground screw is connected to a ground wire and brought back to the panel ground.
2. Rigid conduit is installed to the equipment.
3. Liquidtight conduit is used to make the connection to the panel.

Questions

1. Is a separate external bonding jumper required for the liquidtight section?
2. If I use an external bonding jumper on the liquidtight section, can I eliminate the ground wire inside the conduit (thereby using the rigid conduit as the equipment grounding conductor?
3. If I gound the equipment housing directly to the equipment skid via an external grounding terminal, is any of the above necessary?


Any suggestions are welcome.


 
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Recommended for you

1) Yes, see 502.16
2) Yes, but standard locknuts cannot be used for the conduit, see 502.16
3) An equipment grounding conductor is required to be installed with the circuit conductors. Remote, external equipment grounding conductors are not permitted as the fault clearing path. See 300.3(B).
Don
 
Equipment (motors) grounding conductors are covered on NEC 250-95; a grounding conductor is required which size must comply with table 250-94 based on the size of largest entrance conductor or table 250-95 based on the current rating of automatic over-current device in circuit, ahead of equipment.
 
aolalde,
The conduit itself is premitted to be used as the required equipment grounding conductor (see 250.118 or 250-91(b) in your code book), even in classified areas. I don't think that is a good practice, but it is code compliant. Also, Table 250.66,(250-94 in the '96 and earlier codes) is not normally used for sizing equipment grounding conductors. That is for the grounding electrode conductor.
Don
 
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