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Thread: MCB'ing individual QLD channels?

  1. #1
    Automated Home Ninja marcuslee's Avatar
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    Dec 2009
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    Default MCB'ing individual QLD channels?

    Hi Guys,

    As per the above, is the above standard practice (3A DIN rail MCB I'm thinking) for the QLD channels?

    Or has experience been that the onboard fuse on the QLD is sufficient?

    I've scanned through the docs and the forum and I don't find anything particular alluding that one should MCB each channel, but then again I'm sure in the past I'd either seen someone install their Idratek install with it, or that it was mentioned.

    I ask as we've managed to damage one of the QLD channels during commissioning and testing of the lighting circuit (even though the onboard fuse blew out).

    Any insight or advice appreciated!

    Cheers,

    Marcus

  2. #2
    Moderator Gumby's Avatar
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    I have QRIs front-ended with 2-4A MCBs, don't have QLDs, so can't speak for them.

    The Pro's
    More convenient if an MCB trips rather than a QRI fuse blows
    Provides a convenient method of isolating individual circuits to change bulbs etc (rather than a whole panel)

    The Con's
    Cost (especially as lower ratings have smaller volume and are correspondingly more expensive).
    Space
    Nuisance tripping of MCBs, especially with LV transformers with poor control over inrush (i.e. cheap ones) .. leading to using higher rated MCBs such that 'protection' of QRH/I may be insignificant.
    Cheap MCBs can hum
    Not that much discrimination, so more MCBs to inspect to get a circuit back on - not so much a problem for me, but my wife gets confused.
    ----------------------
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  3. #3
    Automated Home Ninja marcuslee's Avatar
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    Quote Originally Posted by Gumby View Post
    I have QRIs front-ended with 2-4A MCBs, don't have QLDs, so can't speak for them.

    The Pro's
    More convenient if an MCB trips rather than a QRI fuse blows
    Provides a convenient method of isolating individual circuits to change bulbs etc (rather than a whole panel)

    The Con's
    Cost (especially as lower ratings have smaller volume and are correspondingly more expensive).
    Space
    Nuisance tripping of MCBs, especially with LV transformers with poor control over inrush (i.e. cheap ones) .. leading to using higher rated MCBs such that 'protection' of QRH/I may be insignificant.
    Cheap MCBs can hum
    Not that much discrimination, so more MCBs to inspect to get a circuit back on - not so much a problem for me, but my wife gets confused.
    Thanks Gumby for insightful reply, esp the LV transformers.

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