REDANDANT GROUNDING

[Toros]

HI
Can we use flexible meteal raceways that include complete circuit(s) plus two insulated grounding condactors
in medical / operatin rooms / in medical facilities
instead of green MC cable withextra grounding cond. ?????
thanx

 

[topgone]

HI
Can we use flexible meteal raceways that include complete circuit(s) plus two insulated grounding condactors
in medical / operatin rooms / in medical facilities
instead of green MC cable withextra grounding cond. ?????
thanx

If you are refering to the use of MC cables, IMO, the cable armor is not qualified as an equipment grounding conductor. Your MC cable should have a dedicated grounding conductor (green) as you posted. Please see 250.118.

 

[JFletcher]

HI
Can we use flexible meteal raceways that include complete circuit(s) plus two insulated grounding condactors
in medical / operatin rooms / in medical facilities
instead of green MC cable withextra grounding cond. ?????
thanx

No. The armor must qualify as a ground path; regular MC doesnt, even one with 2 ground wires.

 

[augie47]

Agree with the others. Two insulated grounding conductors can not serve as a substitute for
the raceway serving as a ground.
As you look at Art 517, there are a few very limited cases where FMC can be used but not as a substitute for a redundant grounding method.

 

[Toros]

HI
Can we use flexible metal raceways that include complete circuit(s) plus two insulated grounding condactors
in medical / operatin rooms / in medical facilities

 

[augie47]

HI
Can we use flexible metal raceways that include complete circuit(s) plus two insulated grounding condactors
in medical / operatin rooms / in medical facilities

As noted in post #4, in my opinion, there are a few limited locations where flex, if it qualifies under 250.118, can be used for flexibility but, in general, the answer is "no", regardless of the number of grounding conductors.

 

[roger]

Along with what the others have said, except for a few exceptions you can't use flexible wiring methods for the Critical and Life Safety branches either, see 517.30(C)(3)(3)

Roger

 

[don_resqcapt19]

It is nor just redundant grounding. The code wants an external metallic surface that is qualified as an EGC to help maintain equal potential between all conductive objects. A second grounding conductor within the raceway does not accomplish that.

 

[Jarp Habib]

No. The armor must qualify as a ground path; regular MC doesnt, even one with 2 ground wires.

The green MC the OP is talking about (if it is what i think it is) is listed for hospital use. It contains an uninsulated bonding wire in intimate contact with the armor that is sized according to 250 as a full equipment grounding conductor. Southwire HCF MCAP is the brand I'm familiar with, there may be others.

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