Author Topic: Absorption refrigerators - a real pain!  (Read 4314 times)

Offline Barn Owl

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Absorption refrigerators - a real pain!
« on: July 03, 2011, 08:43:25 PM »
Absorption refrigerators can drive one to madness. Fired it up 24 hours ago and barely cooling. I have a 1979 Dometic that seems to freeze everything or is too warm. On occasion it works. I hope I have a dirty burner otherwise I will have to make a trip to Wal-mart and hope I can survive on a 40qt Coleman 12v cooler.  Several years ago I bought a used 12v RV refrigerator but I am not prepared to install it at this time. My thought was to beef up my battery bank in the future and make the swap. Large family = large expense eating out. Even ice gets pricy if I go to chest coolers. Any alternate creative ideas out there?
« Last Edit: July 03, 2011, 08:45:27 PM by Barn Owl »
L. Christley - W3EYE Amateur Extra
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Offline jackhartjr

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Re: Absorption refrigerators - a real pain!
« Reply #1 on: July 03, 2011, 08:46:19 PM »
If you put something under the ice cooler to lift it slightly off the floor, you will spend less than half on ice as you do now!
I found a pegboard made of plastic at K-Mart that works GREAT!
Jack
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Offline papatony

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Re: Absorption refrigerators - a real pain!
« Reply #2 on: July 04, 2011, 04:39:28 AM »
   I have a rfig. does the same thing ,I found that if I run it on gas until it gets cold it will run fine on a c from then on.. Dosen't hurt to try.  Tony

Offline desi arnaz

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Re: Absorption refrigerators - a real pain!
« Reply #3 on: July 04, 2011, 05:33:46 AM »
Check the ohms on the electric burner,yours will be lower than normal.with mine i also start her on gas and she will run fine on ac.
thomas f  Bethlehem n.h

Offline Barn Owl

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Re: Absorption refrigerators - a real pain!
« Reply #4 on: July 04, 2011, 08:45:35 AM »
Update: After beating and banging on the boiler housing a large ball of "soot" fell out of the flame chimney. About 1" diameter, it is as light as a feather, black as coal, and snaps into powder when pinched. Blew everything out with an air hose. Temps are dropping, fingers are crossed!
L. Christley - W3EYE Amateur Extra
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Offline JohnEd

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Re: Absorption refrigerators - a real pain!
« Reply #5 on: July 04, 2011, 09:02:53 AM »
Barn owl,

I suspect you have fixed it.  Look, these things have been around for eons.  You simply cannot discover that the "principle" isn't correct.  Absorption works!  I had a Dometic that was made in 73 and the reason I replaced it last year was that I had ruined the door and no replacement could be found and I looked for 5 years.  That refer never missed a beat...completely reliable....and seemed to run of the mere presence of propane tanks.  If your performance falls off have a tech look at it.  But make sure the flu is clear and that there is a flame on the burner.  If the rear isn't getting fresh air it won't work very well either.

Gas costs a lot more than a small electric.  The price differential cannot be denied.  But the delta is eaten by the inconvenience of needing a pole or big battery bank and inverter.  I have had such a very good experience with gas I wouldn't consider electric unless the compressor ran directly on DC from my bats.

I always thought that the AC feature on a RV refer was to help keep the refer cold while you went and had the gas bottle filled.  Nobody I ever talked to said that their absorption refer ran sat on AC.  Most I heard anyone say is it barely keeps the refer cold if not opened.  I can't imagine DC would be any better but I don't recall ever hearing a comment and none of mine had that option.

John
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The price of apathy towards public affairs is to be ruled by evil men." Plato
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Offline Barn Owl

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Re: Absorption refrigerators - a real pain!
« Reply #6 on: July 04, 2011, 02:02:56 PM »
Stuck at 49 degrees so I have improved it but not enough. I think I am going to manually attempt to clean out the burner flue. Any problem doing this? What is the differential cooling anyway? 90 degrees outside and humid.
L. Christley - W3EYE Amateur Extra
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Offline Len Silva

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Re: Absorption refrigerators - a real pain!
« Reply #7 on: July 04, 2011, 02:23:11 PM »
Do you have stuff in it?  An empty box will never seem to cool right.  TRY filling it with bottles of water for a couple of days and see what happens.

