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Larry Larry is offline
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First recorded activity by BoatBanter: Jul 2006
Posts: 5,275
Default How many DC amps is too much

"Roger Long" wrote in
:

"Jere Lull" wrote

When we're on Xan, we are connected only as we wish.


That's the biggest reason I would like to install refrigeration, to be
a bit less connected to the shore for cold stuff.

You're right about the cost though and it isn't just the installation
and fuel. A good diesel mechanic up here told me the first question
he asks when a sailboat owner says they are having trouble with their
diesel is, "Do you have refrigeration?" Unless they have a separate
generator, he knows right where to start looking for the problem.

--
Roger Long





While we're talking fridges and power requirements, I'd like to describe
a 2.2 cu ft dorm fridge I bought a few years ago for a pittance at a
thrift shop, probably $10. It's seen hard dorm use. I replaced the
door gasket and repaired the plastic inside the door. It's a Norcold,
but I can't find any model plate, sorry.

What's neat about this little fridge is in the back....it's compressor.

Wrapped around the back of the fridge is a rather large, for its size,
condensor that is stood off the fridge so it doesn't heat the
case....you know...like the NEW fridges do...which is stupid. Between
this wrap-around condensor and the rear wall of the fridge is a steel
cylinder about 3" in diameter and 9" long sitting vertically. ONE wire
comes out of it and the steel case is the other conductor. This doesn't
matter because it runs on 40 VAC 50-60 Hz. The compressor gets this
voltage from a little transformer that is specific to the country
they're shipping the unit to. In our case, the transformer is 120VAC to
40VAC. In Europe they use the same compressor, just a 240VAC
transformer.....very logical.

This odd little compressor is not a motor at all! It's a solenoid
driving a single cylinder little pump. The AC makes the plunger in it
vibrate back and forth at 60 Hz, which is also the piston in the
pump...only ONE moving part! I suppose it has reed valves.

We'd not be allowed to build these, today...It uses R12 refridgerant
because R12 is the most efficient and lowest pressure, the reason they
used it for decades in cars before the Algores drove us crazy with the
lie of Global Warming caused by AMERICAN FREON, which was BS to raise
the price of freon from 60c/pound to $10/pound...another story
altogether. The Antarctic ozone hole is LARGER, now that we have
stopped the production of Freon 12, obviously not reported to an irate
nation, because it has nothing to do with it.

Now, using R12 low pressure refridgerant and this little plunger pump is
MOST impressive for use in a vehicle or boat! IT ONLY DRAWS 40 WATTS
WHEN IT'S RUNNING! To use it in the car on a trip, I plug it into a
tiny inverter from Radio Shack rated at 75 watts, built right into the
cigarette lighter plug. I'd bet the whole thing draws 42 watts ONLY
WHEN IT'S RUNNING, which, of course, depends on how much beer it's
cooling and how many times the door opens. there's room in its
"freezer", inside the evaporator sheet metal with a little door, for 2
trays of ice cubes and it will make ice in about 90 minutes. It will
also keep ice cream sandwiches frozen hard packed in there, too.

My calc shows this to be about 3A at 13.8VDC. If it ran wide open,
which it doesn't or we'd have frozen beer in a day, that's only 72AH in
24 hours. It's probably about 60% of that or 43AH per day.....which is
MUCH BETTER than a portable absorption fridge for the car which uses 4A
continuously and doesn't cool worth a damn.....

These fridges, if you are perusing thrift shops, are easy to spot. The
evaporator and beer-can-shaped cylindrical compressors stick out the
back because the compressor must be vertical, not horizontal, in
operation. This shape distinguishes it from the power hog motor
compressors that are squat and fat in most fridges.

It really does keep the beer COLD....for just a little power.....