I am in Australia, with 220-volt single phase power. My electricity distribution control panel has 6 switches, of which two, call them A and B, control wall power points. My juicer is plugged into one of these power points, which is controlled by the A switch. Using the juicer often causes the B switch to open while the A switch remains closed.

I am sure that the juicer is not in the B circuit because it continues working when the switch opens. I know what the A circuit controls by experiment with other equipment. My question is not why a switch opens when overloaded, but why does the wrong switch open?

Can anyone explain what is going on?

  • Three questions. 1) In terms of which breaker controls which outlets, are you going by descriptions written on a label in the breaker box, or did you actually switch off each breaker to confirm which one controls the outlet? Within a room, outlets are often split between breakers so everything in the room doesn't go out if something on one outlet trips the breaker. 2) is breaker B a GFCI breaker? 3) Kitchen outlets should be on GFCI circuits. These are usually built into one or two of the outlets. Are you sure that what is opening is actually breaker B?
    – fixer1234
    Jun 12, 2017 at 8:02
  • Are any of these curcuit breakers GFCI, or as you might call them RCD or RCBO? Do they have a "test" button on them? Jun 12, 2017 at 13:18
  • 1
    I've seen this happen before with an old circut breaker panel that needed replacement. Specifically what happened in that case was breaker A had a bad connection to the buss bar, the result of the bad connection was heat, which would cause the adjacent breaker to trip. (In this case the load on A, coupled with the bad connection, was actually causing the aluminum buss to get red hot.). If the circuit breaker panel is old it may have internal problems.
    – Tyson
    Jun 12, 2017 at 13:30

1 Answer 1


Well I'm from America living in North Carolina but I can take a stab at it because I have a similar problem with my home. It will overpower by using too many amps. So you need to find out how many amps are on your A and B switches. I went through my house and marked everything with a removable sticker for each switch and each outlet. Then by process of elimination I found out which on/off switches and which outlets were controlled by either the A or B fuses in the box. Then you need to know how many amps your A/ B fuse can handle. If you have a 15 amp fuse then you cannot use more than those 15 amps at any given time. I hope this helps.

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