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Old 09-12-2008, 12:45   #16
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Sorry Richard, I mixed up a thin plate evaporator with condenser.Knowing that does what I've suggested make any sense? I hope you excuse me, I'm just getting into this.
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The condenser is located outside the refrigerated area where it condenses the high pressure gas to a liquid by removing its process heat. A holding plate is a form of evaporator and is less efficient than a standard thin plate evaporator because it is not as good of a heat conductor as the evaporator. Eutectic solution holding plates are only used to store surplus energy the same as a battery. Surplus energy for holding plates must come from a very large compressor, one half HP or larger, or from extended hours of alternative electrical power wind or solar for use in runing a small refrigeration compressor.

Selecting the correct equipment and compressor speeds for 12 volt refrigeration is the key to good performance and energy efficiency. Poor equipment selection could mean you will receive only 30 Btu of cooling for each amp-hr consumed.
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Old 09-12-2008, 13:55   #17
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I was aware of the variable speed capability, however, is it possible to set the system up with one of the new condensors such that in the day time (and thus hotter), it is possible that the unit automatically selects a higher speed?
The Frigoboat (Danfoss K35 compressor) system on my boat has a digital controller that drives the compressor speed. I can manually override it to run the compressor at higher speeds. The controller works to a temperature setpoint, though. When the sensor in the box detects that the setpoint has been reached, it slows down the compressor.

So, you could adjust the setpoint, or manually force the compressor to run fast during periods when you have abundant electricity.
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Old 26-10-2009, 09:56   #18
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We have a Grunert AR-50 12V holding plate system that's worked well for 10+ years
Same system that we have....since 20 years, still working but for how long?
Any information about Grunert replacements for the compressor?
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Old 26-10-2009, 10:24   #19
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"If box temperature is maintained at the same continuous temperature Holding Plates are not as efficient as conventional Evaporators." yes listen to Mr. Kohlman. Cold plate only if you have Lots of excess energy only a couple times of day.Everything must match for max efficiency!
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Old 26-10-2009, 10:43   #20
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Charly,

Here is a link from Richard Kollmann's web site that talks about these usints. You may find some of the trhead of interest.

kollmann-marine.com :: View topic - Replacement of grunert ar50 110v compressor
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Old 26-10-2009, 20:48   #21
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Same system that we have....since 20 years, still working but for how long?
Any information about Grunert replacements for the compressor?
AFAIK, when the AR50 compressor goes, about the only remaining choice is to run one down from another system. There are no re-build kits for this puppy. Unfortunately.

BTW, the "smart" thermostat is working like a charm. It cuts way down on run time, energy waste, and holds the box's temperature much more effectively than the old mechanical thermostat.
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Old 26-10-2009, 22:03   #22
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Old 08-06-2011, 01:12   #23
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Re: 12vdc Refrigeration Confusion

found this information about Grunert AR50. We have one of these and have to replace shaft seal. Where did you get that shaft seal and do you know the compressor type used (Tecumseh ????). Is the unit working well with 409a? We still use R12 but might change to 409 or R134. Thanks for the info!! Charles

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We have a Grunert AR-50 12V holding plate system that's worked well for 10+ years, with repairs limited to replacing a thermostat (the capillary tube chafed through), motor brushes, and, just this year, a crankshaft seal. Concurrent with that repair we replaced the R-12 (ozone-hostile) refrigerant with R-409a. We'll keep the unit until it fails.

However, I've looked at possible replacements and, frankly, find more hot air and hype than solid information to base a choice on. IMHO, take the names of the units you like, put 'em on pieces of paper and tape them to the wall. Toss a dart while blindfolded and go with the name closest to the dart.
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Old 17-10-2011, 21:26   #24
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Re: 12vdc Refrigeration Confusion

Any luck finding parts or replacements for the AR50 compressor?
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Old 18-10-2011, 02:24   #25
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Re: 12vdc Refrigeration Confusion

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Any luck finding parts or replacements for the AR50 compressor?
No. We installed a SEAFROST Dc 5000 compressor R134a. Was a difficult task. Working now finally.
Charles
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