Date: Fri, 4 Jun 2004 14:24:58 -0400
Reply-To: Tim Demarest <tim.demarest@POBOX.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Tim Demarest <tim.demarest@POBOX.COM>
Subject: Re: permanent fridge damage
In-Reply-To: <6.1.0.6.2.20040604131100.051173f0@pop1.attglobal.net>
Content-type: text/plain; charset=us-ascii; format=flowed
Thanks for the additional info... this list still rocks!
Now can anyone tell me why my fridge worked very well two weekends ago (at
Westies in the Woods in NJ, 80+ degrees F outside), but wasn't cooling
worth a darn last weekend (at Buses by the Mill in CT, outside temps only
in the 70s).
I was parked on level ground and running on propane in both places, had ice
on the fins after the first weekend, was barely getting below 50 degrees
inside the second. I find myself stumped, but will try running it a few
more times before I determine that it needs to be pulled (again).
Westies in the Woods was the first time I've ever run the fridge on
propane, and this is all after removing the fridge, cleaning all the easily
accessible parts (including the burner) and re-installing.
Tim
At 01:29 PM 6/4/2004 -0400, David Beierl wrote:
>At 12:21 6/4/2004, Tim Demarest wrote:
>>According to my source, who got it from an RV fridge repair specialist,
>>off-angle operation causes the ammonia (which acts as a refrigerant in
>>these beasts) to condense in the wrong parts of the system. Over time,
>>this can cause deposits to precipitate out of the ammonia in various nooks
>>and crannies of the system.
>
>Your informant got two things slightly mixed together:
>
>First, it's a gravity system that depends on a rather tricky combination of
>vapors and liquids -- water, ammonia and hydrogen in various combinations
>-- flowing down hill (there's a good explanation with an excellent diagram
>at www.rvmobile.com ). So when you tip it the cycle doesn't work as well,
>and if it's tipped too much things can indeed pool where they
>shouldn't. The damaging result though is that the boiler boils dry which
>causes the anticorrosive stuff to build up a hard burned cake on the side
>of the boiler. This impairs the process permanently and if it happens too
>much kills it. Either way it can only be repaired by opening the cooling
>unit, cleaning out the crud and recharging it with new working materials at
>350 psi or so. I believe the operation spec for the Dometic RM182B is +/-
>8 degrees, which is more than most (typically +/- 3 degrees one axis, +/-
>six degrees the other axis I think).
>
>When you're driving the cycle doesn't work as well because of random
>accelerations as well as hills and such, but because of the random bumps
>you don't normally have the danger of damaging the unit.
>
>
>>The recommended repair was to pull the fridge, and leave it turned upside
>>down for a few days, giving it the occasional bump and shake (not enough
>>to do damage, but enough to stir the inner fluids). This should allow
>>liquid refrigerant to get into the upper reaches of the system and
>>dissolve these deposits back into solution, resulting in improved cooling
>>once the fridge is turned upright and re-installed.
>
>Second, as I said you can't repair that kind of damage short of rebuilding
>the cooling unit. However, Dometic recommend that after servicing a
>fridge, *in order to help it establish cooling as promptly as possible* you
>should tip the unit briefly on its side -- all four sides if I recall
>correctly. This simply makes the working fluid reasonably homogenous to
>begin with so that everyone "starts square." It will soon establish itself
>in the right concentrations and places when heat is applied. It's the last
>30 seconds of this process that matter; you can do anything you want for
>the previous three weeks without measurable effect.
>
>david
>
>
>--
>David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
>'84 Westy "Dutiful Passage," '85 GL "Poor Relation"
| 
