Robert Nelson
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Can FMC be used, as a barrier, in a Pull Box that has normal and emergency power?
NEC Art.517
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If you are asking if as a continuous raceway enclosing conductors and running through the pull box, the answer would be yes.
Roger
brother
Senior Member
Im going to strongly have to say NO!! Emergency and Normal Power has to be COMPLETELY independent of each other, save for a few exceptions (ie transfer switches).
Just how "COMPLETELY independent" ? Maybe it should be in a different building? You don't even know the details yet.
brother
Senior Member
I dont know what the 'smart remark' was for, but NEC 2008 and 2005 517.30 (C)(1) is very clear. Not to mention article 700 Emergency Systems more specifically 700.9(B). Other than the exceptions listed, anything else would be a code violation.
Brother, say you had a surface mounted raceway going to the gantry of an xray machine, if you install a normal branch circuit in FMC along side open critical branch conductors in this raceway, they are effectively separated and independent of each other and 517.30(C)(1) is satisfied.
Of course the proper way to do it would be to use dividers (barriers) for the separation
Roger
Of course the proper way to do it would be to use dividers (barriers) for the separation
Roger
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cycotcskir
Senior Member
???
???
I must be missing something in the question. I read the question to mean that the FMC would terminate outside the box (somewhere) on both ends with the portion inside the box continuous. If that is correct, I don't understand why it needs to go through the box in the first place.
If both systems are entering the box from different conduits, then terminating in the box, then one switching over to FMC, then i would say no, but methinks I'm missing something here.
In any case, how about inserting a permanent divider in the box making it 2 boxes, one for each system.
???
I must be missing something in the question. I read the question to mean that the FMC would terminate outside the box (somewhere) on both ends with the portion inside the box continuous. If that is correct, I don't understand why it needs to go through the box in the first place.
If both systems are entering the box from different conduits, then terminating in the box, then one switching over to FMC, then i would say no, but methinks I'm missing something here.
In any case, how about inserting a permanent divider in the box making it 2 boxes, one for each system.
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brother
Senior Member
I suppose this really depends on the Ahj, As I have seen people try to do the 'divider' thing or run the conduit through something that had the normal and emergency and it did not fly if it didnt fall under the exceptions specifically listed in the NEC!! Completely independent means ' not attached to the other system in any way, (ie boxes raceways)
According to the inspector it really defeats the intent/purpose of haveing an emergency/backup system. If there was a fire/fault/overheating of of any sort that happen to the normal wiring they wanted to reduce the risk of it affecting the emergency side. If you just had both normal and e-power (ie light switches/receptacles) going to the same box and just put a divider/conduit run in it, and the normal side just overheated/faulted, it can still affect the e-side. I agree with the inspector.
The original intent of dividers for boxes or surface raceways that I see being used for seperation was to keep the voltages (120, 277) of adjacent devices from being over 300 volts NEC 406.4(G) 2008 receptacles and NEC 404.8(B) switches, or to run data and power etc... It was NEVER intended to be used for seperating e-circuits and normal circuits.
Just to add another point, you would notice that 406.4.(G) specifically mentions the 'barriers' between adjacent devices, so I believe if they wanted it to be ok for e-circuits and normal circuits , then it would've been mentioned. Nevertheless the Ahj for the area will enforce it how they see fit!
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Brother, I really don't know what you're talking about. Using your reasoning most CT scan installations, Pet Scans, MRI's, Xrays, Headwalls, etc... would never fly due to the fact that common duct systems with dividers are used to provide a raceway for LV systems, Critical branch conductors, Normal branch conductors, etc... to the equipment.
Roger
Roger
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