At 14:51 5/8/2000, BRENT CHRISTENSEN wrote:
> > 3) What is the purpose of 'burping' the fridge??? Is this
> > going to help me or
> > does the fact that the fridge works on
> > AC mean this in unnecessary.
>
>I believe this has something to do with the ammonia compound that is used
>as a "refrigerant" settling into a crystalline form after time and lack of
>use.  It helps to resuspend and mix the solution that the system relies on
>to carry the heat through the system.

The refrigerant is a mixture of water, hydrogen, and NH3 (ammonia), with
some sodium chromate (anticorrosive) in solution, the whole under about 350
psi pressure.  When in operation, the various parts of the system have
differing proportions of all the gaseous elements -- water vapor, hydrogen,
ammonia.  [Quoting from Dometic service bulletin:]  If the system has been
overheated by being operated off-level or with inadequate ventilation, the
ammonia solution in the boiler becomes too weak to support the cycle, and
refrigeration stops.  To remedy this, let reefer cool down completely,
remove it and invert it several times.  This will remix the solutions.

Dometic also recommend to tip the reefer to right, left, front, back
anytime before reinstalling -- they say this will ensure that the cycle
starts up as promptly as possible.

The other issue of off-level operation is that if the boiler goes dry, the
sodium chromate will come out of solution and be baked onto the boiler
walls, interfering with heat transmission and ultimately clogging the
boiler.  The whole operation cycle, including the problem just mentioned,
is very well described and illustrated at:
http://www.rvmobile.com/Tech/Trouble/cooldoc.htm
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"