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  • OT Electrical Question

    My neighbor is building a garage and I was looking at the wiring which had been done by an electrician. The 220 volt circuits are wired with two conductors wire, black and white and bare copper ground wire. The white wire has black tape on it so the two black wires are the hot leads while the bare copper wire is common wire and there is no ground wire.

    When I was taught to wire 220 volt circuits many years ago, I was taught to use three-conductor wire (red, white, black and bare copper) where the red and black were the hot leads, the white was the common and the bare copper was the ground. Has the electrical code changed? If they are using two conductor with a bare ground for 220 volt circuits, will they be using single conductor black wire with bare copper ground to wire 110 volt circuits? This change seem like a step backward and unsafe way to wire.
    Last edited by BigBoy1; 01-26-2015, 07:12 PM. Reason: Typo!
    Bill

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  • #2
    I think you will find that the bare copper wire is the ground wire, and that a grounded conductor is not required. Normally you only need the grounded conductor when the 220 circuit is split into two 110 V circuits at the end of it.

    In other words, you would use the a three conductor with a ground wire if you were going to have two 110 V circuits plus one 220 V circuit at the end.

    Since apparently the circuits are wired as dedicated 220 V circuits, the white grounded conductor wire is not really needed.

    I am not up-to-date on the current code requirements though, so maybe someone who is can provide a more definitive response.

    Bill

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    • #3
      If this was a service installed in a separate building fed from the utility or from a transformer then it is treated as a service entrance. So the neutral is bare and bonded to the ground bar, and there will be a driven ground rod at this point. If it is a sub-panel fed from a service someplace else then it would properly have a four wire cable with the neutral and ground wires as separate conductors. It was common years ago to use just two insulated conductors and a bare neutral/ground wire to feed out buildings from a main building. This practice was stopped maybe 40 years ago as ground faults often found their way back to the service through the earth and caused havoc or even fires.

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      • #4
        even for today's codes, if you have a 240v ONLY circuit you use three wires - two hot and a ground, but no neutral. this is for things like welders, machinery, motors, or other items that only use a 240v circuit.

        newer items such as electric ranges and dryers now are wired to make use of four wires - two hot, one neutral, one ground. this is because they are technically 120v/240v appliances. the heating elements use the 240v circuit which only needs two hot and a ground, but the other bells and whistles are 120v and require hot, neutral, and ground, hence the need for four wires.

        by today's codes the ground is not intended to ever carry current except in a fault (short circuit) condition. older wiring schemes often combined the ground and neutral at the receptacle. this is what you see if you have an older house where you only have 3 prong receptacles for 240v appliances. the appliance ends up having the ground and neutral tied to the same plug , but any newly wired circuits are done with separate conductors.
        Last edited by lost_cause; 01-26-2015, 08:21 PM.

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        • #5
          In other words 4 wires to the panel in the shop & 3 wire circuits for machines, welder & such but 4 wires for most other 240v needs.
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          • #6
            Originally posted by BigBoy1 View Post
            My neighbor is building a garage and I was looking at the wiring which had been done by an electrician. The 220 volt circuits are wired with two conductors wire, black and white and bare copper ground wire. The white wire has black tape on it so the two black wires are the hot leads while the bare copper wire is common wire and there is no ground wire.
            Only safe for 240v only loads. IE well pump, dryer, large air compressor, etc. You must run a new wire (Most likely 2 new conductors+ground, or better yet 3 conductors + ground) for any 120v circuits you wish to power. Or you could change your 240v circuit over to 120v *only* by removing the black tape off each white wire and connecting it to neutral at the panel.

            But you just don't have enough wires for 120v and 240v loads.
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            • #7
              Originally posted by lost_cause View Post
              even for today's codes, if you have a 240v ONLY circuit you use three wires - two hot and a ground, but no neutral. this is for things like welders, machinery, motors, or other items that only use a 240v circuit.

              .
              Quite true, per NEC.
              Max.

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              • #8
                It WAS stated to be a 240V circuit, in which case it is fine.

