Date: Sun, 22 Jul 2007 11:52:43 -0700
Reply-To: Michael Elliott <camping.elliott@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Michael Elliott <camping.elliott@GMAIL.COM>
Subject: Re: Where is The Heat Going?
In-Reply-To: <86476e250707220723x7b86c2dub508231983eae1ef@mail.gmail.com>
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Loren Busch typed:
> RE: Heat Dissipation
>
> One of the more interesting things to come out of this thread is, in one of
> the links, I think provided by Dennis, Dometic emphasizes that if the
> interior temp of the vehicle goes to high or the ambient air goes to high
> the cooling decreases to the point of no cooling and even possible damage
> to the refrigerator. This is no surprise, consistent with the results so
> many of us have seen. And also supports the improved results seen by some
> by adding a forced air exhaust fan to get rid of the hot air behind the
> refrigerator.
>
That would be the link that Chris C provided
( http://www.bdub.net/manuals/DometicBulletin12-87.pdf ) which says that
if the air temp in the van (presumably what they mean is the temp behind
the refrigerator where the cooling unit lives) exceeds 100 (F) then the
"cooling process will slow down or stop completely."
In other words, the Dometic 182 can hold the 40 to 45 degree temperature
differential* that I and others have measured as long as the air temp
around the cooling unit is below 100F. After that, the refrigeration
simply stops.
Later in the bulletin, they write that if the refrigerator does not pass
testing if the air temp is above 90F, it "may indicate a restricted
air flow [behind the refrigerator]." So 90F rather then 100F is when the
cooling unit is feeling the heat.
So my guess (and I wish I had an industrial oven to place the unit into)
is that when the rear temp is less than 90F, the Dometic can hold its
internal temp 40-45F less. Between 90 and 100F, the differential gets
smaller as the cooling unit begins to lose efficiency. Once above 100F,
the cooling unit no longer cools at all.
Those of you who like to make measurements and have Dometics, how about
sticking a thermal sensor behind the refrigerator and one in the van and
reporting how the temp (gas vs electric, what the heck) back there
compares with the ambient temp?
-------
* As Dennis says, these are old refrigerators. Some of us may have
"weak" ones, some may have "strong" ones. If you're scratching your head
wondering what the fuss is about because your food and beverages are
always nice and cold, you may have a "strong" one. Or maybe you camp in
cooler environments, or have a more generous assessment of what is
sufficiently cold. Hard to say unless you can do as Jake suggested:
measure your van's internal temp and the temp inside the reefer on a hot
day. If it's running 70F outside and you have 30F inside the reefer,
then no big deal, this is well within the operating characteristics of
the refrigerator. On the other hand, if it climbs above 90F at noon and
stays there until evening, yet the refrigerator's temp stays more than
45F below the temp in the van (or, better yet, near the cooling unit),
then you might have a "strong" unit.
--
Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
KG6RCR
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