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    #16
    Originally posted by growler View Post
    There is one difference. With voltage drop due to bad connection or undersized conductors you will never see lights get brighter or see a higher than normal voltage on one phase.
    Seen it before. Was pretty extreme case of small conductor for length of run, maybe 2000 feet of 2 AWG aluminum 120/240 feeder to a maintenance shed at a golf course.

    My first thought was bad neutral. We tried to find faults in that run and one or two of best possibilities we found with a fault locator we did dig up and found nothing. Finally came to conclusion there is just enough VD on the neutral to give similar symptoms of an open neutral. Think about it, if you load one line an neutral hard and have significant VD, the voltage of the unloaded line (or lightly loaded line) is going to go up in relation to neutral. If neutral were actually open and you only ran a single 120 volt load, it wouldn't work at all, we were still able to run a single 120 volt load.
    I live for today, I'm just a day behind.

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      #17
      I just spoke to one of my guys that was out there he was telling me he was getting fluctuating voltages from 112--118 phase to neutral, it was a hot day yesterday also so neighboring loads would/could make it dip even lower

      Sent from my SM-G965U using Tapatalk

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        #18
        190715-0957 EDT

        All the wires from the power company transformer to the main panel input terminals are likely the same material and size, and thus each has the same resistance. If an overhead line has a steel neutral and not adjusted in size and/or material for resistance, then neutral resistance could be higher. Measurements at my home imply about equal resistances.

        The hot path vs the neutral has additional impedance. Some in the transformer, in the meter, and the main breaker or fuse. The main breaker or fuse can be eliminated by making the voltage measurement on the wire at the main panel input. Thus, a slightly lower voltage drop occurs along the neutral path vs the hot path for a 120 load. A 240 V load produces no neutral voltage drop.

        If you go to the power company transformer and connect a test lead to the transformer's ground rod, or a screwdriver close to the rod, then you can do a direct measurement of the voltage drop of the power company neutral path to the main panel. But to a great extent you can get a good estimate of the neutral voltage drop by voltage measurements at the main panel input and various loading of 120 V phases, and 240.

        .

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          #19
          Originally posted by gar View Post
          190715-0957 EDT

          All the wires from the power company transformer to the main panel input terminals are likely the same material and size, and thus each has the same resistance. If an overhead line has a steel neutral and not adjusted in size and/or material for resistance, then neutral resistance could be higher. Measurements at my home imply about equal resistances.

          The hot path vs the neutral has additional impedance. Some in the transformer, in the meter, and the main breaker or fuse. The main breaker or fuse can be eliminated by making the voltage measurement on the wire at the main panel input. Thus, a slightly lower voltage drop occurs along the neutral path vs the hot path for a 120 load. A 240 V load produces no neutral voltage drop.

          If you go to the power company transformer and connect a test lead to the transformer's ground rod, or a screwdriver close to the rod, then you can do a direct measurement of the voltage drop of the power company neutral path to the main panel. But to a great extent you can get a good estimate of the neutral voltage drop by voltage measurements at the main panel input and various loading of 120 V phases, and 240.

          .
          Do if I hook up to the power co ground rod I put my other test lead on one phase is wat you are saying then I should have the correct voltage

          Sent from my SM-G965U using Tapatalk

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            #20
            190715-1024 EDT

            nickelec:

            Those are significant voltage changes. But you have to do some correlation with what is happening in the home or elsewhere. That is why you do your own controlled experiments with various loadings, and measurement points.

            Ir you personally are not there making measurements, then it may take a long time to solve the problem.

            .

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              #21
              Originally posted by nickelec View Post
              Do if I hook up to the power co ground rod I put my other test lead on one phase is wat you are saying then I should have the correct voltage

              Sent from my SM-G965U using Tapatalk
              Unless you have access to transformer secondary terminals to connect test leads there, you are somewhat limited to only testing for voltage drop on the grounded neutral conductor.

              One other problem you can have though connecting to the electrode at/near the transformer helps eliminate it, is measuring voltage that is actally drop from the primary distribution voltage system - since it's grounded conductor and the secondary grounded conductor are bonded together at the transformer they are essentially the same conductor any voltage rise on one is also a voltage rise on the other.
              I live for today, I'm just a day behind.

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                #22
                Im going to go out there tomorrow but I'm pretty sure there are no Transformers I can hook up to its all underground service there are no over head lines at all there transformer are usually under ground as well

                Sent from my SM-G965U using Tapatalk

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                  #23
                  Originally posted by nickelec View Post
                  I just spoke to one of my guys that was out there he was telling me he was getting fluctuating voltages from 112--118 phase to neutral, it was a hot day yesterday also so neighboring loads would/could make it dip even lower .
                  That doesn't give much information.

