Date: Wed, 15 Aug 2012 17:15:41 -0400
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: Dometic failure on propane, one time
In-Reply-To: <20120815133709.H0I63.1227019.imail@eastrmwml208>
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At 01:37 PM 8/15/2012, Dave Mcneely wrote:
>David, all your reasoning makes sense. One question about VW and
>Westfalia's intentions regarding use (which either of us can only
>infer from instructions given in published materials): If the
>expectation was (and I include Dometic in the expectation, since it
>is their machine) that the refrigerator run on gas underway, then
>what is the D.C. mode there for?
Frankly I don't think they thought about it at all. They (Westfalia)
asked Dometic for the smallest RV fridge ever made, and Dometic (who
built the full-size gas fridge I grew up with in the summertimes,
that was recalled for monoxide problems 25 years after the last one
was built) built them one. Traditionally their (and I think all) RV
fridges regardless of size are either AC/DC or AC/DC/Gas. The cost
of the DC heater and changeover switch is practically nothing in
context of the entire fridge, takes no additional space etc; whereas
the gas setup adds considerably to cost and complexity. I'm willing
to bet a nickel on spec. that the very first such fridge was a gas or
kerosene domestic (and probably Dometic) unit that some user pasted
an electric heater on to.
To me the value of the DC (or AC from an inverter) would come if you
were in a situation where gasoline was readily available but LP was
scarce and difficult to come by. In Scotland, for example, where my
'84 spent its first seven years at a US Navy spy facility in Edzell
(three miles from the Old Fettercairn distillery, if you like lowland
malts) the only propane supply my sister and her husband knew about
was a taxi company in Arbroath or some such, quite some distance away
and with their filling facility on a steep driveway so you could
never get even half a fill in the Westy's fore-and-aft mounted
tank. Out in the thules somewhere I could see a situation where you
wanted to squeeze out every single drop of LP while traveling.
>I always close the external valve when moving.
There's no question that that's incrementally safer given the stove knobs.
> And I wonder why the stove valves do not have a positive click
> stop position for off, one that would resist any unintentional
> opening of the valve. Seems only a reasonable precaution. But I'm
> not an engineer, nor do I play one on T.V. (or in techno babble videos).
Engineering fail or specification fail. Everything about those
valves is great for smooth and easy operation, and they do have a
positive off position - you cannot turn them on without pushing them
in first. But they're too easy to push even for small children, the
knobs are too close to children given that fact, and they're not
adequately protected from loads either entering through the side or
sliding along. At sea they would be a disaster. And of course
anyone can add a positive fail-safe by adding a fixture that slides a
fork behind the hub of the knob so it can't be pushed in.
>Your idea of modifying the refrigerator door to expose the controls
>is interesting. I have wondered why the controls were not made
>accessible with the door closed.
Trying to remember whether the full-size Dometic in my brother's
motorhome is built that way. It's a standalone unit with its own
doors. On these guys the finish door was left up to Westfalia, so it
was their call. A plywood door with two big rectangles routed out of
it is more expensive and weaker than one without, and even with the
vinyl edging I suspect it would look less elegant. The available
dimensions are very small IIRC for making a door that completely
misses that panel - not enough room for the nice radiused corners.
People with bigger units don't/don't have to spend all their time
fooling with them. They have more stuff in them to keep the cold,
and more room around the edges for decent insulation, and less
surface area per volume, and if they're running off DC probably can
do it for 24 hours without caring much. And they vent their
operating heat to the outside. Our little guys are fighting against
all the odds. I'll bet one major reason why Frank's new fridge works
so much better and is bigger inside is the more recent research into
high-efficiency insulation for home fridges and other
applications. I don't know whether aerogels have made it down out of
the price stratosphere yet, but I believe they're fantastic
insulators. When you're building your marine reefer system these
days (they're mostly all built into the vessel from scratch, at least
for reasonable size cruising boats) if you're feeling fancy you can
even get evacuated insulation panels that are built like a Dewar
flask. Quite spendy, but not just for the ridiculously
rich. Several hundred dollars a panel IIRC.
Yours,
David
