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Thread: COC issued with faulty circuit breakers.

  1. #1
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    COC issued with faulty circuit breakers.

    Hi all

    Thought this may be of interest to my brothers.

    Recently, I issued a COC for a domestic installation with 6 plug circuits, each protected by a 20A CBI circuit breaker.
    All inspections and testing were carried out by the book and no faults were found on any of the plug circuits.

    I make use of a resistive load on all socket outlets that draws 15 Amps. All passed with voltages within limits whilst under load.

    COC issued after minor repairs attended to and I was very confident that the installation was compliant.

    A week after the new owner moved in, I get a call. Plug circuit breakers are tripping.
    Drop everything and go and have a look.

    3 of the plugs circuit breakers could not handle the instantaneous starting current drawn by an angle grinder. These 3 circuit breakers could handle the 15 Amp resistive load, but couldn't handle the starting current of an angle grinder.

    Replaced the circuit breakers and problem solved.

    Fortunately, the new owner understood that this problem could not be detected even by doing the testing by the book.

    From now on, an angle grinder is gonna form part of my testing kit.

    Peace out ... Derek

    Peace out

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    Quote Originally Posted by Derlyn View Post
    Hi all

    Thought this may be of interest to my brothers.

    Recently, I issued a COC for a domestic installation with 6 plug circuits, each protected by a 20A CBI circuit breaker.
    All inspections and testing were carried out by the book and no faults were found on any of the plug circuits.

    I make use of a resistive load on all socket outlets that draws 15 Amps. All passed with voltages within limits whilst under load.

    COC issued after minor repairs attended to and I was very confident that the installation was compliant.

    A week after the new owner moved in, I get a call. Plug circuit breakers are tripping.
    Drop everything and go and have a look.

    3 of the plugs circuit breakers could not handle the instantaneous starting current drawn by an angle grinder. These 3 circuit breakers could handle the 15 Amp resistive load, but couldn't handle the starting current of an angle grinder.

    Replaced the circuit breakers and problem solved.

    Fortunately, the new owner understood that this problem could not be detected even by doing the testing by the book.

    From now on, an angle grinder is gonna form part of my testing kit.

    Peace out ... Derek

    Peace out
    It is not uncommon for inductive loads ... like "big angle grinders ...pumps ...aircon etc. to trip standard 20 amp domestic C curve circuit breakers.

    You will find many aircon units with 25 amp C curve breakers ... you should install a 20 D curve breaker ... however in saying that the new inverter type aircon cause the D curve breaker to buzz for what reason I have no idea.

    I am sure there posts on this platform which go into detail about the selection of circuit breakers.

    I would have charged the new customer a call out fee and the cost of a replacement circuit breaker ... there is complaining about illegal installations and then these customers ... I had one the other day who was complaining because the main ... was a "little" tight when trying to switch off ... I sent him a quote to replace the main switch ... he stopped the transfer but the previous owner chose to pay for the main switch to be replaced ... if it had gone the whole legal route ... AIA DOL etc. ... at the end of the day the installation was 50 years old and "reasonably safe"... there was nothing illegal about it.
    Comments are based on opinion...not always facts....that's why people use an alias.

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