Had a funny one happen yesterday. The kitchen garbage disposal was
running, but sounded like it was full of scrap iron because one of the
rivets holding a flail onto the macerating disk had loosened and let
that flail chatter against the housing, making a horrid scraping.sound.
I picked up a same brand/same size replacement disposal at HD and got it
swapped out in a record breaking (for me) 36 minutes, winning my bet
with SWMBO who scoffed when I told her she's be able to use the kitchen
sink in 45 minutes or so. (She's usually the winner, my repair project
time estimates are generally low by at least 200%.)
When I turned on the water and flipped the wall switch, the disposal
motor didn't start. After saying, "WTF?" I tried the electric can opener
which I knew was on the same circuit as the disposal. When it didn't run
either I went down to the panel and found the GFI breaker for that
circuit was tripped. I reset it and when I came back to the kitchen the
can opener worked fine. I flipped the switch for the disposal and the
GFI breaker popped again.
I checked my wiring at the disposal and to my embarrassment I found that
the stranded neutral motor lead wire hadn't "caught" in the wire nut,
and was just hidden inside it, but not connected to the supply neutral.
And, for sure none of the supply or neutral leads were contacting
gounded metal. Things were sort of tight and cramped inside the wiring
compartment of the disposal, but that's really no excuse for my sloppy
job, is it?
Anyway connecting that motor wire to the neutral side of the supply put
I'm assuming that the motor's winding to ground capacitance caused
current to flow through the supply side of the GFI which wasn't
returning on the neutral side, and that unbalance tripped the GFI.
If it wasn't such a PIA to crawl under the sink again, I'd disconnect
that neutral lead and test my theory.
Jeff Wisnia (W1BSV + Brass Rat '57 EE)
"If you can smile when things are going wrong, you've thought of someone
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