Patient Care redundant ground

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nietzj

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St. Paul, Minnesota
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Electrician
In reading 517.13 it looks like I can use the metal conduit for one grounding path and a insulated EGC for the redundant ground in my patient care area. Is there any concern that the EMT in this case has a poor connection and thus I'm back to one ground? Just wondering if anyone just pulls in 2 insulated EGC's to be safe.
 
nietzj said:
In reading 517.13 it looks like I can use the metal conduit for one grounding path and a insulated EGC for the redundant ground in my patient care area. Is there any concern that the EMT in this case has a poor connection and thus I'm back to one ground? Just wondering if anyone just pulls in 2 insulated EGC's to be safe.
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never seen anyone do that. you still need the metallic wiring method for the primary equipment ground
 
As long as your wiring method meets the requirements of being an EGC and you pull a insulated wire EGC, I suppose one could pull an extra wire EGC, but I have not heard of this being common.

Three EGCs?
 
nietzj said:
In reading 517.13 it looks like I can use the metal conduit for one grounding path and a insulated EGC for the redundant ground in my patient care area. Is there any concern that the EMT in this case has a poor connection and thus I'm back to one ground? Just wondering if anyone just pulls in 2 insulated EGC's to be safe.
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You could pull as many wire type EGC's as you want to but the Metallic raceway is still required.

The NFPA considers the EMT to be the primary EGC and the wire is only a secondary.

Roger
 
Sometimes the conduit is also grounded at every support, unless its a wood framed building. Then all the building steel also helps.

For example, if the conduit is supported by bar joists, chances are there is a good ground path from one support through the steel to every other support. Then a loose coupling doesn't really make much of a difference in the effectiveness of the ground path.

If you are really worried about the conduit not providing a good ground path, you could also use threaded rigid steel conduit.

But most people generally don't see a need to go above and beyond the code requirements here.
 
jaggedben said:
..when all are properly tightened.
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But it doesn't really matter considering all the metal construction methods used in a typical hospital. You could pull a raceway apart and the strapping, inadvertent contact with framing members, bonding to other systems, etc.... would still make the required conduit EGC per 517.13(A) the main EGC.

Roger
 
steve66 said:
Sometimes the conduit is also grounded at every support, unless its a wood framed building. Then all the building steel also helps.

For example, if the conduit is supported by bar joists, chances are there is a good ground path from one support through the steel to every other support. Then a loose coupling doesn't really make much of a difference in the effectiveness of the ground path.

If you are really worried about the conduit not providing a good ground path, you could also use threaded rigid steel conduit.

But most people generally don't see a need to go above and beyond the code requirements here.
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jaggedben said:
..when all are properly tightened.
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You have to remember to put that wrench on the threaded RMC and tighten each piece also, or you may have some compromise to the bonding path.
 
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