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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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    Alasdair Anderson:
    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.




    I would expect any common type of MCB to work fine on 12 volts DC.

    The thermal or magnetic trip mechanism wont know the difference. And the actual opening of the contacts is done by releasing a spring.

    Higher DC voltages are more problematic since DC tends to arc much more than AC and this may damage or destroy the MCB.


    I would use or test standard MCBs on up to about 24 volts DC, but not on any higher DC voltage unless the supplier confirmed IN WRITING that the MCBs were suitable for the proposed use.


    12 volts DC can not form an arc. 24 volts DC CAN form an arc, but no worse than 240 volts AC. A good rule of thumb is that switches, circuit breaker contacts, relay contacts and the like that are marked "AC only" can in fact be used on DC but only at about 10% of the voltage.


    I would use standard "240 volt AC only" light switches on a 24 volt DC circuit, but not on any higher DC voltage.


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  • 0
    Alasdair Anderson:
    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.




    I would expect any common type of MCB to work fine on 12 volts DC.

    The thermal or magnetic trip mechanism wont know the difference. And the actual opening of the contacts is done by releasing a spring.

    Higher DC voltages are more problematic since DC tends to arc much more than AC and this may damage or destroy the MCB.


    I would use or test standard MCBs on up to about 24 volts DC, but not on any higher DC voltage unless the supplier confirmed IN WRITING that the MCBs were suitable for the proposed use.


    12 volts DC can not form an arc. 24 volts DC CAN form an arc, but no worse than 240 volts AC. A good rule of thumb is that switches, circuit breaker contacts, relay contacts and the like that are marked "AC only" can in fact be used on DC but only at about 10% of the voltage.


    I would use standard "240 volt AC only" light switches on a 24 volt DC circuit, but not on any higher DC voltage.


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