Motor start makes lights brighten.

Discussion in 'General Electronics Chat' started by #12, Mar 3, 2012.

  1. #12

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    I have what I consider a very strange situation at my house. Whenever a 120V motor starts, like the refrigerator compressor or garbage disposer, the ceiling lights get noticably brighter during the starting surge. They might be a bit brighter all the while the motor runs, but not enough to register with my eyes. I have been all through the breaker box tightening all the connections, and I'm no amateur at this.

    I wonder...could an inductive load be correcting the power factor on the local power lines?
    Could this be about the fact that this is the dry season and the sand (earth grounds) hasn't been properly wet for months?
    Could this indicate a fault in the power lines to my house?

    Just for information, American residential power is 240V split phase. Two legs, (theoretically) 180 degrees apart with a neutral at earth potential that can be used for 120 volt loads.
     
  2. crutschow

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    Mar 14, 2008
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    Do yo have a meter that you can use to monitor the AC voltage?
     
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  3. #12

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    Yes. I have a very nice Fluke with 1% guarantee, but nothing to measure phase unless I set up some sort of way to use my dual channel scope to do that.

    I say this because I am very open to suggestions, and measuring is a great way to find the truth.

    ps, I started out expecting a faulty ground but examination has found no loose connections or corrosion.
     
  4. jimkeith

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    Oct 26, 2011
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    You have a corroded neutral connection to your house--when one side of the split phase is suddenly loaded, its voltage decreases, but the other side of the split phase increases. I have seen this numerous times--the aluminum neutral line is subject to corrosion at the meter or at the bugged attachment point to the house.

    I also had one case where the plastic cable jacket trapped water where it passed through the wall of the house to the breaker panel--where water was trapped, the aluminum corroded to almost nothing.

    Could also be the power companies problem at the pole...
     
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  5. #12

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    In answer to crutschow...the voltage in the kitchen receptical is 122.6 until I turn on the garbage disposer. Then the Max capture of my Fluke sees 132.4 V. As soon as the start surge is over, the line settles at 126.0 volts. (3.4 volts higher than without the motor running).

    I shall now go outside the house and investigate the grounds.

    (Thanks to you both.)
     
  6. #12

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    Bingo.

    The aluminum clamp on the copper water pipe had loosened by more than 2 turns on each screw. It was actually floppy. After only tightening it, the surge increase was only 2 volts. 80% improvement. Proper cleaning and tightening should fix this completely.
     
  7. jimkeith

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    Not good--this means that your neutral connection is relying upon the safety ground through your plumbing--boo!

    Makes the earthworms squirm...

    Also had a disagreement with a lineman that came to fix a flickering lights complaint--he said that the bugs were good--when asked why he thought so, he said because they will not pull out and proceeded to show me how he pulled on the connections with an insulated pole--I insisted that he replace the neutral connection which he did. Upon inspecting the removed bug, it was obviously loose, but would not pull out.
     
    Last edited: Mar 3, 2012
  8. #12

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    I'm having a bit of trouble with your use of the word, "bug". Do you mean, "clamp"?

    The power company employees here are neither smart nor dedicated. I take it you suggest I should bother them about getting a proper neutral wire to my house?

    After cleaning up the connection, I get 1.4 volts elevation during the start surge of a 1/2 horse garbage disposer, and the running voltage is elevated by .2 volts. Not enough to annoy me. Still wondering of the drought conditions in a state made of sand is interefering with...no that's not right. The 2 phases and neutral are hard wired at the transformer. Earth conductivity should not have any thing to do (carry current) if the hard wiring is proper. Right?

    Ps, we don't have earthworms here. We have nematodes. Nasty little worm looking things that eat the roots of plants, thus limiting the number of species that can survive here. Imagine, pulling up a carrot and finding worm holes in it! I say, "let 'em squirm" but I can also see that a crusty neutral is a problem on its way to getting severe.

    Thanks a lot. It didn't occur to me that the phases would become un-centered because of a single phase load and a crusty neutral wire. I guess that's what AAC is about...ppl helping each other with knowledge honed in their specialty. Precision analog experience is about useless with power distribution grids.
     
  9. jimkeith

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    Simply a large crimp connection--a lineman would probably use or understand this term.

    Yes, you may have to get the power company involved after you have exhausted everything after the meter.
     
  10. #12

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    I finished nailing down the culprit this morning. Put an amp-clamp on the wire to the water pipe, turned on a toaster oven and measured 11 amps going through the dirt ground.

    My nephew came over about 1 pm and I went to demonstrate this to him. Not a twitch on the meter! Well, it's a very windy day, so I figure the flopping of the wires from the pole to the house rubbed the connection clean...for a while. Good thing I decided to put off whining to the electric company until Monday. It will go bad again in a few days or weeks, then I'll call them.
     
  11. maxpower097

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    Nematodes actually help plant roots by eating other bugs that attack the roots. For instance modern corn has bread out the signal call to attract nematodes when they are under attack. They did a study with modern GMO corn and old heirloom corn. Planted 3 of each and had a tube leading to the center of all of them. The then innoculated the corn with a root eating bug plaguing our corn crops. Then they injected nematodes in the center of the plants. Then Non GMO heirlooms put out a chemical signal and all the nematode raced to the plants and killed the predator insects. The New GMO corn was unable to put out the signal and died off from the bugs. They also sell them at the garden center as a beneficial insect.
     
  12. n1ist

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    Mar 8, 2009
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    Call them immediately. If that neutral opens again, everything grounded in your house will rise above ground potential. This is a fire and electocution hazard. If the connection to your water pipe would open, all electonics in your house would likely be destroyed as your phase voltage will wander based on per-phase load.

    Once again, don't play around when you have a neutral problem.

    /mike
     
  13. jimkeith

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    Yes, if the load is not balanced (and it does not have to be balanced at all) and your safety ground fails, something(s) will go up in smoke, not to speak of the potential shock hazard...
     
  14. #12

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    I went outside this morning and finished getting a big enough screwdriver on the clamp to the water pipe. Loosen, tighten, wiggle wiggle. Got rid of that half ohm of resistance. Went inside and a 6 outlet strip (with MOV's) was smoking. Phoned the electric company. A man came out. I showed him the smoking guts and told him my measurements. He used something like a megger on the wires, found nothing wrong, and drove away.

    He said it might have been a tree brushing against the lines causing 11 amps of current to go through the water pipes and cause the MOVs to pop.

    Did I say something in post #8 about, "neither smart nor dedicated"?

    I guess I'll put a redundant cable from the neutral/bond in the mains box to the nearby water pipes in the laundry room. I can't make the power company put new crimp connectors on my neutral line but I can put a redundant bond wire on the breaker box.
     
  15. jimkeith

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    Time to go over his head--the hinge that squeaks loudest is the one that gets oiled...
     
  16. #12

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    I believe you're right.
     
  17. n1ist

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    Don't disconnect your existing ground; it's all that is protecting your electronics. Definitely don't do this without the proper protective equipment or you can get killed.

    Adding a second ground clamp is NOT a safe solution. You need to call the power company and report an open neutral with lights getting brighter; if they don't respond, try the fire department and your town's public utilities person. Don't tell them about any measurements or work that you have done, just tell them about the lights and burned power strip.

    You have already smoked a power strip; is it worth burning down your house or killing yourself (or a plumber)?
     
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