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General Chat Thread, Question about electrical supply in General; An RCD effectively measures the current in the live and neutral of the supply and if they differ by more ...
  1. #16

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    An RCD effectively measures the current in the live and neutral of the supply and if they differ by more than the rating of the RCD then it trips. RCD's ratings are in milli Amps (mA) rather than Amps. I've seen several causes to the trips being a little keen:
    • The trip is aging and is tripping at a lower level than the rating.
    • The devices plugged are heavily filtering the mains.
    • The mains is 'dirty' and the filters in the supplies are just doing their job to keep the devices safe.

    The cure is to get the electricians back in to test the RCD is at its specification and all the devices plugged in do not have leaky PSU's. If these show up as good then it is possible to get a monitor installed to check to see what condition the mains is in, does the supply voltage vary, does it have any spikes, etc. If all else fails it may be necessary to replace the RCD with one with a slightly higher rating simply because you have too many devices filtering just a little too much when combined together.

  2. Thanks to sjatkn from:

    Little-Miss (23rd August 2012)

  3. #17

    SimpleSi's Avatar
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    When I was liitle, you only needed RCDs to feed electricty to certain areas (like outside or anywhere where water was present)

    Have things changed?

    If not, get the RCD dumped and just put in straight forward MCB (minature circuit breaker) as that will be very cost effective

    The other problem can be that lets say your kit takes 30 amps and breaker is 32amps so your on the edge but get away with it until some little event occurs (mains dip followed by 40A surge for instance)

    Simon

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    Little-Miss (23rd August 2012)

  5. #18

    twin--turbo's Avatar
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    Quote Originally Posted by SimpleSi View Post
    When I was liitle, you only needed RCDs to feed electricty to certain areas (like outside or anywhere where water was present)

    Have things changed?

    If not, get the RCD dumped and just put in straight forward MCB (minature circuit breaker) as that will be very cost effective

    The other problem can be that lets say your kit takes 30 amps and breaker is 32amps so your on the edge but get away with it until some little event occurs (mains dip followed by 40A surge for instance)

    Simon
    We are just on MCB's for the server room to avoid issues with RCD losses.

    In our old building we had a room on RCD's that tripped every morning until we had the RCD's replaced with less sensetive ones.

    Rob

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    Ok here's a daft one. The little box which houses the RCD for the room is next to the bigger box with different areas of the school. I'm guessing there was no more physical space in the big box, hence having its own. But new cables would've been run as like I said this area didn't have electricity before. Sound about right? So run from old box, new cabling.

    Another thing that's just dawned on me is my mahussive new sparkling master cab, which is also up with me has its own separate power supply which is connected to the main fuse board (I suck at the terminology) . Lol would it be bad practice to run my ups/servers from that.....
    Last edited by Little-Miss; 23rd August 2012 at 11:38 AM.

  7. #20

    twin--turbo's Avatar
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    You realy need to know what the circuits are and where else they feed.

    If someone trips the mains in a room halfway down the corridor you don't want it to be the same circuit that your cab is on.


    Rob



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