250.118 - using emt conduit as a ground

[jap]

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]

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:



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.

 

[kwired]

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]

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>