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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
    And the reason for the R.C.D. tripping off when the oven is turned off is......?

    First guess would be DP switching, a high impedance N-PE fault on the oven and the DP switch happens to open N momentarily before L. Normally N is held close to 0V so little current escapes through the fault (not enough to trip the RCD), but when N is opened and L is still connected, the load's N is pulled up towards L voltage by the connected load and so a much larger current escapes - hence the RCD trips.


       - Andy.
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  • 0
    And the reason for the R.C.D. tripping off when the oven is turned off is......?

    First guess would be DP switching, a high impedance N-PE fault on the oven and the DP switch happens to open N momentarily before L. Normally N is held close to 0V so little current escapes through the fault (not enough to trip the RCD), but when N is opened and L is still connected, the load's N is pulled up towards L voltage by the connected load and so a much larger current escapes - hence the RCD trips.


       - Andy.
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