Behind The Magic: Your Garbage Disposal

In this wondrous world in which we live and breathe, it's easy to take things for granted. How many of us have heated up a delicious DiGiorno frozen pizza for dinner, eaten half of it, and then stuffed the remaining half into the "in-sink-erator." Did that pizza rot in the sink? Of course not! With the flick of a switch, viola! The pizza is gone. Magic? In a sense; it's the magic of modern living.

But have you ever asked yourself, "How exactly does a garbage disposal actually work?"

Luckily for our readers, Britt recently attended a conference for fact enthusiasts and sat in on the most interesting lecture on how a garbage disposal actually works. Here is what he learned:

The Basics

The way a garbage disposal functions is really easy to grasp. It is a basic machine with a few “easy to grasp” principles. The first thing to know is that a g.d. is basically a split circuit machine that runs off of simple 120 volt electricity. The circuit gets split (to 60 volts per cycle) when the wire, which naturally is not user-accessible as g.d.s are hard wired, comes up through the sink and splits to meet each end of the bi-orbital base where the wire tips are spot welded with a mig or tig. This is so the same pattern of mulching is not repeated, much like a chewing motion.

Where Does the Food Go?

Above the base made of steel is a cantilevered blade that has been impregnated with a magnetic field. The blade is usually alloy as it needs to be lighter than the base and it is attached to a beveled set of ball bearings that are free to move as far as the rotation arm will allow due to space constraints (see diagram). This is as long as the electric waveform stays positive which can be explained with this simple concept: waveform for power is always positive, never negative in a resistive circuit like this one. This means that power is always being dissipated by the resistive load and never returned to the source as it is with reactive loads. If the source were a mechanical generator, it would take 240 watts worth of mechanical energy (about 1/3 horsepower) to turn the shaft.

How Does It Get Power?

Being hard-wired, the garbage disposal is independent of the wall outlet ground system. This means that even if your wall outlets are two-pronged (polarized), you can still run a separate ground circuit for the disposal. Also note that the waveform for power is not at the same frequency as the voltage or current. Rather, its frequency is double that of either the voltage or current waveforms. This different frequency prohibits our expression of power in an AC circuit using the same complex (rectangular or polar) notation as used for voltage, current, and impedance, because this form of mathematical symbolism implies unchanging phase relationships in the garbage disposal. But phase relationships ALWAYS change! When frequencies are not the same, phase relationships constantly change. As strange as it may seem, the best way to proceed with AC power calculations is to use scalar notation, and to handle any relevant phase relationships with trigonometry. Counter-intuitive? Sure. But if you really stop to think about it, it should all become quite clear.

In Conclusion

Garbage disposals are used all over the world and have been a great help to mankind.