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Neutral fault damaged several PSU - Is it possible ?

Discussion in 'Electronic Repair' started by JC, Sep 18, 2012.

  1. JC

    JC Guest

    Hi !

    After some repairing at my house an electrician made an error and didn't connect a neutral on a circuit breaker that was sourcing some electronic equipment I have (router, switch, alarm).

    The repair work was done on Friday and on Sunday, when I tried to access the network I found out that all the electronic equipment was damaged and notfiring up (the PSU I suppose).

    At first sight, it seems that if the neutral is not connected we wouldn't have a diff of potential so I don't see how the equipment could be damaged but live & earth were ok so I wonder if anyone can explain to me if the lackof neutral could have been the cause.

    Thanks/Brgds
    J
     
  2. Phil Allison

    Phil Allison Guest

    "JC"

    After some repairing at my house an electrician made an error and didn't
    connect a neutral on a circuit breaker that was sourcing some electronic
    equipment I have (router, switch, alarm).

    The repair work was done on Friday and on Sunday, when I tried to access the
    network I found out that all the electronic equipment was damaged and not
    firing up (the PSU I suppose).

    At first sight, it seems that if the neutral is not connected we wouldn't
    have a diff of potential so I don't see how the equipment could be damaged
    but live & earth were ok so I wonder if anyone can explain to me if the lack
    of neutral could have been the cause.


    ** A disconnected neutral would normally result in no AC power on that
    circuit as the earth conductor is not used for carrying load current.

    Only if the neutral conductor were common to more than one phase can a
    damaging over voltage exist. This may sometimes be the case in the USA, but
    is not permitted in 240 volt countries for domestic installations.


    .... Phil
     
  3. Den 19-09-2012 00:12, Phil Allison skrev:
    If the neutral wire in the feeder gets disconnected then you will have
    random voltages anywhere in the installation.
    Voltage will be anywhere between normal line voltage 115V in US or 230V
    here in DK and (sqrt3 * line voltage)
    US: sqrt3 * 115 = 200V
    DK: sqrt3 * 230 = 400V
     
  4. Phil Allison

    Phil Allison Guest

    "Uffe Bærentsen"
    Phil Allison skrev:
    ** Clearly NOT the OP's question.


    then you will have
    ** In the USA, 120V domestic circuits are fed via a split phase transformer
    from a 3 phase, 240V street supply.

    Most homes have 240V and 120V power available, the 240V being used for high
    consumption appliances.

    The 240v is really 120V-0-120V - so a loss of the incoming neutral can
    case the supply to go to 240V.


    ..... Phil
     
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