total resistance of ufer ground electrode system

[paul hesson]

I was under the impression that a Ufer grounding electrode system had a total resistance of around five (5) ohms. Why would this not be low enough to open a circuit breaker under a ground fault condition with an open service drop neutral ?

 

[George Stolz]

Re: total resistance of ufer ground electrode system

It's not. Who said it was?

Edit: Sorry, I read too quick. That's not the ufer's intended function. It would allow 24 amps to pass, so a 20 amp breaker would eventually trip, true.

But a bolted fault on a 30 or 50 amp circuit would not open.

[ October 15, 2005, 11:08 AM: Message edited by: georgestolz ]

 

[don_resqcapt19]

Re: total resistance of ufer ground electrode system

It would allow 24 amps to pass, so a 20 amp breaker would eventually trip, true.

Maybe not. The trip curve for a major brand 20 amp breaker shows a trip time of between 60 seconds and never for a 24 amp load.
Don