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Kitchen Lights Tripping Lights Fuse Intermittently

Postby panagath » Tue Mar 03, 2020 8:53 pm

I have the problem that the kitchen lights intermittently trip the fuse of the ground floor lights. I have narrowed it down to the kitchen lights. Some times it will trip right when I press the switch...some times after a long time of the lights running. Maybe even a couple of days in between.

The lights were recessed lights in the void using 6 12V transformers. I removed ALL the transformers and connected one typical bulb. I was hopping this would stop it and it would be the transformers but unfortunately it tripped again.

Any suggestions? Could it be the wall switch? The visible part of the cables looks in good condition. There is nothing else connected to that switch.
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Simply Build It

Postby ericmark » Wed Mar 04, 2020 6:15 pm

A fuse does not trip, it ruptures, and then needs replacing, so question one has to be what it tripping?

We have a number of things it may be, and the answer does depend what.

The MCB is a duel unit, it has a magnetic and thermal part, they will normally be marked B6 or C6 the B means the magnetic part will work between 3 and 5 times the thermal part and the thermal part is 6 amp, with tungsten bulbs when they blow the magnetic part of the trip may work due to the very high current caused inside the bulb when the gases inside it ionise (bright flash as bulb blows) but in the main it is the thermal part that trips, and it takes some time to warm up, with the MR16 ceiling lights 50W each total wattage could exceed 1380 watt which is 6 amp, so it could be simple over load.

The RCD has a test button, and is designed to open if there is an imbalance, the imbalance is normally due to some power going to earth, often one RCD will feed many MCB's.

The RCBO is a RCD and MCB combined, so three devices in one.

Some wall switches need current flowing through the switch to work, I have some of these, a push button which can also be worked by remote control and phone, any lost in power, will cause it to switch off, loose wire, blown bulb etc.

Need to know what you have to try and work out what is going on.
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Postby Mr White » Wed Mar 04, 2020 7:49 pm

Pictures please, what exactly trips?
Its just that fuses go bang, MCBs trip as do RCD's and often it is the RCD, you may even have RCBO's
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