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?

No shore power at the dock?

You could fill the freezer section with "Blue Ice" bags and then take them out
of the freezer and put them in the refrigerator portion when you shut down, but
that won't be anywhere nearly as effective as running the compressor and
evaporator.

It sounds like you have an AC refrigerator,
no shore power, and you're setting the boat up to run your AC generator to keep
the beeer cold?

Or you've got a dual voltage refrigerator and the genset is running to recharge
your house bank?

A little more information might get you more helpful responses.

On 14 Jul 2004 15:45:54 GMT, (Gould 0738) wrote:

No shore power at the dock?

Yes there is shore power, and since I'm there the majority of the time
don't want to get rid of the nice big frig because it's so convenient.

You could fill the freezer section with "Blue Ice" bags

That sounds like the type of thing I'm hoping to learn more about.
If you'd care to tell me a bit more I'd appreciate it. Meanwhile I'll see
what Google has to offer.

and then take them out
of the freezer and put them in the refrigerator portion when you shut down, but
that won't be anywhere nearly as effective as running the compressor and
evaporator.

It sounds like you have an AC refrigerator,
no shore power,

It's an AC refrigerator, and AC shore power the majority of the time.

and you're setting the boat up to run your AC generator to keep
the beeer cold?

If it was just beer I'd only have to fool with an ice chest. But it's beer
plus everything else...including frozen food that I'd like to keep as well
frozen as possible.

Or you've got a dual voltage refrigerator and the genset is running to recharge
your house bank?

If I can get the frig to stay cold longer, I can greatly cut down on the
time that the generator has to run, the number of times it has to be started
and stopped, the amount of gas it uses, the number of times it has to be
re-fuled, and how much time I have to spend hearing it run.

A little more information might get you more helpful responses.

Thanks for any help people can give!

wrote:

If I can get the frig to stay cold longer, I can greatly cut down on
the
time that the generator has to run, the number of times it has to be
started
and stopped, the amount of gas it uses, the number of times it has to be
re-fuled, and how much time I have to spend hearing it run.


You might be able to cut down on the number of times the generator
has to run, but I don't think you'll be cutting down on the about of
gas it uses, # of times to re-fule, or the general efficiency. It will take
that generator/refrigerator combo some specific amount of fuel and
time to cool that fridge & it's contents. Adding things like freezer
bricks will just mean it runs longer to cool/freeze them. Then, once
cold/frozen, the refrigerator may not have to be started again.

There is, I'm told, some efficiency advantage to having more
items (mass) in the refrigerator. I believe that's because they
will accept & hold the cold better than air will.

The other line of thought here is...can you make the refrigerator
more efficient by adding insulation around it. You probably
don't have room for that on a boat, but it's a thought. Another
idea: if that unit is old and/or not keeping it's cool maybe a
new unit will be more efficient at generating & keeping cool

Obvious but...the less times you open the door....

Good luck.

On Wed, 14 Jul 2004 16:06:14 GMT, wrote:

[snip]

If it was just beer I'd only have to fool with an ice chest. But it's beer
plus everything else...including frozen food that I'd like to keep as well
frozen as possible.

Or you've got a dual voltage refrigerator and the genset is running to recharge
your house bank?

If I can get the frig to stay cold longer, I can greatly cut down on the
time that the generator has to run, the number of times it has to be started
and stopped, the amount of gas it uses, the number of times it has to be
re-fuled, and how much time I have to spend hearing it run.

I'm confused. If you're connected to shore power, why would your generator ever
have to kick on? Do you not have some sort of battery tender?

I agree with the suggestions regarding "blue ice" or some equivalent; a
refrigerator is just a heat exchanging device, and allowing some heat exchange
to occur *inside* the box (using blue ice) will help offset the exchange from
inside the box to the outside.

Joe Parsons

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

Joe Parsons wrote:

I'm confused. If you're connected to shore power, why would your
generator ever have to kick on? Do you not have some sort of battery
tender?

I think what he's saying is that it's connected to shore power while he's at
the dock, and that's fine. But when he takes it out on the water for a
couple of days, he has to use a generator to power it, since it's AC only.

It seems to me that blue ice would do the trick. It would get thoroughly
frozen while at the dock (with shore power) and then the fridge would just
act like an ice box while out on the water. If he was out long enough that
the blue ice all melted and he needed to power the fridge again, he'd have
a choice: Leaving the blue ice in the fridge would mean it would take
longer (more fuel) for the generator-powered fridge to refreeze everything,
but he could go longer before having to power up the generator again.
Taking the melted blue ice out of the fridge would make cooling the
contents easier (more efficient), but he'd have to do it again sooner.

Of course, if he has enough blue ice, and he's only disconnected from the
dock for a couple of days at a time, he may never have to fire up the
generator. More insulation would help, too.

Shawn.

Just curious... are propane refridgerators legal on boats? We use them in
outposts in Canada every year and they work very well. I never see them in the
US.

I have the same situation & I use an inverter that keeps the fridge cold for
hours - then I run the generator to charge the batteries. Works great for
me.
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. 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?

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




obull (CCred68046) wrote in message ...
Just curious... are propane refridgerators legal on boats? We use them in
outposts in Canada every year and they work very well. I never see them in the
US.