Hello,
I understand the NEC provides the minimum requirements for saftey. My question is specifically regarding the resistance of the grounds at the service panel. As I read the NEC, it states you should have one 8' rod 10' deep, measure and if it exceeds 25 ohms you add a second rod. What if one is in an area of high soil resistivity and with the second rod only installed, the readings are still high e.g. 100 ohms or greater.
I understand that despite wheather a service ground was installed, a low resitance reading on the y system neutral would aid in ensuring the breaker trips in the event of a ground fault. What if the neutral has a high resistance e.g. 80-100 ohms?
Additionally, if the system has a delta secondary, the neutral and ground are not bonded together at the service panel, would one assume if there was not a service ground the breakers would likely not trip?
Thanks,
Dave Barker 5-May-08
I understand the NEC provides the minimum requirements for saftey. My question is specifically regarding the resistance of the grounds at the service panel. As I read the NEC, it states you should have one 8' rod 10' deep, measure and if it exceeds 25 ohms you add a second rod. What if one is in an area of high soil resistivity and with the second rod only installed, the readings are still high e.g. 100 ohms or greater.
I understand that despite wheather a service ground was installed, a low resitance reading on the y system neutral would aid in ensuring the breaker trips in the event of a ground fault. What if the neutral has a high resistance e.g. 80-100 ohms?
Additionally, if the system has a delta secondary, the neutral and ground are not bonded together at the service panel, would one assume if there was not a service ground the breakers would likely not trip?
Thanks,
Dave Barker 5-May-08