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M.E.M. R.C.D. Tripping Off.

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Mornin' All,

                      on this mild still spring type morn.

Do you remember the M.E.M. type R.C.D. that had a three position switch?


TOP POSITION = ON,


MID POSITION = TRIPPED.       LOWEST POSITION = PUSH SWITCH DOWN FROM MID POSITION BEFORE PUSHING TO TOP POSITION TO RESET TO ON.


Many months back I had a problem that when the customer turned her oven OFF it tripped the R.C.D. to OFF. (Read that carefully).


A new R.C.D. seemed to solve the problem.


Last week I came across exactly the same problem. Now that  a new R.C.B.O. consumer unit has been installed all is o.k.


Any ideas as to why this situation exists?


Z.


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  • 0
    Alan Capon:

    Following on from BOD, it also means that the Device cannot be immediately reclosed, without the deliberate action of moving the operating lever to the “Off” position first. There are (were) a few other manufacturers that used the same method. 


    There is also an interesting issue with RCBOs on TT. If you fit a 10 way RCBO with an ordinary main switch, worst case, you can have up to 300mA of leakage before you get a trip. Your earth needs to be good enough for this, but ideally you want a time delayed main switch, especially if the RCBOs are single pole switching. 


    Regards,


    Alan. 


    Ideally upfront 100mA time delay RCD and then DP RCBO’s 


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  • 0
    Alan Capon:

    Following on from BOD, it also means that the Device cannot be immediately reclosed, without the deliberate action of moving the operating lever to the “Off” position first. There are (were) a few other manufacturers that used the same method. 


    There is also an interesting issue with RCBOs on TT. If you fit a 10 way RCBO with an ordinary main switch, worst case, you can have up to 300mA of leakage before you get a trip. Your earth needs to be good enough for this, but ideally you want a time delayed main switch, especially if the RCBOs are single pole switching. 


    Regards,


    Alan. 


    Ideally upfront 100mA time delay RCD and then DP RCBO’s 


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