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Thread: voltage drop

  1. #16
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by Reach4 View Post
    Now you are just trolling. You know that is not true.

    That may be true if JW calls 1 Volt a big difference. But that is about normal, at a outlet on a long wire run drawing 10 amps.

    The difference in ground and neutral, is the Voltage drop on the neutral wire feeding the outlet.

    There should not be a big voltage difference at the breaker panel, If so the feeder wire is to small, or the panel is not bonded properly.


    I doubled with you JW, You did not say "Over" , my mistake, but what you say is true.

    Over
    Last edited by DonL; 01-24-2014 at 04:13 PM.
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  2. #17
    DIY Senior Member Reach4's Avatar
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    Edit: paragraph withdrawn.

    At each house there is normally a ground rod or two that is electrically connected to the incoming neutral conductor. 2. True? 3. Are those ground or neutral rods? In side the first breaker box, the neutral terminal and "ground" terminal strips are connected electrically together inside the breaker box. 4. True? . We understand that is not the case in a sub-panel.

    I know none of those things come as a surprise to you.

    Edit: I just figured out that when you said "big difference" (even on a thread with Voltage in the subject) you meant "big distinction". Green vs white is a difference too, but in the voltage world, I see 2 volts as a difference.
    And jadnashua, care two answer the first 3 questions?

    The Kirchhoff's current law review -- you do have only power 1 wire coming to your neighborhood, right?

    And here is an extra question if you want to respond jadnashua: 5. If there had been a proper grounding/neutralling/wtf system in place at the house, but the neutral wire on the drop was broken, would that symptom the OP saw have been observed? At least 2 flaws here IMO. Power company first. Then maybe more.
    Last edited by Reach4; 01-24-2014 at 08:46 PM.

  3. #18
    Retired Defense Industry Engineer jadnashua's Avatar
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    The only time the ground wire/rod should ever carry current is if there is an induced voltage as from a lightning strike or a fault in the system...IOW, the ground lead should NEVER have current running through it except in exceptional circumstances. Power needs a complete circuit and that's from the hot lead to either the other side of the transformer directly (in a typical 240vac residential system), or via the neutral lead, which still gets to the other side of the transformer, but not passing through ground.
    Jim DeBruycker
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  4. #19
    DIY Senior Member bluebinky's Avatar
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    Quote Originally Posted by jwelectric View Post
    The neutral is the center tap of a transformer but grounding is the connection to earth in an ungrounded system there will be no neutral from the utility but there will always be an earth connection or grounding if one pleases.

    It is very true that the utility connects their earth ground to the neutral just as we do at the service equipment but the neutral is a current carrying conductor and the grounding is not current carrying a very huge difference.
    I agree with JW on this one. Also, agree about shutting off the main breaker until the problem is fixed.

    I have a silly question. Are there any main breaker panels that can be configured as a sub-panel -- by removing a bonding screw?

  5. #20
    DIY Senior Member Reach4's Avatar
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    It looks like I was wrong about the distribution transformer grounds; it seems they have separate ground rods and wires for the high and low voltage sides. I wonder if it has been like that forever or if that practice started after sharing grounds for years. Anyway, here is the schematic using separate grounding rods: I still think the OP's system has at least two problems.

  6. #21
    Electrical Contractor/Instructor jwelectric's Avatar
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    The use of earth return path on utility power is a dying thing simply due to the resistance of earth.

    Earth return is never used on the house side of a transformer. Ohmís law can be used to figure out a lot of the reasons why. The NEC mandates that we can use one rod for an electrode only if that one rod has 25 ohms or less of resistance to earth. Using this 25 ohms as the resistance and Ohmís Law of voltage equals the current times the resistance we can see that 120 volts divided by 25 ohms of resistance will equate to only 4.8 amps of current flow.

    One might ask why I didnít use 240 volts instead of 120 volts and the answer lies in what would happen should one touch two 120 volt conductors together. It would be impossible to connect 240 volts to a ground rod from a residential panel but even if one could it would equate to only 9.6 amps of current.

    Most not all residential transformers across America is fed by 7200 volts and at this voltage only 288 amps of current could flow.

    The wires on the highest part of the pole holding the transformer are the high voltage lines. There will in most cases be one, two, or three up top and one a little lower down the pole. The one that is lowest down is the utility neutral.

    Looking up at the transformer we will be able to see that one of the higher wires is connected to a fuse then from the fuse to the transformer. This is the supply voltage for the primary of the transformer.
    In most cases there will be three wires coming from the side of the can that supplies our homes, this is the secondary of the transformer.
    Notice that the bare conductor is connected to the lug in the center, the house neutral or the center tap of the secondary. From this center tap we can also see a #6 hard drawn conductor that runs down the side to the utility pole and disappears into earth. This tap may not be right at the center tap lug but it will be on that neutral conductor somewhere up there. Now pay close attention to that lower conductor on the utility side of the transformer. Can you see that that bottom conductor is also connected to that #6 that is coming down the side of the pole. Yes the high voltage neutral, the low voltage neutral and the grounding electrode are tied together on the top of that pole.

