confused in my residential wiring class. i am reading alot today believe me ..

Discussion in 'General Electronics Chat' started by tony8404, Sep 13, 2008.

  1. tony8404

    Thread Starter Active Member

    Jun 11, 2008
    Hey everyone... i am in a residential wiring class right now and am having trouble understanding some basic stuff. we have not gotten in too deep yet so i would like to make sure i understand this now then get even more scrambled in the head.

    okay what i have going on is identified grounding wire and grounding wire... what is the difference as easy as can be taught to someone...

    if i dont make sense on my question i am asking from what i understand is there are neutral grounding wire, idientified grounding wire and unidentified grounding wire...

    i understand that the unidentified grounding wire is the hot wire.

    what i dont understand is the difference between the grounding wire and neutral wire???

    what i dont understand is why my book says neutral is neutral but can hold a voltage...

    what i dont understand is that there is 3 phase and single phase i understand it comes from the transformer from the power company but if there is 2 hot and one neutral why is it that the neutral can have voltage on it ?
  2. SgtWookie


    Jul 17, 2007
    I am NOT a licensed electrician - just to get that out of the way.

    "Neutral" is the power return path for current supplied by a "hot" wire.
    "Ground" is earth ground. It is there to protect operators from being exposed to lethal voltage potentials. If a ground wire/conductor is carrying current, there is a problem somewhere.

    In a residential service panel in the USA, there are two phases, L1 and L2 (for Line 1 and Line 2), that are "hot". They are 180° out of phase with each other. There is also a Neutral line.

    L1 and L2 are from opposite ends of the secondary winding of the power company's transformer, and Neutral is the center tap in that same winding.

    At the service panel, Neutral is connected to earth ground, usually an AWG 4 or larger solid copper wire that is connected to a long copper-clad grounding stake. This is to prevent the system from rising to arbitrarily high voltages, should a fault develop in the power company's transformer.

    The electrical service panel is the ONLY place that Neutral and Ground should be connected.

    If you plugged in a heavy load (say, a vacuum cleaner) at the end of a long wiring run, and measured the difference between Neutral and Ground, you might find several volts difference. That is because copper wire has some resistance, and the heavy load will cause a voltage drop across the resistance of the copper wire.
  3. SgtWookie


    Jul 17, 2007
    Just to illustrate the point:
    AWG 12 copper wire has a resistance of 1.588 Ohms per 1000 feet.

    Let's say that your run was 100 feet long. The Neutral wire should then have a resistance of 0.1588 Ohms from the end of the run to the service panel.

    Let's say that the vacuum cleaner represented a load of 10 Amperes.
    Ohm's Law says: E = IR, or Voltage = Current in Amperes x Resistance in Ohms
    Since you have both Ohms and Amperes known in this case:
    E = 10 x 0.1588, or 1.588 V.
    Since there is no current on the ground wire, there will not be a voltage drop between the service panel and the electrical outlet on the ground wire. Therefore, you can use a high-impedance digital voltmeter to accurately measure the voltage drop across the Neutral wire.
    Last edited: Sep 13, 2008
  4. Matsukaze

    New Member

    Apr 2, 2008
    You are confused about some basic things that you need to understand unless you want a career wearing a paper hat saying "Would you like fries with that?" Some of the terms you use don't make any sense. I don't think I can do an adequate job of explaining these things in the limited space available on this forum, and given the limited time that I'm willing to spend writing here, but you should be able to find the information you need if you look for it. Are you enrolled in a legitimate school or is it one of those scam trade schools that exists only to collect as much financial aid money as possible? If it's a good school, ask your instructor to explain what you don't grasp, and spend some time in the library. Read a couple of different basic textbooks; maybe one author's writing style will make more sense to you.
  5. SgtWookie


    Jul 17, 2007
    The OP is obviously quite new to the subject. Electricity and electronics are indeed very confusing to those who are undergoing indoctrination.

    This is a forum to inform, not to denigrate.

    You apparently have time to tell the OP that they have a future in pushing up the sales of french fries, but not the time to help them better understand the subjects that they are currently struggling with.

    If that is the BEST you can do, then get your sorry ass out of here.

    You owe the OP an apology for your selfishness and extreme lack of taste.
    Last edited: Sep 14, 2008
  6. Bernard

    AAC Fanatic!

    Aug 7, 2008
    SgtWookie gave a clean consice explanation ; all I have to add is ground wire is green, neutral is white ,hot is black . L 1 to gnd. 110-120 V,L 2 to gnd 110-120 V.L1 to L2 220-240 V. In the rare case of residental use of 3 phase there are 3 120 circuits to a common neutral, and 208 V between each pair of hot lines.
  7. gerty

    AAC Fanatic!

    Aug 30, 2007
    These answers depend on wher you live, but according to the National Electric Code: Ground wire can also be bare copper, neutral can also be grey. Rules vary greatly from one location to another,in the US they can be stricter than the NEC but not more lenient.
    For example, where I live, in the city the neutral is grounded to the ground rod at the weatherhead and in the service panel, out in the county it's only connected at the panel.
  8. JRM1


    Aug 30, 2008
    I am concerned about this statement.
    "i understand that the unidentified grounding wire is the hot wire."

    To the best of my knowledge, a grounding wire should never be a hot wire.

    "what i dont understand is the difference between the grounding wire and neutral wire???"
    The neutral and the ground wire are both connected together back at the distribution panel. The neutral wire carries the current from the load back to the panel to complete that circuit. The ground wire is defined by the NEC as a non current carrying conductor. It is to be a low resistance path to carry fault currents back to the panel. In the event of a short circuit the ground wire should carry enough current to trip the breaker or blow the fuse and stop the fault current.

    "what i dont understand is why my book says neutral is neutral but can hold a voltage..."

    If a load is connected in a circuit and somewhere after the load the neutral wire is broken (open circuit) the the neutral wire after the load all the way to the break in the wire is hot. It will have the same voltage as the hot wire.
  9. tony8404

    Thread Starter Active Member

    Jun 11, 2008
    sgt. wookie thanks for sticking up for me. sorry i have not checked my post since i posted. this is some good info. i now understand the grounding wire and neutral wire... i did mis type some of the terms by accident due to me not having the book in front of me and was trying to remember the terms at the time...

    i had a quiz last night on switches and wiring up 2 s-way switches and a 4 way along with one lamp. i messed up the wiring diagram on the quiz had a total brain fart. but now after knowing i messed it up i somehow have it locked in my head i believe i will be looking for some pratice worksheets on wiring and what not.
    the reading is not bad in this new book they gave us. its called residential wiring. alot of the text talks and refers to the nec code book which i have as well but my instructor told us to use the nec code book not to try to memorize it. so with that said when i read the chapters i read but will skim through the code parts which almost sumarizes the chapters by half. is this a good technique to use right now cause i am trying to get the basics down and will let the code part follow when i do the hands on which i think is the way to go. i am not going to my trade school to be an electrician its a class that we take but i really wanna know this stuff to do work in my own home.