sdetweil wrote:
relaxin wrote:
all the metal components of an electrical system should be bonded together, not with separate ground rods, all cabinets, ground pins, boxes, fixtures etc etc get "bonded" which all goes back to source, the bond jumper on the neutral then facilitates a safe point of return for fault current, the earth has resistance and is only to be used as a back up encase the neutral in the service fails. the only time you make another Earth connection (with ground rods or plates) is if you run say a U/G triplex out to a distant building like a barn 300 feet away, at that point due to possible resistance in a reduced ground wire and the extra cost of aground conductor it is acceptable to leave the bod jumper on the neutral and install a ground rod set or ground plate. though recently it is strongly recommended for live stock building to have a separate ground back to source and sized appropriately, due to "tingle voltages" and the difficulty in eliminating them.
ok, now you have confused me. (do not bond at subpanels)
I have main service panel on the telephone pole under the meter. earth ground (via ground rod) and neutral are bonded.
then we have three buildings remote from the service panel with their own panels, each with an U/G triplex in plastic conduit.
house - 150ft
shop 1 - 130 ft
shop 2 - 75 ft
no ground wire to any of them from the service panel at the pole.
all three have individual ground rod created earth grounds.
none of these sub panels have neutral/ground bonded. (now)
OK in a situation like you describe, which is typical of a farm service, Here in Ontario we would have left in the bonding jumper between the neutral and the ground and installed a ground plate or rods at each panel that does not have a bonding(ground) wire going back to the main distribution point(the pole service in your case)
I would check with your local codes as to how that should be set up, as each jurisdiction can have a different opinion on how it should be done, not saying mine or theirs is more,, or less right.(that lends itself to where liability lies, done right or wrong "according to local codes")
The reasoning is to have any fault current in the grounded/bonded portions of the system (a live wire touching metal casing on say a fixture) carried back to the panel and back into the neutral, failing that, what could potentially occur is if something faults out, the earth your grounding plate or rods are in has resistance(soil type, moisture level, distance from other accepting sources ie transformer ground,) depending on the amount of resistance will determine the flow of power through it, it can be enough to restrict the flow so that the breaker or fuse does not trip or pop and cut off the flow so it stays live until something with less resistance makes contact with it, like say you in a situation where you are touching something else that can accept the flow of current easier than the earth.
a fun experiment you can try at home, drive a rod into the ground out in your yard hook only the hot line to it, plug it in, now make your feet wet, and start form about 100 feet away from the rod, and walk slowly in big 1 yard steps towards the rod, at some point you will feel a tingling sensation which will get stronger the closer you get, your body has less resistance than the earth,,,,, Honestly I don not recommend doing this on purpose,,, but if you must make sure you have someone on a switch to kill the power quickly. this is how people get shocked by downed live lines without even touching them, just an example of resistance in the earth, electricity is lazy and will always take the easiest path,
