Date: Fri, 7 Sep 2007 17:45:39 -0700
Reply-To: neil N <musomuso@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: neil N <musomuso@GMAIL.COM>
Subject: Re: Dometic in 100F ambient?
In-Reply-To: <6BBD92CF-8918-431C-826B-78DAD1EE4641@xochi.com>
Content-Type: text/plain; charset=ISO-8859-1
On a recent trip, I found that my Dometic 182A, with thermostat turned
all the way up, ran hot all the time. i.e. the rear fan was on almost
all the time. Regardless, inside temps were pretty cool. The lowest
being 20F (!) on a coldish night to 43F in mid 80 - high 90's F. This
was with thermostat set to 12:00 or "max" all the time.
On LP, the combustion chamber itself gets pretty hot. So does the
exhaust tube. Both will contribute heat. In really hot ambient temps,
with thermostat set to "max", the flame in burner is likely on the
large "setting" almost all the time. This will obviously produce a lot
of heat.
On AC, there is obviously no LP burning, so heat comes mainly from the
"coolant" tubes on fridge containing the ammonia etc. (as it also does
on LP) It's possible a little heat is transferred from the "coolant"
to the exhaust tube contained in the insulation. If so, and I'm
guessing here, it would be very little.
At one point, I thought the "coolant" tube on mind had seperated from
the exhaust tube. It hadn't. There's at least a few spot welds holding
the coolant tube to the LP exhaust tube. It's possible that in
servicing the Dometic, the amatuer might spread the exhaust tube and
"coolant" tube too far apart, but that would take some doing IMHO. And
likely welds would hold.
Neil.
On 9/7/07, Michael Diehr <md03@xochi.com> wrote:
> Dometic update:
>
> First, see my other thread in which I issue an apology to my poor
> dometic -- turns out the propane tank was running on fumes and that
> was causing much of the weird dometic behavior.
>
> Second -- after filling with propane, I had a chance to run the
> dometic in a week's very hot (up to 110F) temperature. I was
> actually pleasantly surprised by its performance. It was able to
> keep the interior around 41-45 degrees most of the day, only creeping
> up to the 50s in the mid-day heat.
>
> Third, and I think most interesting -- I had the chance to plug into
> AC power for a few days and turn off the propane. On AC I found the
> dometic worked slightly better than on propane in terms of internal
> fridge temperature. But the biggest difference was in the amount of
> heat dumped in the cabin -- If I had to guess, I'd say that running
> on propane dumps 5x or 10x more heat into the vanagon cabin than
> running on AC.
>
> Question -- since the fridge seemed to work great on AC, but dump an
> incredible amount of heat into the cabin on propane, I'm wondering if
> it's possible that the heat coupling between the propane flame and
> the fridge has come loose or is otherwise degraded, causing the
> fridge to run the flame on high 24/7 to get as much heat transfer as
> possible. Is this a possible failure mode?
>
> -mike
>
>
> On Aug 16, 2007, at 5:38 PM, Alistair Bell wrote:
>
> > Ah the dometic threads, such a sign of summer :)
> >
> >
> > Its not coincidental that I have been thinking about the Dometic a
> > lot recently, what with brainstorming with fellow list member P.
> > Chubbuck and adding some stuff to the vanagonwiki. I have, and many
> > other's too, posted temp data and modifications to the stock fridge
> > ( i understand that record of the list's emails are collected and
> > organised in some sort of "Archive"), and in the last 2 days I have
> > tried couple more things.
> >
> > 1. I replaced my little muffin fan on "icebox" grill with a littler
> > and quieter one (intel branded CPU cooler). the interior fan is good
> > mod. I recorded some fridge temps after the mod, remember this is
> > Victoria BC , not Tuscaloosa, so ambient temps are more civilised. I
> > kept the van closed tight, new interior fan on, fridge empty.
> >
> >
> > time fridge temp van temp elapsed time notes
> > 18:00 27.4 25.7 0
> > 18:10 28.1 26.8 10
> > 18:15 25.7 27.1 15
> > 18:20 23.5 27.4 20 back fan on
> > 18:30 19.7 27.4 30 back fan on
> > 18:55 12.1 28.2 55 back fan on
> > 19:05 9.9 28.1 65
> > back fan on
> > 19:11 9.0 28.1 71
> > back fan on
> > 19:32 6.6 27.8 92
> > back fan on
> > 19:44 5.6 27.6 104
> > back fan on
> > 19:57 4.8 27.4 117
> > back fan on
> > 20:10 4.1 26.9 130
> > back fan on
> > 20:23 3.6 26.5 143
> > back fan on
> > 21:05 2.2 24.8 187
> > back fan on
> >
> >
> > not bad performance. the back fan is a muffin fan i used to replace
> > the stock fan. I have to admit it is not as efficient as the stock
> > fan, it stay on more, doesn't cycle as much.
