From: Neon John <johngdnospam@bellsouth.net> Subject: Re: Recreational Vehicle Type Refrigerators Date: Wed, 28 Jul 1999 22:37:42 EDT Message-ID: <379FBE65.A1186E9C@bellsouth.net> Newsgroups: sci.engr.heat-vent-ac crebel@pop.chyn.uswest.net wrote: Funny you'd mention that. Just go through working on one. > > Does anyone have any info on these types of refrigerators; I > assume they are some type of absorption system? yep >What > typically goes wrong when they stop working? They quit getting cold? :-) >What is the > refrigerant type? Ammonia, water and nitrogen under high pressure. >Are there any Web sites devoted to this > type system? Dunno. go look. > I had one guy tell me that to fix one that isn't working you > simple remove the refrigerator from the RV and turn it > upside down for a couple of hours then reinstall > it....sounds to good to be true to me. Anyone ever heard of > this kind of refrigeration gymnastics? Well there are no moving parts inside the refrigerant loop so if all else fails, that's worth a try. Don't try to open the refrigeration system unless you'd like a bath of concentrated ammonia water under high pressure. Unless the thing rusts through and loses its charge (you'd know that if it happened), there's not much to go wrong inside the refrigeration system. These things have to be level to work. Older ones have to be REALLY level. On multi-fuel units, propane provides the most cooling, 120vac the next best and 12vdc almost none, barely enough to hold existing cold while on the road. I'd check for obstructions in the flame circuit, the flue and the ventilation ducts. The gas flame is small, little more than a large pilot light, so a large dirt dauber's nest could block the flame channel. If it will cool on gas but not on electricity, then you need to check out the electrical circuit. Most of the RV fridges are swedish made Domitec brand. If yours is a Domitec, it has the capability of modulating the gas flow to control the temperature. Make sure you have a vigorous flame on the burner. If it is barely burning, it is on minimum fire and won't do much in the way of cooling. later models have electronic controls but I'm not terribly familiar with them. but regardless, if you have heat on the boiler, and good airflow on the condenser you should get cold inside. -- John De Armond From: Neon John <johngd@bellsouth.net> Subject: Re: Frig repair--$600? Why Date: Tue, 08 Feb 2000 16:33:17 EST Message-ID: <38A08B73.9A41CDED@bellsouth.net> Newsgroups: rec.outdoors.rv-travel Windrider wrote: > > Fred thanks for the information. I will do that. I do want you to know that > I don't mind paying, I just need to feel like I am not being taken > advantage of just because I have a RV. A conventional refrigeration service shop - even if they work on large absorption systems - will have neither the specialized tools nor the techniques to work on RV absorption refrigerators. I have a lot of experience with such systems since the company I used to own commissioned large systems in nuclear power plants and for NASA. I tried recharging an RV unit once just to see if I could. To make a long story short, I couldn't, at least to achieve any meaningful cooling. The problem is the charges of ammonia, water, hydrogen and chromate are arbitrary amounts determined by the manufacturer for the specific configuration. A tech cannot make a simple measurement of pressure or temperature and know that recharging has been done correctly. I have never seen a listing of charge amounts and so anyone attempting to service the unit for the first time would be guessing. Guessing works OK for other types of refrigeration. It does not for absorption units. The second issue is, once a system is opened to air, it is likely not salvageable. Look at http://www.rvmobile.com/ and click on "rebuilding process" over on the left hand column. They don't do all that work just to run the cost of repair up. They do it because experience has shown that it is necessary in the majority of cases. IMHO, the price these shops charge for the refrigeration package, particularly if you do your own install, is quite reasonable. Even with my experience, I'd never give the slightest thought to trying to rebuild the absorption system myself or try to cheap out have have someone hack it together in their general service shop. If you've followed my posts in this group, you'll know that I'll try building or repairing almost anything. The pressure system of an absorption refrigerator is one of the few exceptions. John -- John De Armond |