The NEC requires all driven rods to be a minimum eight feet in the earth and for multiple connected rods a minimum spacing of six feet between rods. The width of the rod has little effect on reducing impedance to earth, however, the depth of the rod and spacing for multiple rods have a significant effect.
What is code for ground rods?
The only legal ground rod must be installed a minimum of 8-foot in the ground. The length of rod and pipe electrodes is located at 250.52(A)(5) in the 2017 National Electric Code (NEC).
Where are ground rods required?
If a single ground has a resistance of 25 ohms or less, building codes allow it to be used as the only grounding device. If the resistance of a ground rod is greater than 25 ohms, at least one additional ground rod is required.
Why are 2 ground rods required?
If it has a ground resistance of 25 ohms or more, 250.56 of the 2005 NEC requires you to drive a second rod. But many contractors don’t bother measuring the ground resistance. They simply plan on driving two rods because doing so will meet the requirements of 250.56, regardless of actual ground resistance.
What size ground rod is required for a 200 amp service?
#4
Grounding Wire
Ground wires for residences typically are made of copper and are #6 (6 AWG) or larger. for 200 Amp services, a #4 grounding electrode conductor (ground wire) is required.
Can I use rebar as a grounding rod?
Proper Grounding Rod
In most cases, pipe or rebar can be used. The grounding rod needs to be made of galvanized steel and also needs to be at least four feet in length for best results.
How far should ground rod be from panel?
NEC Article 250 does not specify a minimum or maximum distance between the main electrical panel and the ground rod. Because the panel must be connected to the ground rod by a buried copper wire, however, best practices suggest that the shorter the distance to the ground rod, the more efficient the ground.
Does a subpanel need a ground rod?
Yes, any sub panel outside of the main building requires it’s own ground rod and a ground wire back to the main building. And yes, a sub panel in the same building as the main does not need a ground rod – only the ground wire.
