??? about keeping refrigerators cold
 

The way that this problem is normally solved is by adding a standard
icebox 12 volt conversion unit in the existing refrigerator. There are
several manufacturers that have thin plate evaporator coils that will
fit the rear wall of existing refrigerators. In the new Boat Works
magazine there is a article of a similar conversion to a 110 volt
refrigerator.

Storing energy in cold packs will not cool the box to refrigerator
temperatures.

From the author of four books on boat refrigeration
For a slide show on boat refrigeration go to;
http://www.kollmann-marine.com





Terry Spragg wrote in message t.cable.rogers.com...
wrote:
I have a large refrigerator and don't want to get rid of it since I'm
on the boat a lot, and the majority of the time at the dock. But do
like to go out for a couple of days each week, and the biggest
issue is the frig getting too warm unless the generator runs more
than I like it to. Do they make good cold packs of some kind that
can be frozen and re-frozen, and would help keep it colder without
so much use of the generator?

Like big blocks of home made ice? Phase change chemical salt "cold
packs" could offer some similar assistance.

Keep the door closed. Only more insulation can really help you.
Insulate especially between the compressor, radiator and the cold
chest, possibly increasing the insulated space between them by
extending the refrigerant lines.

Have you considered the technology of CO2 (dry) ice, or liquid
nitrogen? You could pump up a few gallons of Ln2 for use while the
engine is not used, etc. Well insulated dewars can keep Ln2 in
storage for some time, but the engine must still produce the energy
to produce this cold storage heat sink.

Some will say that using much dry ice may poison occupants during
sleep. Ln2 could displace O2, but not so likely as CO2, depending on
equipment failures.

Ln2 is relatively lightweight, and can be stored in floatation
space, ie. forepeak, etc. Piped into the freezer under the control
of a cryogenic thermostat, it could keep the contents cool, and
could possibly be "recharged" by the addition of more liquid
nitrogen, poured from a transport dewar to operational dewar aboard
the boat. It is a form of phase change heat energy storage system,
where it's evaporation provides a considerable heat sink.

Liquid nitrogen is not scarce, only a little obscure. Food
processing plants make and use a lot of it. 5 gallons of it would
likely keep your fridge cold for weeks, if it was well insulated and
kept closed.

I do nnot know how common small Ln2 compressor are, or how available.

Liquid N2 boils and evaporates while in the dewar, dependant on it's
insulation efficiency. What comes off of the stored container is
very cold nitrogen gas. Cast off evaporated N2, still cold, could be
used to augment other air conditioning (refridgeration) systems.

I suppose this would be considered radical tech.

Terry k

??? about keeping refrigerators cold
 

??? about keeping refrigerators cold
 

On 14 Jul 2004 16:42:12 -0700, (Richard
Kollmann) wrote:
The way that this problem is normally solved is by adding a standard
icebox 12 volt conversion unit in the existing refrigerator.

===============================================

This is a good solution for the refrigeration business, and in
fairness, does provide some redundancy. The easy and cost effective
solution however is to use an inverter. WalMart is selling a nice
little 700 watt unit (1400 watt peak) for less than $80. I tried it
on my full size home fridge the other day and it ran fine, pulling
down less than 20 amps from a pair of golf cart batts (Sam's club, $45
each). On my old boat I ran a full width under-the-counter fridge
from an inverter. Average 12 volt draw draw was well under 10 amps.

??? about keeping refrigerators cold
 

wrote in message
...
I have a large refrigerator and don't want to get rid of it since I'm
on the boat a lot, and the majority of the time at the dock. But do
like to go out for a couple of days each week, and the biggest
issue is the frig getting too warm unless the generator runs more
than I like it to.


My suggestion would be to get an inverter and battery bank that would run it
while you were away from the dock.

I assume that by "large" you mean a standard household, frost free unit.
These things can be real pigs on energy use, as most use as much energy
heating things (and I don't mean the byproduct of cooling) as they do on the
compressor.

A typical frost free refrigerator has

1) a heater around the door sill (open the door, put you hand against the
spot the rubber gasket would rest: it's warm, isn't it?)

