cschmid said:
Okay you are saying it has no role in clearing the fault yet you are routing the fault to earth. That sure looks like a role in clearing an fault to me.
No that is where you are stuck or confused. In NEC applications; fault or load current IS NOT permitted to use earth as a conductor. . Only in NESC applications is where earth is permitted to be used as a conductor for load and/or fault current. You need to grasp and understand this and why there is a difference. It has to do with Ohm’s Law. First consider an NEC application like a simple 20-amp 120 VAC circuit into a 25 ohm earth fault. 120/25=4.8-Amps. 4.8 amps is not a fault, it is a load to a 20-amp breaker. What ever point the contact is made at is now at 120 VAC only using Earth as a fault path. The breaker sees 4.8-amps as a normal load and is happy. You on the other hand now touch it, receive a shock, and wonder why because you think it is grounded. This is why the NEC forbids earth to be used as a conductor; it is simply not capable of doing so at low voltages because its impedance is too high to be of any use.
NESC applications are another story. Take a real simple example like a 20KVA transformer feeding your home. Assume the input voltage is 4160 fed with a 5-amp fuse, and that same 25-ohm earth impedance and tell us what you can figure out? Would the fault current be 4160/25= 167-Amps? Is 167-amps enough to operate a 5-amp fuse quickly and safely?
Soars book on grounding says " systems are solidly grounded to prevent excessive voltage to lightening, line surges, or unintentional contact with higher voltage lines and to stabilize the voltage to ground during normal operation"
Absolutely true, but they left out a couple of thing like; discharge static charges. All of which has nothing to do with clearing a fault on your side of the transformer at low voltages. Everything you just mentioned has to do with high voltages outside of your home either under the autority of NESC or God’s rules.
I never said the earth ground (Ground Electrode System) does not have a function, I am just saying it does not function the way you think it should..
I don't buy that a ground rod is not functional, other wise why would you get a shock on a faulty circuit on a trailer house when the frame is not grounded and yet it wont trip the circuit breaker and yet the panel is grounded.
Grounded to what? You need to use very specific definitions per NEC so we can understand your comments. Fault current under the scenario you just used will not use earth as a path, or at least any useful extent. Fault path is via the EGC, to the Ground Buss, through the Main Bonding Jumper, to the grounded circuit conductor, returning it to the source in which case is the utility transformer. There will be some current flowing through earth, but not enough to amount to anything useful or permitted
, it's better to have more than you need. I just have never had that experience in any field.
