"Jeff" wrote in message
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* Wilbur Hubbard wrote, On 8/10/2007 6:46 PM:
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I must inform you if your fridge draws 30 amps at 13VDC then there's
something seriously wrong with it. Mine only draws 5 amps. Hell, you
could run an air conditioner on 30 amps.

It would seem that we can add yet another topic to the long list of
nautical issues where you seem completely ignorant.

And it would seem you're drawing conclusions based on scanty information
yet again.


First of all, 30 Amps DC won't get you a lot of A/C, though I must
admit I haven't looked into to smaller units. (The smallest one West
has would be about 50 Amps DC for 5000 BTU.)

However, a 30 Amp draw is quite common for my type of fridge. Its a
1/2 HP motor driving a compressor that feeds several holding plates in
a 9 cu ft fridge and 5 cu ft deep freeze. The actual load varies from
20 to 35 Amps. Here in Maine I've been monitoring it carefully, and
it has taken about 40 Amp-hours per day for the last two weeks. The
fridge stays at 42-46 degrees, the freezer at 15-20, both measured at
the top shelf.

What you're doing is pretty wasteful. Sounds like you have a separate
freezer and refigerator. That's dumb. All you need is a freezer that
connects to your fridge box with a well-insulated duct. Keep your
freezer full of meats and other dense stuff and run it all the time.
Allow some of the excess cold air to migrate into your fridge box by
controlling the size of the duct. The duct should run from the top of
your freezer box to the bottom of your fridge box. If you do this, you
could run the entire system on one modern, efficient Danfoss compressor.
Holding plates are a stupid system because they are bulky and take up
too much room inside the ice box. Better to have a flat or box-shaped
evaporator and use meats and other dense frozen foods as the holding
plate. What I do is completely fill the freezer part with canned beer.
The Ice beer works best because of the high alcohol content it doesn't
freeze and bust open. But, the thermostat cant' be set to the cold
position. About 1/4 the way to all the way cold works best. My freezer
contains 15 twelve ounce beers. I relpace them one at a time as I drink
them. I maybe drink six on a hot day. I cycle new beers from the fridge
section to the freezer section and add new ones to the fridge section as
I drink them. An admirable holding plate.

My box is very-well insulated and because of it my compressor usually
runs 20 minutes on 40 off in the summer and about 15 minutes on and
close to an hour off in the cooler months of winter. Let's call that
one-third of 24 hours for 8 hours total or 40 amp hours. The box
measures about 1.5 feet by 2 feet by 1.5 feet. For about 4.5 feet cubed.
It and everything else is run by two Evergreen 100 watt photovoltaic
arrays connected to a Sunsie charge controller. The fridge runs more in
the summer months but the days are longer too so the batteries stay
well-charged the year around.


Your system probably has a Danfoss hermetic system and runs about half
of the time, depending on the load, so you actually use about 60
Amp-hours a day. And your fridge/freezer is probably half the size
of mine, and not as cold.

Frankly, I've been thinking that is I did my system today I might use
two modern Danfoss systems, so I could shut down the freezer when not
needed. However, the last time I charged it up I seem to have got it
right and the efficiency is quite high. I curious to see how it works
when we get back into warmer waters in a week.

Like I said above I think you could get away with using one. But your
ice box/fridge would have to be well insulated and close to each other
for it to work well. Most ice boxes are poorly insulated. I know a
fellow who built a 60 catamaran named Shadowfax. Cold molded cedar strip
planking method diagonal layers. Of course he built his own ice box
which was rather largish. He poured one foot of foam all the way around
even on top. He could put fifty pounds of ice blocks in the damned thing
and it would last two weeks. I was amazed. If you have the room, one
foot of insulation all around is the way to go.

Wilbur Hubbard