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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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    Funny reading this here as I had the same problem in the week. Some background. Been in the trade for a few years now. Gone from selling the parts to fixing small appliances to big appliances to small repair work to bigger installations to massive 3phase installations to being a maintenance electrician for a bit more than 10 years. Having all that experience behind me when the time came to redo my kitchen I went a bit nuts and installed 8 sockets on about 3 different breakers feeding them. No way nothing is tripping no matter what the wife gets up to in there. I need to mow the lawn so I plug the lead into the socket closest to the back door. Go to start lawnmower (2.2kw). Starts and dies. Mmm funny. Go inside reset breaker. Try again same thing. Check plugs in kitchen nothing plugged in or switched on. Try a different plug further away no problem. Finished mowing the lawn and the problem still bothers me. Go to check again and see that the breaker that is tripping is 1 of 2 old hy mag samite breakers with the big toggle. I think its fair to say its time to replace him and his friend as the are probably 20 or more years old ? and retire them to the in case of emergency box of second hand breakers on the bottom shelf of my store.

  4. #4
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    I have been having some strange tripping issue lately ... lights have been flickering ever so slightly ... but not all the time.

    Switch on the aircon ... the breaker trips ... switch on the compressor ... the the breaker trips ... turn off the oven and use the aircon ... it works ... eeeeish ... I thought i might need a sparky.

    checked all the neutrals ... found the main neutral feeding the house a bit loose ... tightned it ... no more tripping.
    Comments are based on opinion...not always facts....that's why people use an alias.

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