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Unusual MCB

Sparkymania
Here's an interesting one.

Federal Electric 20A MCB. Had no type on it and was taking a long time to trip. Opened one up and discovered why it didn't have a type.

Others with it were ECC but virtually the same design. Only thermal. Both are plug in types called stab-lok and are bakerlite.


No instantaneous trip mechanism. Only a thermal one.



34200b5e07a12e120f5fc679b8b1b9aa-huge-mcb-with-no-instantanious-trip-mechanism-4.jpg
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  • 0
    A good steer from Chris.


    They are BS 3871 MCBs.

    White handles are Type 1.

    Green handles are Type 2.

    Orange handles are Type 3.

    Black handles are Type 4.


    They are known to be problematic. Just putting you finger tip on a single breaker will reveal a lot of wobbeling around between the MCB and the bus bar. I have see a few occasions where there has been a flash over on the bus bar which has caused upstream protection to operate. On one occasion it took out 2 services fuses. 


    If I see them I recommend a board change.


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  • 0
    A good steer from Chris.


    They are BS 3871 MCBs.

    White handles are Type 1.

    Green handles are Type 2.

    Orange handles are Type 3.

    Black handles are Type 4.


    They are known to be problematic. Just putting you finger tip on a single breaker will reveal a lot of wobbeling around between the MCB and the bus bar. I have see a few occasions where there has been a flash over on the bus bar which has caused upstream protection to operate. On one occasion it took out 2 services fuses. 


    If I see them I recommend a board change.


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