Tech Tip: Minimizing Materials & Costs
Often in grounding grids it is common to see main grounding conductors sized at 250 mcm or larger. When wire sizes are at this level or larger, it may become difficult and expensive to make proper connections to ground rods (type GET). Since a single 3/4-inch or 5/8 inch ground rod would not be able to withstand several thousand amperes, a fault current must be distributed across an entire ground grid. Therefore an alternative to welding large gauge wires to ground rods would be to use an intermediary wire between the main grounding conductors and the ground rods. Typically 1/0 AWG wire can be used because this size wire has over 5 times the equivalent cross section of a 3/4-inch ground rod. This method not only simplifies the welding procedure, but also offers considerable savings of wire and weld metal.
| Grid Wire to Ground Rod Connection | |||
|---|---|---|---|
 |
 |
||
| Mold Type | Weld Metal | Mold Type | Weld Metal |
| GET 18-250A | #200 | GEE 18-250A | #90 |
| WT 250A-1/0A | #90 | ||
Several options for achieving a connection as specified in the engineering
drawings are available. All the examples below show electrically equivalent
connections as those specified in the engineering drawing represented
by the cross and circle symbol.
| Equivalent Connections to Ground Rods | |
|---|---|
 |
 |
| 1) 2 molds 2 welds | 2.) 2 molds 2 welds |
 |
 |
| 3.) 2 molds 2 welds | 4.) 1 mold 1 weld |
 |
 |
| 5.) 1 mold 1 weld | 6.) 1 mold 1 weld |
 |
|
Specification connection |
# 1 is the most common method |
