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Here's Why an RCD on immersion is important....

  • 11-07-2009 7:25pm
    #1
    DublinDilbert
    Registered Users, Registered Users 2 Posts: 5,390 ✭✭✭


    A few months back I threw in a new distribution board in the mothers house to replace the fuse board that had been there since the late 1960's.

    After the board was replaced, when the immersion was turned on it would trip the RCD, I checked out the wiring and all look grand, so decided to disconnect and leave it for another day. It is not really used during the winter as the gas heats the water...

    Fast forward to last week, when I finally got around to taking the element out and replacing it. The old element was completely split in two over its length and the heating element was poking out and sitting in the water :eek:

    I couldn't believe the state of it (the coper cylinder was replaced about 16 years ago), see the attached pictures....

    Another win for the RCD...


Comments

  • #2
    davelerave
    Closed Accounts Posts: 1,712 ✭✭✭davelerave


    a fair percentage have to be replaced when fitting rcd protection.i think if i remember correctly that they continue to heat partially through the earth-fault loop (neutralized-no rcd)if there's a clean break in the element.so customers may assume they're working.if memory serves anyway:D


  • #3
    davelerave
    Closed Accounts Posts: 1,712 ✭✭✭davelerave


    some info here on nickel-alloy and titanium sheathed heaters
    http://www.plumbingpages.com/featurepages/HWHRtitanium.cfm


  • #4
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,602 Mod ✭✭✭✭2011


    From the ETCI:

    Q: How do RCDs work?

    A:         [SIZE=-1]Under normal conditions the current flowing in the live conductor (I L) will be the same magnitude as the current flowing in the neutral conductor (I N). The two conductors are passed through a current transformer (CT) in the RCD, and the CT will produce an output when it sees a difference in these two current magnitudes. Under a fault condition, for example a person touching a live part, an additional current (I F) will flow to earth back to the supply. Current I L will now be greater than current I N and the CT will produce an output in proportion to this differential current. If the differential current is above the predetermined trip level of the RCD, the contacts will automatically be opened thereby providing protection against electric shock.
    [/SIZE][SIZE=-1]The term "Residual" in Residual Current Device implies that there is a residual current flowing in the circuit over and above that required to provide power to a load. [/SIZE]

    stickman2.jpg


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