NEC ARTICLE 517-13A-1996 NEC

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PAUL BAKER

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I HAVE USED PVC UNDERFLOOR TO FEED BRANCH CIRCUITS IN EXAM ROOMS AT A DOCTORS CLINIC. THE INSPECTOR HAS SAID THAT THE CONDUIT HAS TO BE METALLIC TO THE PANELBOARD FEEDING THE BRANCH CIRCUITS. ACCORDING TO THE CODE I UNDERSTAND THAT THE CONDUIT HAS TO BE METTALLIC BUT IT DOESN'T MENTION ABOUT GOING TO THE PANELBOARD. I WOULD THINK TO A J-BOX ABOVE THE CEILING WOULD SUFFICE. ALSO, WHAT IS THE INTENT OF THE CODE,OTHER THAN JUST REDUNDANCY, FOR GROUNDING IN THIS SITUATION? IF THAT IS THE CASE, WHY WOULD NOT AN ADDITIONAL GROUNDING CONDUCTOR INSTALLED WITH THE BRANCH CIRCUITS DO THE JOB EXCEPT FOR THE FACT THAT YOU ARE NOW PARALLELING CONDUCTORS SMALLER THAN 1/0?
 
Re: NEC ARTICLE 517-13A-1996 NEC

I have been told that the logic for conduit and ground wires separately, vs two ground wires, is that the two ground wires will terminate at the same location in the same manner. If the ground bus comes loose, both ground wires are loose. However the conduit is still connected to the case, and hopefully the grounding system.

I'm not sure I completely understand it, but that is what I was told.

Jim T
 
Re: NEC ARTICLE 517-13A-1996 NEC

You are not paralleling conductors. You are placing a conductor (specifically the equipment grounding conductor) in parallel with the raceway. That is a redundancy whose sole purpose is safety, as Jim T described.

Since the EGC does not normally carry current, you are not creating a hazard by having parallel paths. The only time an EGC does carry current is when there is a fault. At that time, you want there to be a high current, so that the breaker will trip and terminate the event.
 
Re: NEC ARTICLE 517-13A-1996 NEC

It does mention about going to the panelboard. The code specifies branch circuits, so that would be from panelboard to outlet inclusive. A jbox above celing could be used to switch from EMT to health care type A/C cable.

If you mean the feeder to the panelboard then, no it can be PVC.

Unfortunately you're stuck with running RMC or IMC below slab
 
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