I cannot locate the code reference for sizing of ground rods. 250.52(A)5 says the minimum approved rod is 1/2" but it never mentions when a 5/8 or 3/4 rod would be required.
I cannot locate the code reference for sizing of ground rods. 250.52(A)5 says the minimum approved rod is 1/2" but it never mentions when a 5/8 or 3/4 rod would be required.
Actually 250.52.(A)(5)(b) says that a ground rod is required to be at least 5/8" of an inch unless the rod is listed, then a 1/2" rod is permitted.
250.52(A)(5) Rod and Pipe Electrodes. Rod and pipe electrodes shall not be less than 2.44 m (8 ft) in length and shall consist of the following materials.
(a) Grounding electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size ¾) and, where of steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection.
(b) Grounding electrodes of stainless steel and copper or zinc coated steel shall be at least 15.87 mm ( in.) in diameter, unless listed and not less than 12.70 mm (½ in.) in diameter.
Rob
Moderator
All responses based on the 2014 NEC unless otherwise noted
There are way more unlisted ground rods on the market than there are listed ones. The cost associated isn't really worth it.
That being said, ground rod design is perhaps the most commonly over-engineered component of electrical systems I typically see on a daily basis. Engineers must have the inside track on ground rod futures...
Bryan P. Holland, MCP
NEMA - Codes & Standards
Everyone I have worked for in the past has specified a 3/4" diameter rod.
Thanks for all the answers. At least I know why I couldn't find the code section.
Last edited by petersonra; 09-09-09 at 01:20 PM.
Bob
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