Derek, I see you are from Oz and I don't think you have the stupid
restrictions against R-12 refridgerant we do here in the states.......

Look around your area for a small fridge that uses R-12 refridgerant
and its compressor is a vibrator, not a motor. Mine is an old
pre-restriction Norcold unit that is 2' by 2' by 2.5' deep with the
external condensor arcing out the back. The compressor is easily
identified because the electrical connections to it are ONE wire to an
insulated terminal and one wire grounded to the pipes on the
compressor. This compressor uses 40VAC from a little power
transformer. The manufacturer does this so that when they ship it to
Oz, it would have a 220 to 40V transformer and to the USA a 115 to 40V
transformer.....

Now the kicker that will blow that solid state crap clear out of the
water......These fridges draw 40 watts only when running! R-12 is
very low pressure gas, why they use it in cars with rubber hoses. The
little vibrator compressor has NO STARTING CURRENT, it's simply a coil
bouncing its core up and down at 50 or 60 Hz.....connected directly to
the diaphram the pump uses to pump the gas. My old Norcold runs about
50-60% of the time at 40W....50 to 40% of the time a ZERO watts....not
that constant amp drain of the thermoelectric garbage that hardly gets
cold. The little Norcold will make THREE trays of hard ice in about 1
hour and 30 minutes, something thermoelectric won't do....

40 watts at 12V is about 3.5A about half duty cycle, depending on how
often you open it, of course. A tiny 80W inverter that's built right
into the 12V cigarette lighter plug from Radio Shack will power it
continuously! My Honda EU1000i tiny genset doesn't even vary when it
comes on it's such a light load.

Look around for one of these fridges. Way more efficient cooling and
you can hardly hear it running on forbidden R-12, or maybe the new
R-134a used in the new cars.....

Larry


Larry W4CSC

"No, NO, Mr Spock! I said beam me down a WRENCH,
not a WENCH! KIRK OUT!"

(Larry) wrote in message ...
Derek, I see you are from Oz and I don't think you have the stupid
restrictions against R-12 refridgerant we do here in the states.......

I'm unsure what restrictions there are here, but I know there are some
and my guess is they'd be similar to yours.

Thanks for your comments. I appreciate the wisdom of your advice. Were
I starting from scratch, I think I'd do as you suggest. As things are
however, I'll continue with the Peltier despite its woeful efficiency.
Stubborn perhaps, (think I'd have to grant that) but its interesting
trying to get the best possible from the Peltier.

Which leads to a couple of recent changes which hopefully may improve
things, if slightly.

Condensation has been forming on the cold fins inside the cold box.
This didn't happen previously with an internal fan, so I've just
(reluctantly) refitted a new internal fan. Its a 12 volt brushless
ball bearing unit, and with a 150 ohm series resistor it ticks along
soundlessly at a sedate but hopefully useful speed. With luck it'll
reduce condensation and last a long time.

I've noticed that the differential between ambient and cool box
temperature seems greater on days with some overcast.
In full sun the panels are capable of delivering some 6 amps at 16 or
so volts, and were driving the Peltier well past its optimum operating
point. I've just fitted a current regulator to limit the maximum
current delivered to the Peltier, and hopefully it'll eliminate the
overdriving.

Derek Weston
VK3BIJ
Talking Depth Sounder http://www.alphalink.com.au/~derekw/mit/apps.htm

In a couple of trawler and sailboat magazines, I've seen a peltier
cooler that doesn't have any cooling fins outside the box. The
junction heats up a fairly good sized copper braid (so you can bend
it) that goes to a thru-hull fitting of some solid metal the ocean
won't eat...stainless?? not sure. The idea is to have a
seawater-cooled solid state fridge which should cool the junction MUCH
better than fins in that hot engineroom or boiling bilge.....

Sorry I don't remember the company name...maybe someone else reading
this will know. Looks very interesting.



On 31 Jul 2003 15:43:16 -0700, (Derek Weston)
wrote:

(Larry) wrote in message ...
Derek, I see you are from Oz and I don't think you have the stupid
restrictions against R-12 refridgerant we do here in the states.......

I'm unsure what restrictions there are here, but I know there are some
and my guess is they'd be similar to yours.

Thanks for your comments. I appreciate the wisdom of your advice. Were
I starting from scratch, I think I'd do as you suggest. As things are
however, I'll continue with the Peltier despite its woeful efficiency.
Stubborn perhaps, (think I'd have to grant that) but its interesting
trying to get the best possible from the Peltier.

Which leads to a couple of recent changes which hopefully may improve
things, if slightly.

Condensation has been forming on the cold fins inside the cold box.
This didn't happen previously with an internal fan, so I've just
(reluctantly) refitted a new internal fan. Its a 12 volt brushless
ball bearing unit, and with a 150 ohm series resistor it ticks along
soundlessly at a sedate but hopefully useful speed. With luck it'll
reduce condensation and last a long time.

I've noticed that the differential between ambient and cool box
temperature seems greater on days with some overcast.
In full sun the panels are capable of delivering some 6 amps at 16 or
so volts, and were driving the Peltier well past its optimum operating
point. I've just fitted a current regulator to limit the maximum
current delivered to the Peltier, and hopefully it'll eliminate the
overdriving.

Derek Weston
VK3BIJ
Talking Depth Sounder http://www.alphalink.com.au/~derekw/mit/apps.htm


Larry W4CSC

"No, NO, Mr Spock! I said beam me down a WRENCH,
not a WENCH! KIRK OUT!"

(Larry) wrote in message ...
In a couple of trawler and sailboat magazines, I've seen a peltier
cooler that doesn't have any cooling fins outside the box. The
junction heats up a fairly good sized copper braid (so you can bend
it) that goes to a thru-hull fitting of some solid metal the ocean
won't eat...stainless?? not sure. The idea is to have a
seawater-cooled solid state fridge which should cool the junction MUCH
better than fins in that hot engineroom or boiling bilge.....

Sorry I don't remember the company name...maybe someone else reading
this will know. Looks very interesting.

Yes, that's a very good system for cooling the junction while it's
powered, but it doesn't thermally isolate the junction (hence cool box
internals) while the Peltier is depowered. I really need the thermal
isolation you get with a thermosyphon (or some other) setup as the
solar powered Peltier typically runs only around eight hours a day.
Loss of "cold" overnight via the Peltier was a real problem with the
original air cooled arrangement.

Our cooling zig-zag in the engine compartment duct actually works
quite well, as that duct goes to the bottom of the engine compartment.
When the engine is running, air is dragged in through the duct from
abovedecks by virtue of the engine's aspiration, helping cool the
zig-zag. After the engine has been running, the thermally induced
airflow in that duct is from the outside in as the engine compartment
also has high level vents. When the engine is cold it seems there's
enough air movement in the duct to cool the thermosyphon return water
to only a few degrees above ambient.

Still, a few degrees above ambient air temp is often quite a few
degrees above seawater temp.

If there was an easy (moving-parts-free) way to combine a thermal
"diode" or "switch" with seawater cooling then that could be ideal,
but that'd be a bit difficult on my boat as the Peltier is above the
waterline.