Using Conduit as EGC
Using Conduit as EGC
(OP)
We are working on a project where a new 3000A swtichboard is being installed at an industrial facility, but the customer wants to use the existing conductors and rigid steel conduit for the feeders to all of the loads. None of them have equipment grounding conductors (EGC's) installed. While using the conduit as an EGC is legal per code, in almost all of our installations we do not do it; however, in this instance it might be necessary.
We can't find any sizing requirements for the conduit to be used in this way. NEC 250.122 does not give a specific size for the conduit based off of the breaker ampacity. Does such a table exist that we are missing, or is there an industry standard that's out there?
We can't find any sizing requirements for the conduit to be used in this way. NEC 250.122 does not give a specific size for the conduit based off of the breaker ampacity. Does such a table exist that we are missing, or is there an industry standard that's out there?






RE: Using Conduit as EGC
Bill
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"Why not the best?"
Jimmy Carter
RE: Using Conduit as EGC
RE: Using Conduit as EGC
https://steeltubeinstitute.org/steel-conduit/wp-co...
Annex B
RE: Using Conduit as EGC
RE: Using Conduit as EGC
Are these conduits installed above ground for their entire length (ie no underground portion). I am not sure of what the NEC says wrt U/G conduits, but in Canada (eh) the conduit cannot be used as an EGC if the conduit is installed U/G.
GG
"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)
RE: Using Conduit as EGC
RE: Using Conduit as EGC
https://steeltubeinstitute.org/steel-conduit/wp-co...
See Table 6.1 for instance.
RE: Using Conduit as EGC
For 3/4 inch Electrical Metallic Tubing with 4 x #10 AWG conductors, the maximum allowable run is more than Galvanized Rigid Conduit.
For 3/4 inch Electrical Metallic Tubing with 4 x #8 AWG conductors, the maximum allowable run is less than Galvanized Rigid Conduit.
Is this effect related to possible magnetic saturation of the conduits?
Comparing the results with rule 10-002 and table D3 of the Canadian Electrical Code, it appears that for loaded circuits it is safe to use the conduit as a bonding/grounding conductor.
In the case where a circuit is lightly loaded and the length based on the allowable voltage drop is increased, there may be issues, despite being allowed by the Code.
I did find the information interesting.
Thanks 7anoter4. lps
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Using Conduit as EGC
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: Using Conduit as EGC
Given the choice I'd install the earth continuity conductor, at least on the bigger circuits where there is less room for the earth loop impedance to rise due to corrosion and oxidation before the maximum disconnection time under fault conditions is exceeded.