Grounding conductor for Branch Feeder

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STRUT12034

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We have a existing building built in the 50's, the sub panel feeders are below grade in rigid conduit, no grounding conductor exists except conduit ground, is it permissable to install a grounding coductor to the panel board in a seperate path to the main ground bar at the distribution panel?
 
STRUT12034 said:
We have a existing building built in the 50's, the sub panel feeders are below grade in rigid conduit, no grounding conductor exists except conduit ground, is it permissable to install a grounding coductor to the panel board in a seperate path to the main ground bar at the distribution panel?
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Not really, but the pipe is an effective ground path.

Read art. 300.5 (I)

300.5(I) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors shall be installed in the same raceway or cable or shall be installed in close proximity in the same trench.
Exception No. 1: Conductors in parallel in raceways or cables shall be permitted, but each raceway or cable shall contain all conductors of the same circuit including equipment grounding conductors.
Exception No. 2: Isolated phase, polarity, grounded conductor, and equipment grounding and bonding conductor installations shall be permitted in nonmetallic raceways or cables with a nonmetallic covering or nonmagnetic sheath in close proximity where conductors are paralleled as permitted in 310.4, and where the conditions of 300.20(B) are met.
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STRUT12034 said:
We have a existing building built in the 50's, the sub panel feeders are below grade in rigid conduit, no grounding conductor exists except conduit ground, is it permissable to install a grounding coductor to the panel board in a seperate path to the main ground bar at the distribution panel?
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The conductor must be run with the circuit. 300.3(B).

Is there reason to believe the conduit is not intact?
 
STRUT12034 said:
The existing conductors are an old RHW conductor in which we cannot get a fish tape by without fear of damaging them.
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I think what Bob was getting at is, is there any reason to believe that the metal conduit is not intact and not a viable equipment grounding conductor as permitted in 250.118?

Chris
 
Yes. That would be my question. Why do you need another grounding conductor? Are you concerned that the conduit no longer provides an adequate ground path?
 
I agree with others, it is ok as it exists.

but if you are in an industrial setting and OSHA 1910 subpart S (2007) and you need to work on it, you may be required to add the fourth wire to be compliant.
 
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