2) A heater on the cooling coils, which is energized on a periodic basis to
melt the ice that forms

Many refrigerators also have a heater under the drip tray to evaporate the
water that collects from the defrost cycle!

A non-frost free refrigerator would require about 100 amp-hours a day to
keep things cold. A regular frost free unit would probably require twice
that. If you installed an inverter and a 200 amp-hour battery (two golf
cart batteries in series) and then ran your generator for a few hours each
day you could probably get by for two or three days.

Rod

??? about keeping refrigerators cold
 

I have to go along with the inverter and a decent house battery bank. I
have an 8 cu ft household refrig on boart and run it off the inverter
whenever under power, and can run it about 12 hours (in several 3 hour
stretches) over 2 days. Once packed with food, they keep pretty cold by
themselves - I still have ice in the trays after overnight without power. A
bit of judicious power management makes everything work well.

Jim
"Rod McInnis" wrote in message
...

wrote in message
...
I have a large refrigerator and don't want to get rid of it since I'm
on the boat a lot, and the majority of the time at the dock. But do
like to go out for a couple of days each week, and the biggest
issue is the frig getting too warm unless the generator runs more
than I like it to.


My suggestion would be to get an inverter and battery bank that would run
it
while you were away from the dock.

I assume that by "large" you mean a standard household, frost free unit.
These things can be real pigs on energy use, as most use as much energy
heating things (and I don't mean the byproduct of cooling) as they do on
the
compressor.

A typical frost free refrigerator has

1) a heater around the door sill (open the door, put you hand against the
spot the rubber gasket would rest: it's warm, isn't it?)

2) A heater on the cooling coils, which is energized on a periodic basis
to
melt the ice that forms

Many refrigerators also have a heater under the drip tray to evaporate the
water that collects from the defrost cycle!

A non-frost free refrigerator would require about 100 amp-hours a day to
keep things cold. A regular frost free unit would probably require twice
that. If you installed an inverter and a 200 amp-hour battery (two golf
cart batteries in series) and then ran your generator for a few hours each
day you could probably get by for two or three days.

Rod

??? about keeping refrigerators cold
 

The down side is that if you have a modified sinewave inverter (the
typical cheap ones), the compressor may run hot and its lifetime
shortened by many years. A true sinewave inverter does much
better but then again costs alot more. It's a tradeoff as usual.

Doug
s/v Callista

"Marie Rabey" wrote in message
...
I have to go along with the inverter and a decent house battery bank. I
have an 8 cu ft household refrig on boart and run it off the inverter
whenever under power, and can run it about 12 hours (in several 3 hour
stretches) over 2 days. Once packed with food, they keep pretty cold by
themselves - I still have ice in the trays after overnight without power.
A
bit of judicious power management makes everything work well.

Jim
"Rod McInnis" wrote in message
...

wrote in message
...
I have a large refrigerator and don't want to get rid of it since I'm
on the boat a lot, and the majority of the time at the dock. But do
like to go out for a couple of days each week, and the biggest
issue is the frig getting too warm unless the generator runs more
than I like it to.


My suggestion would be to get an inverter and battery bank that would
run
it
while you were away from the dock.

I assume that by "large" you mean a standard household, frost free unit.
These things can be real pigs on energy use, as most use as much energy
heating things (and I don't mean the byproduct of cooling) as they do on
the
compressor.

A typical frost free refrigerator has

1) a heater around the door sill (open the door, put you hand against
the
spot the rubber gasket would rest: it's warm, isn't it?)

2) A heater on the cooling coils, which is energized on a periodic basis
to
melt the ice that forms

Many refrigerators also have a heater under the drip tray to evaporate
the
water that collects from the defrost cycle!

A non-frost free refrigerator would require about 100 amp-hours a day to
keep things cold. A regular frost free unit would probably require
twice
that. If you installed an inverter and a 200 amp-hour battery (two golf
cart batteries in series) and then ran your generator for a few hours
each
day you could probably get by for two or three days.

Rod