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Date:         Sat, 8 Jul 2006 13:05:06 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Another Dometic Problem, Archives searched
Comments: To: Ian Allan <ian.allan@BMTS.COM>
In-Reply-To:  <50be056bd25cf35626ff8ef17c353443@bmts.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 01:52 PM 7/7/2006 -0400, Ian Allan wrote: >Yup, I searched the archives; > >Recently I removed the fridge to install a new fan and upgrade the >insulation behind it. >When I installed the bracket for my fan I turned the unit upside down. >I had seen this inversion procedure recommended as a "tune up" so had >no qualms about inverting the devil.

But do make sure that the fan is blowing UP whether the fan motor is above or below the blade. That could create complications.

No harm inverting the fridge if that's what you mean. In order to operate it needs to be close to level, have correct heat input, sufficient ventilation, and high enough concentration of ammonia in the actual boiler. Running out of level or without enough ventilation will stop the absorption cycle either mechanically or thermally and result in too little ammonia in the boiler. Taking the heat off and waiting ought to cure that after a while as the ammonia diffuses but it goes faster if you invert the fridge several times to redistribute the mixture homogeneously - it will then sort itself out quickly when you fire up. There's a Dometic bulletin in the archive at <www.rvmobile.com> that addresses this.

>Upon reinstallation the fridge the cooling at first seemed far less >effective, (a great reward for my efforts) then actually seemed to >become a heating process.

Cycle stopped, then. If you run that way too long the water also leaves the boiler which leads to caking of the anticorrosive that's suspended in the mix (something-chromate, sodium maybe?), or physical cracking of one of the boiler-related parts. The first is cumulative, the second catastrophic. See rvmobile website for much info.

> After leaving the fridge on propane overnight >I noted water condensate on the outside of the vent (actually could see >some steam)

Artifact... C3H8 + 5O2 --> 3CO2 + 4H2O. Commercial LP isn't pure propane but you get the idea. Hydrocarbon combustion always has a lot of water as a product.

> and an interior temp of close to 60F. When I SHUT the >burner down the interior temperature actually went down about 6F in a >half hour as if the cooling cycle had started.

Or as if you'd taken away a 650 BTU/hr heat source...or was that below ambient? Good sign if so.

>The condensate had a >bitter salty taste.

Artifact. Large bitter dog peed on the vent etc... <g> If the cooling unit leaks you'll get ammonia stink in the area and/or yellow powder staining the point of actual leak.

>I am interested in comments but here is my real question. Has anyone >actually had success "burping" the fridge? If so how? Simply invert?

See above...you're working with water, ammonia, hydrogen and sodium chromate powder at 350 psi or so. Not very viscous unless the chromate has weird properties. Pretty sure it doesn't.

>How long? Or rotate through various attitudes in what order and for how >long. I'd like to hear from members who actually have done this. > >I know that there are far more efficient units but I would very much >like to maintain the propane cooling option and to keep the van >original.

You can diagnose the unit itself by running it on 110vac. If it works like that then there is no reason other than the actual fire for it to not work on gas. The innards have no idea where the heat's coming from. But it has to be the right amount of heat. Check out rvmobile, they have a ton of stuff including explanation and picture of how the cycle works.

d

>Thanks >Ian

-- David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/ '84 Westy "Dutiful Passage," '85 GL "Poor Relation"


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