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Fake circuit breakers

broadgage
Seem to be on the increase.

Makes me wonder if we should be testing samples before installation ?

A full and proper test requires relatively elaborate lab facilities, but perhaps a crude test involving say a vehicle battery and a 100 amp fuse.

This wont reveal all faults, but would at least weed out the most blatant "no trip" types.

An MCB tested thus might of course have been damaged, so perhaps test the odd sample and only install untested examples from the same batch. Rather expensive though.
youtube. fake MCB dismantled
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    I have always wondered why MCBs are not tested, at least on initial verification. Perhaps it is too difficult? But we wouldn't install an RCB without verifying its performance.


    However, the chance of getting one of those from Eddie's, Rexel, CEF, Screwfix, etc. must be less than winning Euromillions.
  • 0
    To safely trip an MCB on a car battery without burning the electrodes requires you to keep the PSSC well  below 6KA., and the voltage low enough not to draw an arc.

    I suggest the average set of economy jump leads will do quite a lot of that current limiting without too much difficulty, and the pssc of most car batteries is in the single figures of KA anyway, at least in cars, perhaps not in some monster truck.

    The one in Mrs Mapj's car got changed when the internal resistance rose above about 8milliohms, as at that point the auto start-stop stops working, the new one was about half of that. - so a PSSC of perhaps 3 to 4 kA.

    Mike

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    I doubt that a car battery could deliver  6KA. The maximum cranking amps are often in the region of 200 amps to 300 amps, at which current the voltage drops by at least 10%, that in turn suggests a maximum short circuit current of very roughly 2KA to 3KA.


    12 volts DC can not maintain an arc, the minimum is about 18 volts.


    So testing with a car battery is rather basic, but would weed out the worst examples
  • 0
    broadgage:

    I doubt that a car battery could deliver  6KA. The maximum cranking amps are often in the region of 200 amps to 300 amps, at which current the voltage drops by at least 10%, that in turn suggests a maximum short circuit current of very roughly 2KA to 3KA.


    12 volts DC can not maintain an arc, the minimum is about 18 volts.


    So testing with a car battery is rather basic, but would weed out the worst examples


    Wouldn't it be easier to set up a 240 Volt test rig with too many electric fires plugged in, to test a miniature circuit breaker. That might be easy for a B6 or B16 M.C.B. For a B32 or B40 a dedicated rig with many well ventilated resistance elements would be good. An Ammeter could be installed in circuit, or a clamp meter to read the actual current flowing. Then normal A.C. can be applied. The rig could have temporary shrouded spring loaded hinged contacts for the M.C.B. terminals so that multiple testing could be done. 


    Z.


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    broadgage:

    So testing with a car battery is rather basic, but would weed out the worst examples


    Not all circuit breakers are suitable for dc, so testing with a car battery could end up rejecting perfectly good breakers.


  • 0
    The mains overload test is very wasteful - you only need the amps not the volts to perate the trip part. I agree for testing a B6 it may well be fine to use 30A of load, but the idea does not scale well to get enough amps for the larger MCB - consider the need to instant trip a C type 63A unit - if it does not trip the rest of the morning may be lost to getting the company fuse changed.

    Testing the thermal part of a breaker may be OK, at least in the smaller sizes, but  for the prompt trip tests I suggest that something more like a welding transformer would be in order.

    Mike.

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    Does anyone know what sort of supply equipment John Ward uses when he does his "lets run 60A through a Wago"-style videos?
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    Yes, he has shown us in a vid I cannot find now, it is an arc welding transformer, though he has a variac as well.... The door of the garden shed and piece of singed OSB are also essential tools to the seasoned experimenter.

    Mike.
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     consider the need to instant trip a C type 63A unit - if it does not trip the rest of the morning may be lost to getting the company fuse changed.


     


    A rare beast in the domestic world I feel. And even in shops and offices.


    Z.


  • 0
    Zoomup:
     consider the need to instant trip a C type 63A unit - if it does not trip the rest of the morning may be lost to getting the company fuse changed.


     


    A rare beast in the domestic world I feel. And even in shops and offices.


    Z.




    Possibly a C63 is an extreme example (but not unknown for say submains to remote CUs) - but even a relatively common B50 would need 250A to test for instantaneous operation - which won't to the DNO's fuse much good if it persists for long.


       - Andy.


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