Art 250.52(A)(7)

[huntinchief]

I am an instructor at the US Army Prime Power School and need clarification on Article 250.52(A)(7). The article states that grounding electrode plates shall expose not less than 2ft² of surface to exterior soil. Does this mean that grounding electrode plates need to be 1'x2' thus 2 sq ft or will a 1' x 1' plate work with the idea that 1 sg ft of surface area on each side of the plate? I know this sounds silly but you'd be surprised at what students will argue about test questions.

 

[xformer]

IMHO, don't forget to add the area of the back side of the plate...

 

[infinity]

As you've noted the requirement is for the amount of surface area in contact with the soil. That would include the top, the bottom and the edges. Here's the section:

250.52(A)(7) Plate Electrodes. Each plate electrode shall expose not
less than 0.186 m2(2 ft2) of surface to exterior soil. Elec-
trodes of bare or conductively coated iron or steel plates
shall be at least 6.4 mm (1⁄4 in.) in thickness. Solid, uncoated
electrodes of nonferrous metal shall be at least 1.5 mm
(0.06 in.) in thickness