Differences

This shows you the differences between two versions of the page.

--- reference:grounding [2015/08/07 21:23] – [Resources & References] Alan Shea
+++ reference:grounding [2017/01/29 01:13] – [Grounding Network] correct lead & tinned wire Alan Shea
@@ Line 16: / Line 16: @@
 If you live on sand like we do, use three ground rods (in several locations I've driven 3 rods deep, and they still pushed easily!). Ideally you want to get down to the water table.
-If you cannot drive ground rods because the ground is too rocky, dig a trench at least 2ft (or as deep as possible) and at least 20ft long and lay a #2 bare copper wire in it. You could also smash up some charcoal to mix in with the backfill. If you go this route I think it better to lay a ring all the way around the building. You must use exothermic welding (cadweld), brazing, or compression connectors for underground connections (in order of preference, and compression connectors should probably be augmented with brazing). Solder connections are not safe on ground wires, because the solder might melt during fault conditions. Solder is also not good underground because of possible galvanic action from the lead. Tinned underground wires are fine.
+If you cannot drive ground rods because the ground is too rocky, dig a trench at least 2ft (or as deep as possible) and at least 20ft long and lay a #2 bare copper wire in it. You could also smash up some charcoal to mix in with the backfill. If you go this route I think it better to lay a ring all the way around the building. You must use exothermic welding (cadweld), brazing, or compression connectors for underground connections (in order of preference, and compression connectors should probably be augmented with brazing). Solder connections are not safe on ground wires, because the solder might melt during fault conditions. Solder is also not good underground because lead and tin are sacrificial anodes and will pit and be gradually eaten or dissolved by galvanic action. This is also why tinned underground wires are not acceptable.
-Another option is to cast your bare ground wire in concrete; this is called a "Ufer" ground. It is very effective in rocky soil, very dry soil, or right on rock. The wire should be completely embedded 2" inside the concrete. If you're putting in a building, lay this right in the foundation footings. It needs to be no more than 2" from the soil, and its ok for it to contact the rebar. Longer is better, it can even be a ring in the footer all the way around the building. A ufer ground is now the preferred primary ground terminal for new construction in the USA, mainly because its permanent and can't be undone. The tail on the ufer ground should be long enough to connect to your ground bar or electrical panel.
+Another option is to cast your bare ground wire in concrete; this is called a "Ufer" ground. It is very effective in rocky soil, very dry soil, or right on rock. The wire should be completely embedded 2" inside the concrete. If you're putting in a building, lay this right in the foundation footings. It needs to be no more than 2" from the soil, and its ok for it to contact the rebar. Longer is better, it can even be a ring in the footer all the way around the building. A ufer ground is now the preferred primary ground terminal for new construction in the USA, mainly because its permanent and can't be undone. The tail on the ufer ground should be long enough to connect to your ground bar or electrical panel. Six inches of the copper wire should be insulated, covered with heat-shrink, or taped where it exits the concrete -- three inches inside and three inches outside -- to prevent the pH of the concrete from damaging the wire. (Inside the concrete, galvanic action does not continue once the concrete has cured.)
 If you want to do it right but less expensive than a commercial ground bar, buy a piece of copper bar from McMaster Carr (listing below). Mount the ground bar on ceramic insulators, or use blocks of hardwood for standoffs. Its preferable that it not contact the wall.

MetaTek

User Tools

Site Tools

Differences

Page Tools