    A lightning event is an event between earth and a cloud. The utility wires are hanging somewhere in the area between the cloud and earth. Should the path of the lightning arc include those wires hanging up there in the air then giving that lightning an easy path to find earth is the sole purpose of the earth connection by both the utility and the electrician. The earth connection by either the utility or the electrician plays no role in the use of current in our homes. What makes our homes safe is the bonding of the grounding conductor to the neutral at our service equipment which give a low impedance path for fault current to find its way back to the center tap of the transformer.

    The ORIGINAL POSTER has a problem with this center tap conductor. Instead of having two parallel 120 volt paths for current to flow he has one 240 volt series path for current to flow.

    Using the air conditioner disconnect we can wire two keyless in series from one terminal to the first keyless then to the second keyless back to the other terminal of the AC disconnect. We have a 240 volt series circuit with on neutral. Put two 100 watt bulbs in those two keyless and turn on the disconnect. Both lights come on and will have a voltage of 120 volts at each keyless, no neutral.
    Now change on of the 100 watt bulbs with a 40 watt bulb and turn on the disconnect. The 40 watt bulb will be burning brighter than the 100 watt bulb and the voltages on the two bulbs will be greatly different. This is what is happening with the ORIGINAL POSTERER.

  7. #22
    DIY Senior Member Rich B's Avatar
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    I repaired a 5000 watt Generac generator yesterday. Owner never said what was wrong with it so I had to check it over for myself.
    After fixing the carburetor, starting it and running it and checking all the outlets I found normal 240 volts at the 240 twist lock......low voltage at the 120....and also low voltage from the hot side of the 120 outlet to frame ground...

    I disconnected to output leads from the generator end.....a 3 lead configuration just like a house.....Voltage was good.....240 L-L and 120 L1 -N and L2 -N . Many generators I work on are 4 wire......2 windings and can be tapped for 120/240 or 120 only. A 3 wire is one winding with a center tap for the lower voltage. They usually are not bonded frame to neutral......4 wire units that I work on most are bonded...neutral to frame ground....Onan RV units.....

    Disassemble the outlet panel and the neutral connection is disconnected.......machine does not have frame bonded to neutral....so you will not see a 120 from either L1 or L2 to frame ground.....

    What does this have to do with the OP'ers problem......His problem is the neutral and it is just a matter of either it is a connection issue at his Service Entrance or meter pan or something further back to the pole. I doubt it is a transformer myself.......I would bet it is a bad splice connection. The service is the homeowners responsibility up to the connection point from the power company........

    JW's description of the power on the pole is spot on.....Anywhere there is a transformer on a pole they drive a ground rod but it has nothing to do with the neutral.....it is just like at your house......a path for high voltage like a lightning strike or surge....

    Anytime I lose power the first thing I do is walk across the road and take a look up at the fuse holder on the transformer that is there for my service drop. Had a storm a few years ago and lost power.....fuse holder was blown apart and I heard the strike clear as can be......The fuse is on the primary side.....NO fuse on the secondary side......and there is plenty of power available there....even though it is only 240 volts L to L....
    Last edited by Rich B; 01-25-2014 at 09:58 AM.

  8. #23
    DIY Senior Member Reach4's Avatar
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    Quote Originally Posted by jwelectric View Post
    The NEC mandates that we can use one rod for an electrode only if that one rod has 25 ohms or less of resistance to earth. Using this 25 ohms as the resistance and Ohm’s Law of voltage equals the current times the resistance we can see that 120 volts divided by 25 ohms of resistance will equate to only 4.8 amps of current flow.
    Very good point. I concede that there may only be the one fault.

  9. #24
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by Reach4 View Post
    It looks like I was wrong about the distribution transformer grounds; it seems they have separate ground rods and wires for the high and low voltage sides. I wonder if it has been like that forever or if that practice started after sharing grounds for years. Anyway, here is the schematic using separate grounding rods: I still think the OP's system has at least two problems.

    Looks to me like this would be 240V/480V.

    Around here it is 120V/240V. And the Grounds are connected together.

    That was a nice post JW.

    I like your Idea of using light bulbs for testing. Too bad they are getting harder to get.

    In your example the 40 watt bulb may not last to long. Same goes for the Appliances in the OPs house.


    I would hope the problem has been fixed by now.
    Last edited by DonL; 01-25-2014 at 06:30 PM.
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  10. #25
    DIY Senior Member Rich B's Avatar
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    I have never seen anything that was 240/480 and it does appear to be showing that in the drawing.....

