250.118 - using emt conduit as a ground

jap

Senior Member
Wow 10 pages on a EGC in EMT!
As your self appointed resident code historian I will add that;
1/2" EMT (properly installed to NEC minimum) has a rating of 40 Amps as an EGC, 3/4" EMT has a rating of 60 Amps, 1" EMT = 100 Amps.
The conduit sizes were part of the equipment grounding conductor sizes from at least 1930 - 1965, what is T250.122 today.

The photo is from the 1965 NEC.

Cheers

I just love stuff like that.
It's so easy to read.

Thanks for posting.

JAP>
 

480sparky

Senior Member
Wow 10 pages on a EGC in EMT!
As your self appointed resident code historian I will add that;
1/2" EMT (properly installed to NEC minimum) has a rating of 40 Amps as an EGC, 3/4" EMT has a rating of 60 Amps, 1" EMT = 100 Amps.
The conduit sizes were part of the equipment grounding conductor sizes from at least 1930 - 1965, what is T250.122 today.

The photo is from the 1965 NEC.

Cheers

The same chart from 1937:

EMT as GND 1937.jpg

The language probably predates it back to the 1920, but it's sometimes difficult to trace as 1937 was the first major overhaul of the numbering system used.
 

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kwired

Electron manager
Wow 10 pages on a EGC in EMT!
As your self appointed resident code historian I will add that;
1/2" EMT (properly installed to NEC minimum) has a rating of 40 Amps as an EGC, 3/4" EMT has a rating of 60 Amps, 1" EMT = 100 Amps.
The conduit sizes were part of the equipment grounding conductor sizes from at least 1930 - 1965, what is T250.122 today.

The photo is from the 1965 NEC.

Cheers
That was 1965. THHN/THWN didn't yet exist, you almost never were going to exceed the rating based on what size conductors you could fit inside, exception maybe with a feeder tap situation. You also still had service conductors inside raceways with somewhat unlimited current limits.

I have easily exceeded the values in that table with more recent installs involving THHN/THWN and motor circuits.
 

jap

Senior Member
I bet those guys from way back then would get a kick out of how overly confusing we've made all this electrical stuff. :)


JAP>
 
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