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Separate Switch Disconnector enclosure

fiftyhertz
Morning All, 


Why would you use a separate switch disconnector enclosure ie Schneider SEA9PNI2504, the vast majority of distriubtion boards i see have an incomer device at the base of the busbar, which could also be used as a protective device. Never really understood why a separate unit would be required?


Is there a practical reason im missing.


Thanks
  • 0
    Sometimes isolation is wanted in other places as well as the DB - e.g. local to equipment or at the origin of the installation so downstream DBs could be completely isolated for maintenance or replacement or perhaps before some other means of distribution - such as a bus-bar chamber.

       - Andy.
  • 0
    A common isolation for the supply to a bus-bar chamber feeding many boards or with multiple supplies maybe ?

    I agree at the price they are you won't be putting them in for fun.
  • 0
    The practical reason is that the 250A switch is too big so requires a separate enclosure. The standard Acti9 boards, although the busbar is rated at 250A, only have the physical capability to have a 125A 4P switch in the conventional position. So when you need more capacity you have to fit the separate extension enclosure. It has all the links to join it to the busbars in the kit of that number you mentioned Fiftyhertz
  • 0
    Modern distribution boards often do a superb job in shielding live parts, including those associated with the incoming device. However, in certain quarters even with such shielding, the risk is not mitigated to an acceptable level and they require the complete assembly to be safely isolated before accessing for maintenance. Making off a swa in to a distribution board could have those long bare wires contact the supply terminals even though the tunnels are fairly small. I know, for it happened to one of my guys, luckily without injury!
  • 0
    Dbat:

    The practical reason is that the 250A switch is too big so requires a separate enclosure. The standard Acti9 boards, although the busbar is rated at 250A, only have the physical capability to have a 125A 4P switch in the conventional position. So when you need more capacity you have to fit the separate extension enclosure. It has all the links to join it to the busbars in the kit of that number you mentioned Fiftyhertz


    Thanks Dbat, after re-reviewing the data sheets it appears you are correct. Anything above 125A needs a seperate disconnector mounted to the base of the unit.


    Thanks all


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