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Offline Barn Owl

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Re: Absorption refrigerators - a real pain!
« Reply #8 on: July 04, 2011, 08:40:36 PM »
34 degrees now, but it is also 70 degrees outside and no sun heating up the bus. So earlier I pulled the top roof cover off, ripped out the screen and vacuumed a few stink bus off the top cooling fins. It made me feel better more than it really helped the air flow. I think I can fill the interior up as earlier posted and it will stabilize better, just by having the cool mass in it should carry it through the 90 to 100 degree daytime temps. Earlier the bus interior was 104 with outside in the lower 90s. That might be asking too much for a cool down when empty. I remember being in Las Vagas in the scorching heat and the fridge temps rose then also. That was the trip that I found out that on a three way fridge the 12v portion is worthless. i haven't been in one spot long enough to see if 120v will work. Is it worth switching if AC is available?
L. Christley - W3EYE Amateur Extra
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Offline JohnEd

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Re: Absorption refrigerators - a real pain!
« Reply #9 on: July 04, 2011, 08:42:06 PM »
Barn Owl,

The burner is a remarkably small affair.  Mine was the size of a nickel laying flat.  The flame was 3/16 inch high and even across the burner.  Mine once had a piece of rust drop and that interrupted the flame on half the burner and my refer got anemic.  The fix is to just hit it with and air hose nozzle to blow out the little holes in the burner face.

I banged on the side of my burner "flu".  That caused a lot of rust and crap to fall out and block the burner.  That was step one.  Then I blew out the burner.

After lighting mine I waited 15 minutes and the floor of the freezer was solid frost.  Running correctly, the things are magic.  I then ran my arm up into the rear chamber of the refer space and felt the chimney/flu.  It was pistol hot at the top and that proved to me that it was clear.  The burner I could see was good as it had that pale blue flame across its top.

I could look up the refer space to the large vent in the roof.  That is critical as if it is plugged the space behind the refer will accumulate heat and eventually stop the refer from functioning at full capacity.  There are cobwebs formed by tiny critters that are transparent but I swear those webs must be hermetical barrier cause no air goes thru them at all.  My vent had no screen and I could run my fingers under it and determine that there were no webs in it.  If it had a screen I would have torn it out.

A tech told me that there didn't seem to be any middle ground with an absorption unit....they either worked fine or quit completely.  To me that makes no sense as they have a temp control and thermostat so why couldn't that fail and give you "half" the cooling?  Dunno, but the tech said!  The electric heater is intended to keep the refer chilled while you fetch a full gas bottle.  The tech said they would not chill or freeze if started on AC and barely limped into cool territory.  Hope the discussion helps.  I only remember this wisdom that others shared and didn't pioneer any of it, such as it is.

Good luck and I am really interested in what you find and how the refer works after service.  Disappoints me that so many switch over to electric powered compressor types that add so much complexity to boon docking with bat charging and such.  My RV is so trouble free in that regard.
If I was stymied with a refer problem I would spend the money to have mine looked at by a fact auth service tech before I made a serious move.

John

PS:  Clifford knows of a shop that will sell you a rebuilt cooling unit for the lowest price I ever heard of.  Maybe he will post the links in this thread, again.......

