Effectively Bonded or not?

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ggonza

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Picture this: The seismic requirements on a job require that the feeder conduits coming out of the Main switch gear start out with flexible conduit, for at least a foot. Then they can adapt to whatever works after that. In this job I'm on we went FMC out of the top and then converted to EMT. Some of the runs go with EMT all the way to their destination. But some other pipes go out the building and convert to PVC. All the Conduits in question that go to PVC have conductors that are protected with 225A, 400A, 800A, and 1600A OCPD. Therefore the FMC between the EMT and the switchgear does not qualify as an equipment grounding conductor per 250.118. I believe the EMT in question is ineffectively bonded for handling ground fault current. My co-workers disagree because they say your allowed to use FMC by itself in any length anyways. And as long as you pull a seperate egc, then no worries. I feel like I have no leg to stand on because, why would the code require all non current carrying parts of an electrical system to be proprely bonded, but at the same time let us use FMC thats not an egc. because it would still need to carry its own ground fault current if a fault happened in the middle of a run. Any comments or answers would be cool, thanks.
 
If the short section of FMC does not qualify as an EGC then how is the EMT properly bonded? I agree with you.
 
I agree to. Maybe thier thinking it's allowed. Because I think some type of MC cable is allowed to be used as an equipment ground.
 
Take a look at 348.60 and 250.118 and you will have a leg to stand if the ocpd is above 20 amps. I can't see how these design spec's would not require an egc ran in each conduit and bonding bushings with jumpers are required. I believe you may be in California?
 
jeremysterling said:
I disagree. The OP has pulled an EGC, or he alludes to that fact. How is the EMT not bonded? I believe that the EMT is bonded by the EMT connector in the gear where the EGC terminates.

If the "greenfield" is connected to the EMT, it is bonded.

However, If the FMC is isolated on both ends by PVC, can the FMC be bonded by an external bonding jumper?
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The FMC is between the swtichgear and the EMT. If the FMC does not qualify as an EGC how is the EMT bonded?
 
yes thanks I understand that. but what about using any FMC over 20A. It seems that there is a gray area around this. In order for all non current carrying parts to be effectively bonded, you wouldn't be able to use FMC over 20A because it would be metallic (needs to be bonded) but not an egc itself. So how could you argue using it?
 
ggonza said:
yes thanks I understand that. but what about using any FMC over 20A. It seems that there is a gray area around this. In order for all non current carrying parts to be effectively bonded, you wouldn't be able to use FMC over 20A because it would be metallic (needs to be bonded) but not an egc itself. So how could you argue using it?
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d. Where used to connect equipment where flexibility
is necessary after installation, an equipment
grounding conductor shall be installed.

If you read all of the artices in the previous post you will see that a bonding jumper is required between the FMC and EMT. Again what do the spec's require?If they are requiring the FMC at the the switch gear there will be a clause regarding the bonding.
 
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