Earth Rods in TN-C-S and TN-S

[LastManOnline]

Cookie the panel is probably 200 amps and the wire size should be 2/0 copper. Aluminum wiring would be 4/0 aluminum. We install 2 ground rods regardless of the resistance to ground. I have never read 25 ohms from the panel to the rod. It’s always less than 1 ohm. The # 6 wire is correct and if the conduit is metal yes it has to be bonded to the panel by means of a grounding bushing

Hi Megawatt. Am curious about your comment that you "never read 25 ohms from the panel to the rod. It's always less than 1 ohm".
2 questions
1) Does that means that YOU take fault loop impedence tests even though as Cookie mentioned earlier you are not obliged to do that if you have sunk 2 rods?
2) Am I correct to conclude that you always get a reading of less than one ohm every time you sink 2 rods? ie you have never had a situation where you found it necessary to sink a third rod in order to achieve a reading of less than 1 ohm?

 

[pc1966]

Below 10 ohms for a surge arrestor is a new one for me.

It is commonly seen in lighting protection guides. Not quite sure why that specific value though. For example, page 57 of this document:

https://www.erico.com/catalog/literature/E907W-WWEN.pdf

 

[davesparks]

Hi Megawatt. Am curious about your comment that you "never read 25 ohms from the panel to the rod. It's always less than 1 ohm".
2 questions
1) Does that means that YOU take fault loop impedence tests even though as Cookie mentioned earlier you are not obliged to do that if you have sunk 2 rods?
2) Am I correct to conclude that you always get a reading of less than one ohm every time you sink 2 rods? ie you have never had a situation where you found it necessary to sink a third rod in order to achieve a reading of less than 1 ohm?

Read his post again, he has never had a reading over 1ohm from panel to rod, that's the resistance of the copper or aluminium conductor between the panel and the rod. He's not talking about the rod's resistance to Earth.

 

[LastManOnline]

Read his post again, he has never had a reading over 1ohm from panel to rod, that's the resistance of the copper or aluminium conductor between the panel and the rod. He's not talking about the rod's resistance to Earth.

?

It is commonly seen in lighting protection guides. Not quite sure why that specific value though. For example, page 57 of this document:

https://www.erico.com/catalog/literature/E907W-WWEN.pdf

Good read that. Thanks for posting it.