Strange breaker story

Discussion in 'Electrical Forum discussion & Blog' started by TubeGuru, Mar 25, 2013.

  1. TubeGuru

    TubeGuru Unretired defense industry engineer

    Aug 27, 2010
    Redmond, WA
    My folks live in a gated community in Tucson. My sister is minding the house, which is about 30 years old, and had a strange story to tell.

    "Microwave was running. Electricity went off in living room (lights and TV), dining room and hall lights. Kitchen lights still on, fridge on, d/w on, but microwave display was black and no light inside when opened. Microwave seems to be wired into lighting circuits. So when microwave tripped, all others on that circuit, 3 rooms of lights, went with it. Stove display on (not connected to microwave). Breaker box on front of house next to meter. The light blue breaker was tripped, mushy, would not move back with a snap, kinda mushed back to center."

    "This morning went out and turned off/on the black Service Main breaker. Then turned off/on the red Kitchen breaker, then reset light blue Microwave breaker. Actually, all the light blue ones are were affected (3 rooms of lights) but the microwave was the only one in off position. The 4 light blue ones are collectively labeled Lighting, but one of them is also labeled Microwave. So it was two of the light blue ones that were affected, one controlling Microwave and the other controlling living room, dining room and hall lights. I think once I reset Main, all was reset."

    I don't understand how resetting the main breaker could improve the situation of any other breaker downstream. Or how the Microwave breaker, when off, could affect the 3 other Lighting breakers (since those lights were also off). And what about the inability of the Microwave breaker to be reset? Mushy one day and resettable the next?

  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    IF the microwave is in the kitchen, those branch circuits should stay in the kitchen. Sounds like whomever wired things went the cheap way and ganged lots of things together. As to the CB 'feel'...I suppose it could be a function of how hot the thing got. If there isn't a wiring fault, and it was a long-term overload, it could have gotten hot before it tripped. Most CB trip fast if there's a short, but load it up to max or even above, it can take a bit of time before it trips...this can make it at least warm, if not hot. Overnight, if it had tripped earlier, it would have had a chance to cool down. There could be an actual wiring error, but that would take some careful examination, and can't be done from afar. CB do wear out, but often have a very long service life.
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  4. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona
    It is possible, although it would be a "reach", for half of the main breaker to trip, which would shut down everything on that half of the box. IF that had happened, it would indicate a bad main breaker, and no 220/240 volt item, such as air conditioner or kitchen range, would operate.
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