    No such thing around here......anyway...

    480 is common but is 277/480 and also

    120/208 or 120/240 ......and all are 3 phase usually in commercial buildings...

    Residential Service power is either 240 or 208 and single phase....

  11. #26
    Electrical Contractor/Instructor jwelectric's Avatar
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    This is typical of Wikipedia type of information. Mostly wrong and uninformed and the very reason why colleges and universities will not accept information form Wikipedia.

    What we have to remember is that the information found there might be coming from Japan, Korea, China, or anywhere else anyone has a computer and the ability to get on the internet. The information found there is easily edited by anyone although this type of system is pretty common across the blue fish pond.

    Our neighbors north of our border are changing all their earth return systems due to the effect it has on livestock and wildlife. Four legged animals don’t seem to fair to well with this type system.

    I have an electric fence that encloses my pastures that contain our horses. During rainy times there are certain spots in the pasture the horses will not go due to the current they feel through their feet.
    Last week during the rain my grandson threw out a couple bales of hay and was amazed that the horses would not eat the hay. I turned off the fence and the hay disappeared in one day. Through the frog of a horses hoof is what tells them to grow their winter coat and to shed it in the spring. It is very sensitive and just a little current will affect their moods. The same is true with just about all four legged animals. A cow or goat will stop producing milk when subjected to ground currents. This is the reason for the requirement for the bonding grid found in Article 547 of the NEC

  12. #27
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by jwelectric View Post
    This is typical of Wikipedia type of information. Mostly wrong and uninformed and the very reason why colleges and universities will not accept information form Wikipedia.

    What we have to remember is that the information found there might be coming from Japan, Korea, China, or anywhere else anyone has a computer and the ability to get on the internet. The information found there is easily edited by anyone although this type of system is pretty common across the blue fish pond.

    Our neighbors north of our border are changing all their earth return systems due to the effect it has on livestock and wildlife. Four legged animals don’t seem to fair to well with this type system.

    I have an electric fence that encloses my pastures that contain our horses. During rainy times there are certain spots in the pasture the horses will not go due to the current they feel through their feet.
    Last week during the rain my grandson threw out a couple bales of hay and was amazed that the horses would not eat the hay. I turned off the fence and the hay disappeared in one day. Through the frog of a horses hoof is what tells them to grow their winter coat and to shed it in the spring. It is very sensitive and just a little current will affect their moods. The same is true with just about all four legged animals. A cow or goat will stop producing milk when subjected to ground currents. This is the reason for the requirement for the bonding grid found in Article 547 of the NEC

    I think that is one reason that you can find night crawlers around light poles. Makes for good fishing.

    It is great to be a old fart, I do not care what people say. Live and learn.


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  13. #28
    DIY Senior Member houptee's Avatar
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    Grounding problems on utility pole lead to death of a cable television technician.

    http://ecmweb.com/shock-amp-electroc...ng-ground-wire

  14. #29
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by houptee View Post
    Grounding problems on utility pole lead to death of a cable television technician.

    http://ecmweb.com/shock-amp-electroc...ng-ground-wire

    That is a bit scary.

    I wonder if that was a new technician, that cut the ground wire, trying to repair a Ground Loop problem.
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  15. #30
    DIY Senior Member Rich B's Avatar
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    I drove home from work about 3-4 years ago and as I pulled into my driveway I noticed some wires hanging down from the pole that services my home. I have had TV cable wires cut and dropped before and they are on the same side of the house as my service. Trucks passing on my side of the road and going slowly because they are not sure where they are going move as far as they can to the area where the cables hang lowest. This time someone caught and severed my service cables. The service was still intact on my house. The anchor was still there and somehow held.......the cables were severed and lay in the street along the curb near the pole. I carefully took a look to see if the primary fuse was ok....it was so I assumed the cables were live.....they were..

    I called 911 and explained the situation.....Lots of people walk down that side of the road including kids.....The 911 person, a man, asked me why was I calling them and that they were very busy......Nice response! I told him how dangerous this was and luckily he took me seriously. The town fire official showed up and soon a police car. We monitored the cable and made sure no one came in contact with it.......power company showed up and spliced the cables back together. I did not think they would do this as the service cable head needed to be re-attached. I called an electrician and had a new service mast installed......The one there was pretty old and the meter pan had problems a few years earlier....

    This is the third time I warned someone about something that was dangerous with power lines near my home and it amazes me that they look at me like I am overstating the danger.....and this is just the low voltage side of the power but there's plenty of power there.......I passed a spot one day jogging and could see the same thing happened along a major road. The cables must have been severed by a truck and the live cables danced around on the ground. It left carbon tracks so you could clearly see where it was.....There was black glass there where it had burned hot enough to turn cement to glass.........I picked some up and saved it......

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