                Plenty of 3 phase motors run on 3 wires plus an equipment grounding conductor. Not a thing wrong with it.
                1601

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                • #9
                  Guys,
                  Read my post about this being a 'service' which makes all the difference and is greatly misunderstood. Had this misunderstanding happen last week. I supplied a 480 to 120/240 transformer to power a RV trailer at a jobsite that had a four wire cord. Before plugging it in I tested the circuit. 240 phase to phase, 120 phase neutral, 80 to ground on one phase 150 on the other! I knew right away why. The electrician failed to treat the transformer as a new power source and bond the neutral to ground.

                  Appliances were a special case. The ground and neutral were not tied togther in the plug. They were allowed to use the ground wire as the neutral for the clock or timers. That was disallowed in the newer code. I grew up in the electrical business, my dad taught me all about this stuff 50 years ago.

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                  • #10
                    Originally posted by garyhlucas View Post
                    Guys,
                    Read my post about this being a 'service' which makes all the difference and is greatly misunderstood. Had this misunderstanding happen last week. I supplied a 480 to 120/240 transformer to power a RV trailer at a jobsite that had a four wire cord. Before plugging it in I tested the circuit. 240 phase to phase, 120 phase neutral, 80 to ground on one phase 150 on the other! I knew right away why. The electrician failed to treat the transformer as a new power source and bond the neutral to ground.


                    Appliances were a special case. The ground and neutral were not tied togther in the plug. They were allowed to use the ground wire as the neutral for the clock or timers. That was disallowed in the newer code. I grew up in the electrical business, my dad taught me all about this stuff 50 years ago.
                    unless i misunderstand it, the original post is about individual circuits and not a service entrance. i'm not an electrician and i readily admit that i am not 100% on all the jargon and lingo, but even so, the exact circumstances of the individual panel would need to be known (unless code has changed yet again). just a few years ago i converted the detached garage at my house to a working shop. i installed a panel that was powered from a 100a breaker in my house, and because of that sub panel situation, the ground and neutral were NOT supposed to be bonded. if i had chosen to have a meter put on the garage and power directly supplied to the panel from that meter, then the neutral and ground should have been bonded.

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                    • #11
                      Originally posted by lost_cause View Post
                      unless i misunderstand it, the original post is about individual circuits and not a service entrance. i'm not an electrician and i readily admit that i am not 100% on all the jargon and lingo, but even so, the exact circumstances of the individual panel would need to be known (unless code has changed yet again). just a few years ago i converted the detached garage at my house to a working shop. i installed a panel that was powered from a 100a breaker in my house, and because of that sub panel situation, the ground and neutral were NOT supposed to be bonded. if i had chosen to have a meter put on the garage and power directly supplied to the panel from that meter, then the neutral and ground should have been bonded.
                      That IS the standard setup, per code.

                      In certain circumstances, typically very long runs to farm outbuildings, or shorter ones to buildings housing animals, a local bond may be allowed. This is because the local earth may be at a very significantly different voltage than the remote earth where the bond is. It isn't entirely safe to have that differential, and specifically, it spooks animals when they get a shock on their nose from the feed container, etc.
                      1601

                      Keep eye on ball.
                      Hashim Khan

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                      • #12
                        Remote building panel: here it requires a ground rod. There are a few code exemptions and you can argue them, but you'll be told -bang in a ground rod. And a building disconnect unless the panel is with a certain distance of the door and less than 6 circuit. Sub-panel within the same structure - no bonding of neutral and ground. There are exemptions for single 120v 20 amp circuit fed by a GFCI.

                        NEC 2008 now specifies that the local and remote building grounding rods/bars are joined by a separate ground wire at least 6 (?) awg with specific sizing tables to look up. For light reading, look up NEC 250-32, but you local AHJ will always have the "correct" answer. For those that like to wade though it all, the Mike Holt Forums are a great resource.
                        Last edited by lakeside53; 01-27-2015, 02:27 PM.

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