Thursday, October 31, 2013

The Lowly Water Pump

All refrigerators pull heat from inside the refrigerator and expel it--somewhere.  Most refrigerators have a radiator, and sometimes a fan as well, used to disperse the heat to the surrounding air.  For a refrigerator that runs nearly all the time, like an ordinary land refrigerator, the heat generated at any particular time is minimal, and the air-cooled method works just fine.

Our refrigerator, however, is designed to run for only a couple hours a day.  During that time, it pulls a massive amount of heat out of the box in order to freeze a steel block that, like a big block of ice, keeps the refrigerator cold for several hours.

Cooling
Because the refrigerator generates substantial amount of heat in a short period of time, it needs to be water-cooled to more efficiently dissipate the heat.  The system is simple enough--a little pump pulls water from the ocean, runs it through the refrigeration system, and spits it back out into the ocean.  The problem, though, is that if the water pump does not work, neither does the refrigerator.

This is what happened to us this weekend, when our refrigerator stopped working.  The same problem happened almost a year ago, but we fortunately had a spare water pump at that time.  This time, no working spare.  The pumps are rated to last for 3000 hours, which at 2 hours a day, is over 4 years.  The pump we installed a year ago did not, of course, last 4 years--it lasted one year.  The spare came with Sea Gem and may have already been previously used for a different purpose, leaving it with only a quarter of its life span.  Also, when we ran out of freon earlier this year (this has not been a good year for our refrigerator), the pump ran almost constantly for a week or two while the refrigerator struggled to stay cold.  In any case, the pump died, leaving us with no working refrigerator.

And so I ordered a new pump, an updated version of the old one.  This pump uses a different type of motor (brushless) and is rated to run for 50,000 hours--at 2 hours per day, that is over 68 years.  Do I expect it to run for 68 years?  Of course not.  Part of the magic of boat ownership is that everything breaks before it is supposed to and at the worst possible time.  But I sure expect it to last a good deal longer than one year.  Stay tuned for an update sometime before 2083

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