                  What was the voltage reading from phase A to phase B ?

                  voltage from A to neutral ?

                  voltage from B to neutral ?

                  Last, where was he taking the voltage measurements ?
                  The 95% of people that you can't trust give the other 5% a bad name.

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                    #24
                    I'm not sure exactly I will be heading out there tomorrow my self and will update

                    Sent from my SM-G965U using Tapatalk

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                      #25
                      190715-1031 EDT

                      nickelec:

                      What I am suggesting is go to the pole transformer pole, and you will find a wire coming down the pole that attaches to a ground rod at the pole. This is the rod I am referring to. Usually this grounding wire is covered by wood near ground level and it may not be easy to directly connect to the rod. A screwdriver poked in close to the rod will pretty well get the voltage of the rod.

                      The same applies to a pad mount transformer, but I don't know where the earthing connection is made, and/or if the pad may be the connection. A screwdriver close to the pad should be sufficient.

                      Normally there should be very little current to this pole transformer ground rod. Possibly less than a few amps. Thus, voltage drop from the transformer center tap to your screwdriver or connection should be small.

                      Your other meter lead gets connected to the neutral bus in the main panel. The voltage reading should be small, and a 10 A 120 V load should not produce much change. I am hoping for less than 1 V. If you see more than a change, either up or down, of 2 V or more, then I would suggest a neutral problem. I don't even like the 2 V criteria, but we have no information about your supply lines.

                      Without you adding a load if the voltage drop of the neutral is substantial, over 1 V, and there is no likely large load in the home, then it may indicate a neutral problem.

                      Values to use as a criteria depend on your experience, and what you see at the site.

                      ..



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                        #26
                        190715-1107 EDT

                        nickelec:

                        If everything is underground, and if you know where the transformer is, then poke the screwdriver in close to the transformer.

                        Since we have this complication, then it is possibly better to just try to use measurements at the input to the main panel. Try to put the voltmeter probes directly on the input wires. You need to have the ability to separately load each 120 V phase, and 240 phase to phase. Two 1500 W heaters will give you this capability.

                        Two voltmeters would be useful, but not necessary. The meter probes are to be directly on the incoming lines.

                        1. Read the phase A to neutral voltage change with a 10 A 120 V load added to phase A.

                        2. Same load change, but read the phase B to neutral change.

                        3. Same as 1, but now do it on phase B.

                        4. Same as 2, but load change on phase B, and voltage change on A to neutral.

                        5. Next is a 240 V loading. I would like to do a 240 V 10 A load change without any connection to neutral, but that is harder to do than just than just plugging in the two heaters.

                        6. Measure the phase A to phase B voltage, and each phase to neutral.

                        7. Load each phase to neutral simultaneously with a heater. We assume each heater is the same resistance, or at least close. Read the voltages of 6 again. This test should produce little change in the neutral current.

                        From the above measurements we should be able to learn more. Unfortunately there may be load changes from neighbors, or within the home being tested that interfere with the measurements you are making. You sort of need to make judgements on the data to filter out some of this unwanted noise to your experiment.

                        .

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                          #27
                          So I jsut left the customer and measured voltages
                          Phase a to neutral 105
                          Phase b to neutral 118
                          Phase to phase 116

                          Sent from my SM-G965U using Tapatalk

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                            #28
                            Originally posted by nickelec View Post
                            So I jsut left the customer and measured voltages
                            Phase a to neutral 105
                            Phase b to neutral 118
                            Phase to phase 116

                            Sent from my SM-G965U using Tapatalk
                            Now, what were the amperages on each phase?
                            Is 116 a typo? Should be 216?
                            Tom
                            TBLO

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                              #29
                              190718-1625 EDT

                              nickelec:

                              The voltage readings you took are next to useless in trying to determine the cause of your light dimming problem.

                              Phase to phase should be 118 + 105 = 223. The 105 seems low in comparison to the 118, but that simply could be high loading on that phase.

                              ..

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                                #30
                                Originally posted by nickelec View Post
                                So I jsut left the customer and measured voltages
                                Phase a to neutral 105
                                Phase b to neutral 118
                                Phase to phase 116

                                Sent from my SM-G965U using Tapatalk
                                Something not right with those numbers, is this 120/240 single phase or 208/120 three phase source for this?

                                208 system could read as high as 216 fairly easily phase to phase, but probably will read less if you are dragging one phase to neutral down to 105.

                                Still might be possibility of bad neutral I guess, especially if a 208/120 system. I don't see single phase 120/240 having those values, as said line to line volts should add up to 223 in that case.
                                I live for today, I'm just a day behind.

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