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  1. froggy440
    Offline

    froggy440 New EF Member

    Hey guys,

    My boss wants me terminating new supplies in a -48v d.c Distribution board. Easy enough but the board cannot be turned off due to critical load.

    Now my question is this. Is it safe and or legal to work on live -48v d.c. and what would the consequences and dangers of possible short or electrocution?

    Thanks!
    -James
     
  2. garrywatters
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    garrywatters Regular EF Member

    All I will say is "safe isolation!"
     
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  3. Wilko
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    Wilko Gorillas are Great Electrician's Arms

    Location:
    Berkshire
    Business Name:
    Wilko Electrics
    Hi - in my opinion it can be hazardous. The hazard I'm thinking about is vaporised metal caused by accidental short circuit. If the board has a low source impedance you will likely vaporise some metal if there is an accidental short. That can be very bad to be near. A proper RA should identify the risks, quantify and mitigate them. Safe isolation is the way to be, well, safe :)
     
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  4. jackhammerJIM
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    jackhammerJIM Regular EF Member

    Location:
    north yorks
    The consequence of electrocution would be a funeral followed by an investigation by health and safety .
     
  5. telectrix
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    telectrix Scouser and Proud of It Trusted Advisor

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    no danger of electrocution but as said above, a short circuit could cause a serious flash over.
    do you mean checking that the coffin was lowerewd in accordance with strict H&S guidance. no steps used in the hole, scaffold and safety harnesses used correctly, filled in using plastic spades to avoid injury?
     
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  6. davesparks
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    davesparks Trusted Advisor

    Location:
    guildford
    It can be legal, if done correctly.

    The first thing to do is explore all possible options for isolating the supply, out of hours working or a planned shutdown.

    Remember that if you do work live then the smallest slip could result in it all going off and you getting a face full of molten metal.

    If isolation is not possible then a safe system of work needs to be planned and followed. This will likely include fully insulated tools and the use of temporary insulation and barriers.
     
  7. Lucien Nunes
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    Lucien Nunes Mercury Arc Rectifier Trusted Advisor

    Location:
    London
    It's a source of energy so the same methodology and RA is required as for live work at 230V. The risk of shock is lower (although not zero) but there is an added risk of complacency from thinking that the supply isn't 'really live'.
     
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  8. Marvo
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    Marvo GMES....You absolute beauty. YOU ROCK DUDE!!!! Staff Member

    Location:
    South Africa
    Any short circuit conditions will be spectacular and can result in injury or death, shocks are possible at 48volts but unlikely to be fatal. As mentioned live work only via a risk assessment and only by persons competant.
     
  9. PEG
    Offline

    PEG Trusted Advisor

    Location:
    Manchester
    Hi,is this telecommunications or refinery,by any chance?
    I would want to know,myself,the exact details,of why safe isolation is not possible,NOT having the details second-hand,boss or whatever.

    I have had this scenario before,where the actual reason why safe isolation is allegedly "not possible",was down to the boss/clerk/contractor,not having a set of gonads,and being reticent regarding upsetting a client.
     
  10. Taylortwocities
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    Taylortwocities Electrician's Arms

    Location:
    Oxfordshire
    You might like to have a look at this little film. May put your query into context.
    Its an old BT safety film relating to exchange battery short circuits.
    I rather think they may have had fun making this.

     
    • Like Like x 6
  11. amlu
    Offline

    amlu Trusted Advisor

    Location:
    wild east london
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