WRT  fridge/reefer  current draw.

In view of all the  comments  regarding current draw, it seems to me that
one of the best cruising setups might be a small engine driving a  huge DC
alternator ( approx 300 Amps ) which also drives  cold plate refrigeration
unit and possibly a water maker.

The 300 Amp alternator would have a smart  3 or 4 stage regulator to
properly charge up a battery bank.  The  cold plate  compressor would  draw
down the temp in a top loading chest freezer / fridge built with extra
thick  insulation  and the water maker would add to the  drinking  water
supply.  This latter would of course be an option.

The  300 A alternator  needs about 6 horsepower, the  water maker about 3
and the cold plate compressor about 3 -4 horsepower.
Balmar offers  a 15 HP Yanmar diesel which drives such an alternator and
belt drives a water maker pump.  They are  making up a custom bracket to
belt drive another  device off the other end of the  crank shaft.

A daily  two  or three hour  run would go a long ways towards recharging
the  freezer,  batteries and even the water tank.

24 hour use cycle.

The  littel diesel would be loaded  close to its  80% rating and would thus
be  at its maximum  efficiency.  Its small size makes it easy to  suppress
noise and vibration while tucking it away in a corner of the engine room.
The  limited amount of  exhaust is also easy to quieten down to a  faint
level.

For those who want  the convenience of an upright apartment fridge, add an
inverter to drive the 120V AC  house appliance.
A two hour run will add a maximum  of 600 A-H  to the house battery bank.
Assuming this amount is consumed in a 24 hour period;  it makes available
an average  power consumption of 25 amp hours.
The high number for a fridge draw I saw in previous postings is  about  13
amps so that leaves  a little bit left over for  lights and other  things,
even if the cold plate freezer option is not used.

I do  not think an alternator belt driven off a main engine is the solution
for boats that  spend a lot of time anchored in one location.
Running a main propulsion engine to draw off 6 HP  to an alternator is
simply not efficent.
It would however be  the  right choice for a boat  which  runs for long
periods and is docked  with access to shore power the rest of the time.

For those who want to check my numbers:

300 Amps @ 13.5 volts =  4050 watts.

756 watts = 1 hp    so  300 Amps = 5.357 HP    Round up to  6 HP to
account for  losses

Assuming a .34 Lb/hp/hour consumption rate we get  6 X .34 =  2.04 lb fuel
burn per hour. which is about one US quart of fuel/ hour

( Paul Kruse, can you confirm or improve on this number? )

So we get a daily fuel  burn of  2 quart to handle refrigeration and
recharging the house bank.

In order to  absorb the full 300 Amp per hour charge we should use good
deep cycle house batteries.  Regular flooded lead acid cells  can only
handle  a charge rate of 20% of  A-H capacity  ( C/5  to use the correct
formula )  which  would require a bank of at least  1500 AH capacity.
Remember that you can only  use 50% of a battery bank's full capacity.
This means that  in order to be able to use the full 600 A-H you would need
a  1200 A-H capacity  bank.

However if you have a  lower energy consumption  overall, then you can
reduce the battery bank size accordingly  and not have to use such a large
alternator.

Does anyone have  or know of a table of average  power consumption for
various appliances.  This would take into account  duty cycle and startup
surge.?  I'm looking for something which  list  products by brands or at
least size capacity.
I am  trying to come up with a formula for optimum  cycling time; taking
into consideration  average draw and peak start-up surge.

Cheers

Arild

JB0847@aol.com wrote:

Norcold makes a small top-loading refr/freezer that was considered in one of the
review newsletters to be the top of the line. It runs on AC or DC.

I have one that's many years old, running on AC, and can set it to cool or
freeze. It's mounted on the bridge deck, which makes cold drinks and pre-made
lunch salads handy at noon while steering, and it's not too far to come up and
get something for the galley when it's used for a freezer. I have a thermometer
inside, and even in the occasional sun, it cools really well. It seems that
Norcold insulated this one adequately, or maybe it just runs a lot -- I don't
know. Quiet, hermetically sealed compressor, long lifetime.

We made a hinged formica top edged with teak so it serves as a small table as
well. I'm planning on getting a second one for the other side of the deck so we
can use one to cool and the other to freeze.

--
Regards --- Don Dement