Using listed flexible metal conduit as egc

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Epalmateer

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Michigan
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Electrician
This is 100% hypothetical. Your allowed to use listed flexible metal conduit as egc as long as it's terminated in correct fittings and not longer than 6'. So, say you came from the panel with listed fittings and fmc that's 5' long to a metal junction box. Then you come off of that box with another piece 5' long to another box, so on and so forth. Would this technically be acceptable?
 
In the 1968 nec, 350-5 says that fmc can be used as grounding, no length limitations. So in a house built in 1968, if the house was wired in fmc, you would be grandfathered in to use grounded receptacles and use the fmc as a egc?
 
Epalmateer said:
This is 100% hypothetical. Your allowed to use listed flexible metal conduit as egc as long as it's terminated in correct fittings and not longer than 6'. So, say you came from the panel with listed fittings and fmc that's 5' long to a metal junction box. Then you come off of that box with another piece 5' long to another box, so on and so forth. Would this technically be acceptable?
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In my opion think no know it's dangerous to ever use a flexible metal conduit or even EMT to supply the very most important conductor. Yep the ground. Had a lazy electrician who used the EMT he ran to supply the ground on a 2" conduit. Less then a year after install conduit pulled out of fittings due to plumbers pulling on conduit to run a water line. When he went to reinstall the conduit back into the coupling wires that got knivked grounded out on load side and he almost got electrocuted. After that he always installed a ground wire.
 
garbo said:
In my opinion think no know it's dangerous to ever use a flexible metal conduit or even EMT to supply the very most important conductor. Yep the ground. Had a lazy electrician who used the EMT he ran to supply the ground on a 2" conduit. Less then a year after install conduit pulled out of fittings due to plumbers pulling on conduit to run a water line. When he went to reinstall the conduit back into the coupling wires that got knivked grounded out on load side and he almost got electrocuted. After that he always installed a ground wire.
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Not ground (see definition) but the EGC.
EMT provides a very low impedance fault current path due to it large area, there is a good review of EMT as an EGC is Soares Book on Grounding.
Issues with EMT coming apart are due to poor workmanship.
However many jobs require a EGC in EMT, but the NEC does not.
 
garbo said:
In my opion think no know it's dangerous to ever use a flexible metal conduit or even EMT to supply the very most important conductor. Yep the ground. Had a lazy electrician who used the EMT he ran to supply the ground on a 2" conduit. Less then a year after install conduit pulled out of fittings due to plumbers pulling on conduit to run a water line. When he went to reinstall the conduit back into the coupling wires that got knivked grounded out on load side and he almost got electrocuted. After that he always installed a ground wire.
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Root cause here is workmanship, not the EGC properties of EMT!
 
A very good review of this topic here

EMT as a ground path

I once had a copy of a Georgia Tech research paper that concluded that a long run of 1/2" EMT was a better ground than a #12 wire. Through testing they found that adding a redundant ground wire to this EMT did not decrease the fault clearing time of a short circuit. I had it saved on my...
forums.mikeholt.com
And there is a link to the Georgia Tech Study, I mentioned this study in a previous post.
 
garbo said:
In my opion think no know it's dangerous to ever use a flexible metal conduit or even EMT to supply the very most important conductor. Yep the ground. Had a lazy electrician who used the EMT he ran to supply the ground on a 2" conduit. Less then a year after install conduit pulled out of fittings due to plumbers pulling on conduit to run a water line. When he went to reinstall the conduit back into the coupling wires that got knivked grounded out on load side and he almost got electrocuted. After that he always installed a ground wire.
Click to expand...
The NFPA actually recognizes a metallic raceway (EMT in this case) better than a wire.

Roger
 
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