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Line and neutral in spike guard

  1. Mar 11, 2015 #1
    I have a spike guard that is showing line and neutral reversed. Those 2 Leds glow. This wasnt happening before the wiring was changed of the house.

    Now when i connect a mobile charger(with 2 pins) then the mobile gets charged,
    but when i connect a three pin hard drive power cord to it, then the hard disk doesnt work. Is there problem with the hard disk or the line n neutral reversed glow of spike guard is an indication of some other fault.

    or is there fault in the spike guard?
  2. jcsd
  3. Mar 12, 2015 #2


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    Wiring changed in the house????

    That is a red flag.

    Some speculation only: This plug may be on a switched circuit and whoever ran the return run from the switch confused himself and wired the hot return to the neutral side of the plug (one explanation).

    Or the person wired in an outlet or two without any regard to the plug polarity (the plug will work for ungrounded two prong plugs, but may cause problems with three prong devices).

    Or it could be something else. Not a hard fix, ONCE you find the problem. You should get someone to look at ASAP (ie the person who re-wired your house should fix this problem, or maybe not). I might consider using someone else.
  4. Mar 12, 2015 #3
    Thanks for the reply.

    Though my hard disk has three pin plug, i have this doubt for 2 pin plug. For 2 pin plug, why is the device not working with the line n neural reversed. In an AC circuit, phase reverses in each cycle. Current flows from Line to neutral and then from neutral to current in next cycle(negative cycle). the ground is only for safety, right?
  5. Mar 12, 2015 #4


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    Who rewired the house? Why did they do it? Did the building inspector sign off on the electrical work after it was done?

    Having line and neutral reversed is a serious safety hazard. It needs to be fixed ASAP.
  6. Mar 12, 2015 #5


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    A lot of times it is possible for things of this nature to be missed in an inspection. I am surprised that having the hot and neutral reversed would have this effect but it seems like the only likely answer. The most dangerous part of this I can think of off the top of my head is a standard lamp socket. With the hot and neutral reversed the shell of the lamp socket is now hot. Many older table lamps that are still being used do not have polarized plugs so they are being used this way already. My main concern over something like this that was missed is what ELSE was missed. Just go to: www.mikeholt.com and do some reading and some of the things discussed there will make having the hot and neutral reversed on an outlet or two seem like nothing.
  7. Mar 12, 2015 #6


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    When you say the wiring was changed, do you mean fuses were changed over to circuit breakers?
    How old is the house?
    Older homes at one time had fuses on the neutral side (before polarized plugs). Many times when the fuses are changed to breakers, the hot and neutral can get reversed.
    If you own the house, call back the person who last worked on the electric, if you rent notify your landlord to get an electrician to rectify it. This is a hazard. It needs to be fixed.
  8. Mar 13, 2015 #7
    Ugh...very sorry...

    it's not the line n neutral..but the spike guard says line n ground reversed. sorry for the error.

    the house rewired means, the plug sockets were reversed n main MCB was changed so now i have each four MCB's, one for each room. Earlier if i turned off the main MCB, then the whole house's power went off, now i can turn off power of each room by turning off corresponding individual MCB.

    About the reversal...if i plug three pin laptop plug in socket, then the laptop charges. but when i plug spike guard to socket, then the spike guard says, 'line n ground reversed.' now when i insert laptop chargers plug in the spike guard then the laptop doesnt charge.

    but a 2 pin plug works directly if inserted in the socket n it works even if i plug it in the spike guard.

    i have this basic question...since the three pin plug is not working via spike guard but the 2 pin plug is working via spike guard...then can i use loose wires, n connect one terminal of each lose wire in the spike guard n connect other ends of the lose wires to the 2 plugs of the 3 pin plug. i'll let the ground of 3 pin plug unconnected to anything.
  9. Mar 13, 2015 #8


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    I am getting lost here. Where are you at geographically? Some of the things you post are not making sense. What exactly is this spike guard? Is it an outlet strip with surge protection built in?
  10. Mar 13, 2015 #9


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    Watch these two vids:

  11. Mar 14, 2015 #10
    To me, it sounds like OP is referring to surge protection device
    But one can never be sure with OPs today (especially if English is not native language)
  12. Mar 14, 2015 #11

    jim hardy

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    jaus -

    you seem to be unsure of the spike-gard gizmo

    please invest in one of these, they're around $6US.
    Use it to check your outlets. That'll tell you whether the spike-gard is telling truth.

    you said line-gnd are reversed,
    were that so you'd be unable to touch anything plugged into the outlet and having a metal case

    most but not all of today's appliances will tolerate reversed L-N , but it's really dangerous for lamps.

    Get your house wiring squared away pronto . Tiny fingers can get hurt.
    Then we'll worry about your disk.
    old jim
  13. Mar 15, 2015 #12
    Switched phase and neutral is already a bad thing despite 99% of home electrical appliances would work. But switched phase and ground wiring is really a terrible thing. Only completely irresponsible person (read "moron") could do something like that.
  14. Mar 15, 2015 #13


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    If anyone has watched the vids I posted you will notice that one of them explains that an open neutral can cause the unit to show ground and hot reversed. I find that it is VERY unlikely that this is the case. I am wondering if this spike guard the OP is referring to is an outlet strip with surge protection built in that ALSO has an indicator built in similar to the one Jim posted in post #11. I have never used one of these testers although I have watched inspectors use them when doing final inspection on electrical jobs. I always use the low-tech sure-to-never-fail methods of: Two lead neon tester and an incandescent bulb socket with test leads. What the OP has posted just doesn't make sense. His descriptions sound just plain contradictory to me.
  15. Mar 15, 2015 #14
    A spike guard is a device for surge protection. It is an outlet strip with inbuilt surge protection and the spike guard also has indicator built just like Jim showed.

