im a 1st yr apprentice, so this may be a dumb question.
how does bonding and grounding a electrical system make it safer??
am i correct in saying bonding the metal surfaces together would cause a cb to trip because the combined load would draw enough current to do so, in a ground fault situation?
and what is the purpose of the ground rod??
If your apprenticeship program does not provide it, I would strongly encourage you to pick up the latest edition of Soares book on Grounding and Bonding. It will have all your answers.
But in short, by bonding together all non-current carrying metal surfaces and raceways and such that are likely to be, or run the risk of, being energized in the event of a ground fault, you will have created an
effective ground fault current path which is, like you said, designed to facilitate the operation of the overcurrent device.
Remember that electricity in a circuit always wants to go back to its source as quickly as possible. So we force it to pace itself by running it through a load. However, if a ground fault were to occur and the bonding was inadequate, there is a likelihood that exposed metal surfaces could become energized, which is a hazard because if you went and touched it and you were grounded, you could get shocked. This is why we create the effective ground fault current path, so that fault current can travel through all the bonded metal parts back to the panel, across the main bonding jumper to the neutral bus, and thus back to the power source. It creates a low impedance circuit that allows a very high current to flow (Ohm's law), thus tripping the overcurrent device quickly.
As far as ground rods, I'm not as sure about those :smile: I believe there are a couple of functions. First, in a grounded system, you have a conductor (sometimes a neutral, sometimes a phase) that is grounded. This conductor is referenced to earth via your grounding electrodes: ground rods, ufers, underground water pipe, etc. This is a subject I'm not too well versed in, so the significance of this is blurry to me. Perhaps it helps stabilize voltage. Second, it allows a quick-and-easy path for lightning to travel if it strikes the building. I'm sure there are other purposes for system grounding but I'm not entirely sure what they might be.
Perhaps someone could elucidate (or improve/correct) my statements if they are in error.
Ugh, my wife is playing the MP3 of "Funky Town" by Lips, Inc. and I can't concentrate.
