rob-jax you helped before with my electrics got another quest...

[dazicki]

hiya ,as ive explained before on site my elec went off and in the fuse box there are 2 switches.we only have a fridge and a plug socket so one of them was still ok the other had flicked off and wouldnt come back on anyway went down the other night thought wed unscrew the socket see if it was a loose wire just about to do it when i thought ill just try the switch and it flicked up and stayed up????????????????????why?????

is it that after a major trip like that it will take a few hours to come back on like a time lapse to protect the system???

can you help

 

[rob_jax]

Hi,

MCB current limiting trips are affected by internally generated heat - usually from a loose connection.

If the MCB has tripped - and it's hot inside either because of a fault in the MCB or loose wiring - then it may well trip straight away. When it's cooled down - it may work properly until it trips again.

So - you may want to check that all the wiring connections are properly tightened and in good condition - but if the MCB has an internal fault, it will get hot again, and trip.

If you can try it at home, see if it trips after an hour or so - and maybe replace the MCB anyway.

Robert

 

[gary]

Single pole MCB's work in two ways, their main function is if two much current is being drawn through it will heat up and trip, it will then not reset until it cools down sufficiently. In this respect then a bad connection will cause the MCB to 'self heat' while under normal load and the two combined can cause a 'trip'. However in normal cases the time is measured in seconds while abnormal overheating will take longer to cool down.

However with modern MCB's, they trip 'half way' you then need to push it all the way down before pushing back up to reset it, perhaps that's what your problem was?

As I said there is an another function which I'm not sure about and with twin pole MCB's yet an another function which would prevent a reset while a faulty appliance is connected.