    Sorry for the error, the spike guard is showing Line and Neutral reversed. It is working for 2 prong devices but when i plug 3 prong device in the spike guard, it is not working.

    It was not showing this line n neutral reversed error before the house wiring was changed. By house wiring changed, i mean electrician came, n pulled out some wires n added new ones. a pianter had also come.

    A three pin device works when plugged to an outlet, but when i plug it to the spike guard, the spike guard shows Line n neutral reversed n the three pin device doesn't work.

    http://www.anchor-world.com/images/products/accessories/spikeguard/big/22568.jpg [Broken]it is showing 3rd fault...
    Last edited by a moderator: May 7, 2017
  16. Mar 15, 2015 #15


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    Dumb thought.... could the spike guard be defective?
    Can you get the uk equivalent of what Jim showed you in post #11?
    Until we can get good readings on the socket to be sure the problem is or isn't before the spike guard, we can only guess.
    If the socket is ok then the spike guard is probably defective. I know the timing of the problem appearing is strange, and I don't
    like coincidences, but they do happen sometimes,
    It looks like a uk version of a plug tester is about 3 pounds (I can't find the British pound symbol, sorry)
  17. Mar 15, 2015 #16
    I live in India. I googled UK spike guard images

    I'll try to post the photo of my spike guard and the error tomorrow. Maybe the problem is with the spike guard. I'll bring it to office and check it. I got plenty spike guards at office. So that should help me figure out if the spike guard is defective or not.

    HEAVY-DUTY-SPIKE-GUARD-.jpg Universal-6-Socket-Spike-Guard.jpg
  18. Mar 16, 2015 #17


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    I apologize, when I saw the configuration I thought UK. Can you get one locally where you are?
    It will really help with the troubleshooting.
  19. Mar 16, 2015 #18

    jim hardy

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    I too have a power strip but it's not so smart as your "spike guard", has only one light.
    It alerted me to a problem which the GE tester showed to be reversed L-N.
    Yours appears to have multiple lights so, perhaps it does everything my little GE tester does.

    I keep one of those testers in my toolbox. Friends often ask for help with electrical problems and it's come in handy quite often.
    Just a couple bucks more gets one with a pushbutton that tests GFCI breakers by allowing a trickle of ground current.

    For the uninitiated, reason i harp on fixing the outlet is this:

    In this US style (Edison) lamp socket
    the metal tab(s) at bottom are switched to what should be the "hot" wire L
    and the threaded barrel should be connected directly to the "neutral" wire N , with no switch in between.

    Observe that while changing a light bulb
    the threaded base makes contact with the threaded barrel long before the bulb bottoms out in the socket
    meaning your fingers will likely touch those threads while changing the bulb.
    If those threads are connected to N, no problem
    but if they're connected to L , Ouch !
    I worry about children's little hands getting disfigured .

    That's why in US lamps
    the lamp socket is wired with its threaded barrel connected to the conductor in the lampcord that's marked with a small rib

    and the ribbed conductor goes to the wider of the two prongs on the plug

    which will only fit into the wider slot in the outlet which should be N

    In my part of the country there are lots of older houses with electrical troubles.
    This link describes troubles with outdated wiring.

    observe the lamp's switch is in the wire to center button
    so if L is connected to threaded barrel, it'll shock you even when switch is OFF.

    Home handymen must be aware of these practical matters.
    Students of physics are naturally curious so will be getting their hands into electrical systems. It is good for them too.

    old jim
    Last edited by a moderator: Apr 17, 2017
  20. Mar 16, 2015 #19


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    This all confirms my love of UK electrical installation regs. :biggrin:
    You can't beat the old Blue / Brown / green yellow stripe system.
  21. Mar 16, 2015 #20
    My money is on the RE-Wiring - -- can you try the spike guard in other locations? Does it always report the same problem?
  22. Mar 16, 2015 #21


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    Reversing live and neutral sounds particularly nasty if, as I understand is common practice, you have both phases of a split phase supply feeding 'big' appliances. It takes one side of their wiring to twice what you would expect. Also, is it common to have different parts of the house wired to separate phases? If a re-wire, reversed both of them 'by mistake' it would produce exciting results!
  23. Mar 16, 2015 #22

    jim hardy

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    Hmmm i hadnt thought about that.....

    Usually the reversal happens at an outlet.
    If it happened on the incoming to the house panel, wow that could get exciting.
    Usually the incoming neutral wire is uninsulated so it's unlikely somebody would make that mistake...
    So long as the neutral is connected where it belongs there's no potential in the house greater that 120VAC wrt earth.

    Yes, half the outlets in a house are wired to one "phase" and half to the other, big appliances wired across both phases.

    What does happen a lot in my neighborhood is that one of the incoming main fuses opens. (Many old houses here still have fuses.)
    Of course half the outlets go dead. Until a big appliance is switched on, backfeeding those outlets through the big appliance. As homeowner turns on more and more lamps on that side they get dimmer and dimmer confusing him thoroughly. Usually the big appliance is his water heater , so he may see half his lights go out when fuse opens then come back on dim when water heater cools down. Maybe get brighter again when he switches stove on.
    Now THERE"s a symptom. Imagine the speculations i hear !

    old jim
  24. Mar 20, 2015 #23
    I inserted the spike guard at my workplace. it showed the same problem. So i had it repaired by the office electrician. turns out he knows more than me about power system. when i asked him 'what was wrong with the instrument?' he shrugged me away. experience teaches more than books, at times:)
  25. Mar 20, 2015 #24


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    Not surprised.
  26. Jan 12, 2016 #25
    my spike guard shows current in all 3 inlets kindly give me probable reason for that?
    How to correct it?
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