"An uneducated vote is a treasonous act more damaging than any treachery of the battlefield.
The price of apathy towards public affairs is to be ruled by evil men." Plato
“We can easily forgive a child who is afraid of the dark; the real tragedy of life is when men are afraid of the light.”
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Offline Barn Owl

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Re: Absorption refrigerators - a real pain!
« Reply #10 on: July 04, 2011, 09:00:47 PM »
I will admit to having a thing for these fridges. They are like magic, getting cold from a flame is really something. I also forgot to mention that I dug up a set of D batteries and got the circulating fan running that the PO had bought. What the heck, some people swear by them. I am almost 100% certain that I don't have any leaks and everything on the back side is nice and toasty. The flame is very uniform and is sucked rite up the flue. That would leave a possible partial boiler blockage if there was a fault. It would have had to happen under the PO's watch, because I am ultra careful not to operated it out of level and not moving. I am starting to think I need to give it a chance and a few days. Most likely everything is working and my paranoia is over working. We will see.
L. Christley - W3EYE Amateur Extra
Blue Ridge Mountains, S.W. Virginia
It’s the education gained, and the ability to apply, and share, what we learn.
Have fun, be great, that way you have Great Fun!

artvonne

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Re: Absorption refrigerators - a real pain!
« Reply #11 on: July 04, 2011, 09:06:25 PM »
  The basic design dates back about 100 years. Built properly they work amazingly well and are extremely efficient. Built with quality using high grade materials, they could work forever. There are Servell Refrigerators from the 30's and 40's that are still working, consuming no more power than a light bulb. Dometic RV refrigerators from the 60's are still around and working well, so what happened?

  They went cheap, because they, and Norcold, have no real competition and they can get away with it. Simply because the majority of new RV buyers trade them off after a year or so, its the second or third owners seeing the problems.

  Anything after the 1980 are junk, and some earlier. The boiler and all the tubing used to made of stainless or high grade steel, stuff that wouldnt corrode inside reacting to the chemicals that make it work.

  The crappy metals they use corrode and plug up the passageways. Or they rot out and lose Ammonia. If its just plugged and not cooling well, some said dumping them upside down for a day or two might spark them back to life. Otherwise you either have to have a guy fix it, or buy another one.

  I will not have another one, ill have a compressor type.

  

Offline JohnEd

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Re: Absorption refrigerators - a real pain!
« Reply #12 on: July 04, 2011, 09:21:08 PM »
Art,

That is news to me and I don't like it one bit.  If I thought this thing was only going to last a few years due to planned obsolescence I would be into a DC compressor model really quick.  Sad story, but thanks.  Time will tell, for my action, anyway.

The one I had that lasted forever and was still working when I gave it to the RV repair shop was made in 73.  The metal floor of the freezer compartment got so cold in 15 minutes that your skin would stick to it.  That thing never ceased to amaze me.  The innards of one of these is so bone simple that you should have not a single problem remaning the thing out of stainless.  Finding someone to charge it will present somewhat of a bigger challenge.

John
"An uneducated vote is a treasonous act more damaging than any treachery of the battlefield.
The price of apathy towards public affairs is to be ruled by evil men." Plato
“We can easily forgive a child who is afraid of the dark; the real tragedy of life is when men are afraid of the light.”
—Pla

artvonne

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Re: Absorption refrigerators - a real pain!
« Reply #13 on: July 04, 2011, 09:46:30 PM »
  Theres guys around here and there that fix them. Ask them, theyll tell ya. That old addage that they dont make em like they used to applies to everything. Just be nice if once in a while someone out did themselves.

 

Offline pvcces

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Re: Absorption refrigerators - a real pain!
« Reply #14 on: July 04, 2011, 10:38:57 PM »
HI, JohnEd. The reason that these things rust so bad is that the ammonia requires steel, not stainless, or so I have been informed. Our Dometic from the mid nineties would drop so much rust every time that we let it set a couple of months that it would completely block the burner.

On the other hand, the Norcold that we replaced it with, built somewhere around 2000, had at least twice the insulation and we have only had just a bit of rust fall down onto the burner. It cools promptly and has worked fine, even when in 110 degree weather. It doesn't have a flue booster fan, either. And the 12 volt part works, but the manual is clear; it is only to be used to keep an already cold refrigerator cold, say in tunnels or any place that requires the propane to be off.

For what it's worth.

Tom Caffrey
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