I was reading the big picture post by george and there is still a few things I dont understand so forgive me but I am gonna ask. I dont understand why if you were to put voltage to a groung rod why you wouldnt trip the breaker. wouldnt this be a ground fault and what are the dangers of multiple ground to neutral bonding. I guess just in general I dont understand ground and neutral bonding. I just know where to do it but not really why
The Big Picture Post
- Thread starter fireryan
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peter d
Senior Member
- Location
- New England
fireryan said:
Simply put, the earth/ground rod interface has too much impedance (resistance) to trip a breaker at normal line voltages.
However, at utility voltages (7200, etc) a ground rod is quite effective.
JohnJ0906
Senior Member
- Location
- Baltimore, MD
Grounding - as in connecting to the planet earth, and grounding - as in bonding/providing a low impedance path to source to clear faults - these are 2 different things.
Check out 250.4(A)(1 through 5) Read the whole thing. Especially the last sentence of (5)
Check out 250.4(A)(1 through 5) Read the whole thing. Especially the last sentence of (5)
tryinghard
Senior Member
- Location
- California
fireryan said:
Electricity is not looking to return to earth, it is returning to its source. The earth ground connections primary function is to route lightning (static) to earth, static is looking for earth. But because the source is grounded somewhere upstream there is some parallel path of current during an extreme overvoltage situation, ?unintentional contact with higher-voltage lines?. This earth parallel path is usually high resistance and the resistance is unknown at any given moment.
Amperes = Voltage divided by Resistance (I=E/R), higher amperes than the circuit supplying breaker is required to open it, operate the overcurrent protection. 120V divided by 20 ohms resistance = 6 amperes meaning if this short to earth has 20 ohms resistance to its source there will only be 6 amps used therefore a 15A breaker will not open and the short will remain ? dangerous touch voltage will remain.
The danger of multiple neutral bonds is it is a parallel path for current. Voltage will travel all paths to source not only the path of least resistance. It is important to contain the returning current on a conductor and not allow it on other conductive items.
M. D.
Senior Member
fireryan said:
For more help see this series of articles..
http://ecmweb.com/mag/electric_grounding_vs_bonding/
They are great and easy to find using google ..
JohnJ0906
Senior Member
- Location
- Baltimore, MD
fireryan said:
You aren't the only one! :grin:
POCOs don't run an EGC. Therefore we have to connect the EGCs to the neutral (or grounded conductor) at the service entrance. Also, the NEC doesn't have any control over POCO installations. They are under the NESC, I think.
M. D.
Senior Member
fireryan said:
does anyone have the 1913 ROP from the NFPA??
Donald Zipse , would like to do away with the multi grounded neutral system
http://www.mikeholt.com/documents/strayvoltage/pdf/MultiGroundedNeutralFinal5-3-03.pdf
peter d
Senior Member
- Location
- New England
M. D. said:
I hope he lets us know how that works out for him.
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