Date: Sat, 17 May 2003 14:00:36 -0400
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: 12V substitutes for OEM Dometic refrigerator / fridge?
In-Reply-To: <Law10-OE34qHofRVvd50001664d@hotmail.com>
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At 11:51 AM 5/17/2003, vw_traveler wrote:
>I don't know if I am potentially espousing heresy, but the OEM
>refrigerator affords little cooling power on battery power, which is
>mostly the way I use it. It's not a lot better on shore power. There seem
>to be a number of 12V coolers on the market that have improved cooling
>technology. Has anyone tried replacing the Dometic with a 12V only fridge,
>such as the Igloo Kool Mate 40?
>
>http://www.igloocoolers.com/products/active/kool_mate_40.html
I would expect coolers like this to give fairly similar performance to a
Dometic in good condition. They have similar rated temperature drop
against ambient (because of the difficulty of keeping the heat from the hot
side of the Peltier device from leaking back to the cold side), and they
use noticeably less power doing it. They have external and maybe internal
fans that run continuously when the unit is actively cooling, and I *think*
that in general they cool continuously. High-quality insulation will
reduce the run-time if there's a thermostat, but it won't get the box any
colder. They do start cooling immediately, unlike the absorption units
that take 20 minutes to start up; and likewise they aren't affected by
vehicle motion which the gravity-driven absorption systems definitely are.
If you want seriously good performance you're going to need a
compressor-driven system, and for decent efficiency (much better than
either absorption or Peltier coolers) one of the new breed like
http://www.sundanzer.com/PDF/SunDanzer_Batt_Powered.pdf -- though of course
those particular units are much too large. There are good smaller units if
you look around -- a number from Australia I think.
Finally, for decent results with the Dometic on DC you need to arrange to
keep it running during brief stops so the absorption cycle doesn't
stop. Also control the van inside temp since that's the ambient temp that
you're getting your 40-degree drop from -- this includes keeping the area
of the side of the van outboard of the fridge out of the sun. All these
small units have very limited ability to move heat, so they recover very
slowly from having a load of warm groceries shoved in them -- pre-cooling
highly advisable if possible. Finally, wiring quality makes a big
difference at 12v, and Westalia was sorta skimpy -- increase wiring size
including ground, and make sure fuse clips are clean and making good
contact to get minimum voltage drop between the battery and the fridge. It
is possible to rewire the thermostat so you can switch between AC control
(direct) and DC control (through a relay so you don't beat up the
thermostat contacts).
david
--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"
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