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Thread: Genset connection as per SANS 10142-1 Figure S.4

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    Genset connection as per SANS 10142-1 Figure S.4

    Hi,

    I am designing a new DB to connect a three phase genset to my existing single phase household DB. The genset has the capacity to service all the plug and light circuits. So I will not have an essential circuit section. The two DBs are about 15m apart.

    My question is as follows:

    Due to the fact that the existing DB is about 22 years old and too small, I will replace this with a new one as well, splitting the high current circuits onto a non-essential circuits DIN rail. The idea is to install a new second DIN rail that will host three groups of plugs and light C/Bs (balanced L1, L2 and L3). The new DB will also feed plugs and lights in my new workshop on (L1 - L3). My idea is to install three single phase E/Ls in the new DB, one for each group of C/B's in the new and old DB's while using the existing EL in the existing DB for the non-essential high current circuits located there. I have installed an automatic 63A cross-over switch (3 pole on the single phase side, mechanical interlock, three pole + auxillary (neutral) on the 3-phase genset side). The cross-over switch is PLC controlled and will engage only when the genset is on operating temperature. In Figures S.2 and S.4 an E/L from the genset is indicated to be located before the change-over switch. My idea is to locate the 4 off E/Ls after the cross-over switch.

    I would appreciate feedback on this design. I can provide a drawing if so required.

    Thanks

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    Hi. Reason why in in figure S.2 and S.4 E/L is before the change over switch is so that when your normal muncipal/eskom supply is on that you do not have 2 ELCB in series and when your geny is on that there still is Earth leakage protection.

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    @Eskom I understand that, but in my case I see no reason not to move the E/L to after the change-over switch as the DB will simply have two sources of power (grid or genset and maybe in future an inverter) that gets switched into a single source leading into both DBs.

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    It seems relying on the arrangement in S.1 is more appropriate to what you aim to achieve.

    I appreciate that refers to an e/l device (singular), but it would seem ridiculous that the intent was to force a single unit for earth leakage protection approach...

    Also to note in the arrangement you're proposing, you'll have to take care navigating the Main DB and Point(s) of Control issues that could arise.
    The trouble with opportunity is it normally comes dressed up as work.

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    Quote Originally Posted by mygoggie View Post
    ........I have installed an automatic 63A cross-over switch (3 pole on the single phase side, mechanical interlock, three pole + auxillary (neutral) on the 3-phase genset side).
    Is the auxiliary designed to make/break the load current? I'd check the spec carefully to make sure the aux contact makes and breaks simultaneously with the other contacts.

    I've attached the drawings S1-S4 for anyone trying to follow this that doesn't have them at hand.

    Emg Power Config.pdf
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    Quote Originally Posted by AndyD View Post
    Is the auxiliary designed to make/break the load current?
    Good point, I will double check on this as I am now concerned that the EATON Aux contacts cannot handle 65A. As far as I know the regs (and commons sense), the contactor (aux in this case) for the neutral must be the same current rating as the L1-L3 ratings. Correct me if I am wrong.

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    Quote Originally Posted by Dave A View Post
    It seems relying on the arrangement in S.1 is more appropriate to what you aim to achieve.

    I appreciate that refers to an e/l device (singular), but it would seem ridiculous that the intent was to force a single unit for earth leakage protection approach...

    Also to note in the arrangement you're proposing, you'll have to take care navigating the Main DB and Point(s) of Control issues that could arise.
    @DaveA - Yes, you are 100% correct - S.1 is the more appropriate layout.

    Kindly explain to me what you mean by "Main DB and Point(s) of Control issues".

  8. Thanks given for this post:

    IanF (16-Sep-15)

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    Quote Originally Posted by mygoggie View Post
    Good point, I will double check on this as I am now concerned that the EATON Aux contacts cannot handle 65A. As far as I know the regs (and commons sense), the contactor (aux in this case) for the neutral must be the same current rating as the L1-L3 ratings. Correct me if I am wrong.
    Yes, essentially you need a 4-pole changeover switch, not a 3-pole with an aux contact. Whilst the neutral current may be low if it's a balanced load across the 3 phases the neutral contact must still be able to make and break the worst possible case load. Also if the neutral contact is late make or early break there will be a large voltage spike during changeover.
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    Quote Originally Posted by mygoggie View Post
    Kindly explain to me what you mean by "Main DB and Point(s) of Control issues".
    Two supplies and 2 DBs some distance apart... we've come across some nightmares where just which is the main db and just what it'll take to de-energise the entire installation is pretty obscure.
    The trouble with opportunity is it normally comes dressed up as work.

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    Quote Originally Posted by Dave A View Post
    Two supplies and 2 DBs some distance apart... we've come across some nightmares where just which is the main db and just what it'll take to de-energise the entire installation is pretty obscure.
    OK, now I understand. Thanks. I think a sketch is now required to explain the layout and to make advice giving easier!

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