> >
> >
> > My set up as of yesterday also had a muffin fan (switched) attached
> > to grill on left side of stove unit, right adjacent to the stowage
> > bins. You can feel the waste heat from the fridge come out there. I
> > (and I think others) thought a fan there would help cool the back
> > coils of the fridge. I think it does but, in the summer, that hot air
> > now blowing rather than convecting is not cool :)
> >
> > this afternoon i had the chance to pull the fridge out of the van to
> > give it a once over. I had left the fridge running after my temp
> > recording expt and found next morning the flame had gone out. I
> > wondered if the by-pass jet in the thermostat control had plugged or
> > maybe it was a combustion chamber problem. Turned out I was out of
> > gas.
> >
> > But i pulled the fridge. The by pass jet was clean. The combustion
> > chamber was dirty. fine metallic dust, which looks like it was coming
> > from the inlet and exh. pipes. I blew the pipes out with compressed
> > air, blew the main jet, sealed the cracked grommets where the
> > thermoprobe and piezo connect. I also removed the side grill fan and
> > did the mod to the city water access port, adding a switched muffin
> > fan. So instead of a fan just pushing hot air faster into the cabin,
> > i have a fan pushing the hot air out of "flapped" city water port.
> >
> > That port mod looks like a winner, hats off to the list-members that
> > invented it.
> >
> > Alistair
> >
> >
> >
> >
> >
> >
> >
> > '82 westy, diesel converted to gas in '94
> > http://www.members.shaw.ca/albell/
> >
> > On 16-Aug-07, at 1:47 PM, neil N wrote:
> >
> > Hi Todd.
> >
> > just thought i'd throw in my .02 here.
> >
> > Have been in mid 80's to 90 F weather in B.C. interior. Temps in van
> > slightly higher. Fridge has maintained (when driving, or at camp with
> > open
> > slider door) low 40's and down to 28 at night. (it's much cooloer
> > outside at
> > night) When I parked a the mall here, it was 86. Fridge is at 39.
> >
> > I have found an average of 40F differential.
> >
> > I have a 5" fan in place of stock fan at rear, and of real use an
> > internal
> > CPU fan. FWIW the thermal has the rear fan on almost all the time,
> > but of
> > course fan is switchable.
> >
> > Also of note I did a lot of maintenance/trouble shooting recently, so
> > this
> > has helped with efficiency.
> >
> > Neil.
> >
> >
> > On 8/14/07, Todd Last <rubatoguy@comcast.net> wrote:
> >>
> >> Isn't it a fact of the design of the Dometic (or any ammonia
> >> apsorption
> >> fridge) that you are not going to get any better than 20-30
> >> degrees lower
> >> than the ambient temperature?
> >>
> >>
> >> Todd
> >> '88 Westy
> >>
> >>
> >> -------------- Original message ----------------------
> >> From: Michael Diehr <md03@XOCHI.COM>
> >>> After this last weekend's positive experience with a coleman xtreme
> >>> cooler in 100F+ temperatures, I'm wondering if there's even any
> >>> reason trying to fix up the Dometic.
> >>>
> >>> First question -- has anyone ever had a working dometic provide
> >>> adequate cooling in 100F+ temperatures?
> >>>
> >>> Looking at the coleman cooler, I notice that it has almost 2" of
> >>> foam
> >>> insulation. Looking at the dometic, it seems to have very little
> >>> insulation, and it also seems to be self-defeating as it dumps so
> >>> much waste heat under the cabinet, so it's basically bathing itself
> >>> in hear.
> >>>
> >>> Second question -- is re-insulating the dometic with some sort of
> >>> modern insulator a possibility?
> >>>
> >>> Third question -- does venting the waste heat out of the van make a
> >>> serious difference? The dometic has a fan already, but all it seems
> >>> to do is stir up the air behind the cabinet. Would a fan that
> >>> vents
> >>> the air outside of the van actually be better?
> >>
> >
> >
> >
> > --
> > Please send me your Vanagon/Westfalia links!
> > http://vanagonlinks.googlepages.com/home
> >
> > Neil Nicholson. 1981 Air Cooled Westfalia.
> > http://web.mac.com/tubaneil
>
--
Neil Nicholson. 1981 Air Cooled Westfalia -
"Jaco" (Bustorius)
http://web.mac.com/tubaneil
Please send fav Vanagon/Westfalia links to me at:
musomuso1963@hotmail.com
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