Well everyone said you could not use a 120v fridge on a sailboat. I had read that alot. But being blonde and having an engineering background, I decided to buy the cheap
120V fridge and try it out. After all a BTU is a BTU. Plus if it did not work out I could get the better 12V system later.
Yes at first blush the 120V fridge uses way too much amperage. But I found by sitting and actually timing the on/off cycle one hot summer day in the delta
that my little 120V fridge only ran about 2-1/2 minutes then had 10-12 ish minutes off. I checked several cycles over a few days of 90+ degree days.
I was surprised to find that my energy hog 120V refrig. actually only used about 2.5 amps an hour (including inverter loss) during the heat of the day.
The other issue some raised was oil
starvation. But the basic compressor
design is the same between the 12V and 120V systems. Nothing special with the 12V. Matter of fact the 12V compressor
has an AC motor
with a DC to AC drive (the mysterious black box).
After 5 years of sailing (admittedly not that much sailing for the first 2-3 years). But I've logged over a 1000 miles in 2011 and its going to be over that for 2012. OK Not long distance cruising yet.. (That's next year
) But with the boat sailing in the brisk San Francisco
winds, its been doing fine. Even healed over 25 degrees or more.
To me looking at the different refrigeration
systems on the market, its seems there is not really any real world difference between power consumption on 12V compressors and 120V comressors on a per hour usage. Its true that the 120V fridge will use more amps when it runs. But it runs only 1/6th the time, compared to 1/3 to 1/2 or more for a marine
Its sort of like which heating
element uses more energy to heat 40 gallons of water
, a 4KW or a 40KW. The answer is they both use exactly the same amount of power, just that one heats the water much faster.
The main difference in energy savings comes in the amount of insulation "R" factor the cold box has. That's about the only real savings you get. More insulation means less run time on the compressor. Besides that the basic 12V and 120V hermetic compressors will use the same energy to cool a given size box.
Oh sure water cooling
will give a little more bang for the buck. But only where the water temperature is much cooler then the air temp. In the Sea of Cortez
in the summer a water cooled compressor will be working pretty hard too.
The joy of the $140 fridge is when it goes out, you toss it away and get another one for less then a service
call from a marine AC tech. So far mines been working fine for 5 years running and me being a full time liveaboard