I have probably spent to much time working with PID and fuzzy logic
controllers. :-) There is so many sophisticated off the shelf industrial
process controllers these days I can see the day when we will see a marine
refrigeration controller that will do a lot more than we can think of.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

wrote in message
ups.com...
Glenn, You want a climate control for a jet aircraft that has
anticipators to make a correction in advance of the actual temperature
change. Heat transfer in a box is slow because static air is the
conductor from the heat source to the evaporator, where heat it is
drawn away by a small compressor. Frigoboat's SSC will give you
every thing you need but you my need to switch to manual and advance
speed before adding a large volume of warm product. I have included a
number of gadgets in my 12 volt book that can shorten the reaction time
by, increasing airflow across evaporator, starting compressor or
speeding it up when a charging voltage above 13.2 is present. You
don't need a holding plate in a refrigerator to store surplus energy,
product in the box and the box itself can store one Btu per degree per
pound, of material. In a freezer when the product is already frozen
additional energy stored is only ½ a Btu per degree per pound or 144
Btu per pound added when when the phase change from a liquid to a solid
occures.


....

On Sun, 12 Mar 2006 11:45:50 -0500, "Glenn Ashmore"
wrote:

I have probably spent to much time working with PID and fuzzy logic
controllers. :-) There is so many sophisticated off the shelf industrial
process controllers these days I can see the day when we will see a marine
refrigeration controller that will do a lot more than we can think of.

Glenn, following along in this discussion, it sounds like you picked
an evaporater unit instead of a holding plate system. If so, I'm
curious why you did that. Perhaps my situation is different because I
have a large generator available, but I really like the idea of only
needing to run the compressors for a few hours per day.

I tossed the holding plate/evaporator question around for several years
before settling on evaporators. Holding plates do have an advantage in that
they only have to be frozen down once or twice a day but that can also be a
disadvantage because it ties you to the boat. Evaporators are more or less
self maintaining so with a large enough battery bank and some alternate
energy sources we will be able to venture ashore for longer periods and fly
home for a week or so to visit the grandchildren without having to worry
about the refrigerator. Evaporators also tend to hold a more constant box
temperature and you are not limited to the single temperature that a holding
plate is designed for.

I also like ice in my drinks and remote undeveloped anchorages (if you can
find one anymore) and evaporators do a better job of making ice.

When I started looking evaporators were the cheaper alternative and holding
plates were the energy champs. That is not totally true anymore. The
little Danfoss compressors and controls have gotten a lot more efficient
over the past 5 or 6 years and with a couple of solar panels, bigger banks,
and the charging system they require a well designed evaporator system can
actually cost more.

I have attempted to set my systems up so that in normal use I can charge
batteries and make water for about 90 minutes every other day. Time will
tell how well it works out but evaporators just turned out to be the better
option for the way we plan to use the boat.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Wayne.B" wrote in message
...
On Sun, 12 Mar 2006 11:45:50 -0500, "Glenn Ashmore"
wrote:

I have probably spent to much time working with PID and fuzzy logic
controllers. :-) There is so many sophisticated off the shelf industrial
process controllers these days I can see the day when we will see a marine
refrigeration controller that will do a lot more than we can think of.

Glenn, following along in this discussion, it sounds like you picked
an evaporater unit instead of a holding plate system. If so, I'm
curious why you did that. Perhaps my situation is different because I
have a large generator available, but I really like the idea of only
needing to run the compressors for a few hours per day.