DC Isolator Switch

Discussion in 'The Projects Forum' started by Cerkit, Jun 25, 2012.

  1. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
    275
    3
    Hi. I am working with DC voltages in the range of 500V-1000V and so the DC isolator switches I use under the guidelines I am following need to be double pole ie there needs to be two breaks in the switch gear for every wire coming in. What I want to find out as I have been looking at various DC isolator switches is what is the difference or pros/cons between DC isolator switches which have 2 breaks per cable in series and in parallel


    So in series the break per cable is

    Code ( (Unknown Language)):
    1.  
    2. Cable ---o  o --------o   o------Cable
    3.  
    And in parallel each cable forks and there are then two poles

    Code ( (Unknown Language)):
    1.  
    2.             / ----o    o----\
    3. Cable----                     ------ Cable
    4.             \-----o   o-----/
    5.  
    6.  
    Is one more reliable than the other as far as arcing is concerned, and if so why??
    Thanks
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
    969
    What "guidelines" are you following?

    I'd suspect the requirement for a double pole switch is to disconnect both the hot and neutral with a single switch.. NOT 2 breakers per wire...
     
  3. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
    275
    3
    The guidelines are the DTI installation guides for solar pv. The switch must disconnect both the negative and positive but the requirement is for it to be double pole, so essentially the switch will consist of a total of four poles. Currently most companies use the breakers which disconnect the negative at two points and disconnect the positive at two points in the series manner as I showed in previous post. I just wanted to know if the parallel configuration is as reliable and if not why not?

    Thanks
     
    Last edited: Jun 26, 2012
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
    969
    You are interpreting the spec incorrectly.

    A double pole breaker is required to disconnect both poles via 1 single handle/switch.
    That's it..

    If you really think you are right (and I doubt it) then I would use the series method simply because of the lower installation cost (cost to "H" tap a wire versus just regular single wire terminals).. But IMO what you are saying serves NO purpose other than to increase installation costs..

    edit...
    Just found the spec.. There is NOTHING in there about having to break the wire twice. A double pole breaker is all thats required so that both the pos and neg are opened at the same time via the same handle/disconnect.
     
    Last edited: Jun 26, 2012
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