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Old 06-18-2020, 09:13 AM   #1
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Altitude or attitude?

I live here at an altitude of 6700 feet. Well today there seems to be only two conclusions to be drawn. As a 3-way, the Dometic RM8551 fridge in my trailer is a lemon, or, the fridge is adversely affected by altitude. Or both.

It does work great on shore power and on battery power. On propane? Not!

Yesterday I disassembled the burner lines and gave everything yet another thorough cleaning. The 1/8th tubing, the orifice, even the electrodes creating a spark, everything connected to producing a healthy, robust pilot light, all once again cleaned and blown out as best as humanly possible.

Then I turned the fridge on to propane, 5 full dots. When I did that, at 3:40 PM it was 87°F in the trailer and 68° in the fridge. At 6:10 PM last night I have a very, very robust pilot light and the chimney is quite hot. (So yes, the regulator pressure is just fine.) But, it was 90° in the trailer, 73° inside the fridge.

This morning at 7:24 AM, after all night on 5 dots propane, it is 64°F in the trailer, and --- 55°F in the fridge! Terrible.

How can I have such a robust pilot light but no commensurate propane cooling? See that towel over there? Just threw it in. To paraphrase an old Frank song… My story is much too sad to be told, but everything seems impossibly un- cold.

This is all insanity. When looking for a replacement fridge for your rv before paying the big bucks you need to know the following criteria.

First, will it fit through the door of the trailer?
  • Is it the right size for your cabinet area?
  • Will it work in hot weather?
  • Will it work at the altitude you will be camping at?

Does Dometic tell you that? Not that I can find. I heard they make a fridge specifically for tropical zones (Australia?) but apparently they are keeping that a secret here in the US. Zero reference if they also make a fridge for higher elevations. The Dometic website is such a jumble, so slick, but absurdly inept for the real world.

Note I did include the word “attitude” starting this topic.
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Old 06-18-2020, 09:26 AM   #2
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I have the same problem, at sea level.
Works on shore power but not propane although the propane seems to be heating correctly.
But I haven't torn mine apart yet.
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Old 06-18-2020, 09:34 AM   #3
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There have been a few owners who found that the way the factory installed the fridge was causing problems with cooling. I believe they changed the baffling in the cabinet so the movement of air across the back of the fridge was enhanced. You can try searching for the threads or maybe one of them will pipe up. I don't have a propane fridge. The newer 12 volt compressor fridges work really well. I'm using a portable Dometic currently but plan on installing one permanently in my boler.
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Old 06-18-2020, 09:54 AM   #4
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Been there done that, Alex. A waste of time.

Thinking, wouldn't it be swell if some suit working at Dometic reads this post and makes the effort to address my issues? They don't take phone calls and they ignore emails, soooo....??
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Old 06-19-2020, 01:41 PM   #5
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Absorption Fridges

The absorption type fridges can cool only so many degrees below the ambient temperature. So the hotter it is outside, the warmer it will be inside the box.
The rear of the fridge needs to have plenty of outside air circulation over the condenser coils to dissipate the heat extracted from the food inside.
you can see, that "cooling" the condenser with "hot" air is a no win situation.
Some of us bring a plastic bottle(s) of frozen water inside the box to help keep it cold.
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Old 06-19-2020, 02:52 PM   #6
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Most of what was said needs to be listened to. Now violated expectations seems to the rule when it comes to refrigeration. These things don't cool the same way your home fridge does. The easiest thing to do is get over it and don't carry sensitive foods. Learn from backpacking books how to carry non refrigerated foods,
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Old 06-19-2020, 04:40 PM   #7
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e. The newer 12 volt compressor fridges work really well. I'm using a portable Dometic currently but plan on installing one permanently in my boler.

I'm not familiar with 12v compressor refers for RVs, but 35 years ago I installed one (an icebox conversion kit) in a 30' sail boat. It came in two pieces, the compressor/condenser unit and the evaporator (freezing) unit that went in the built in icebox, with necessary pre-charged connecting lines. Now you might know that sail boats don't have great battery charging power. Anyway, it worked perfectly with little power drain. As I remember the compressor/condenser unit was rather bulky. I know this doesn't answer the original problem, but if I had problems with my current 3-way I would certainly look into RV compressor refers.
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Old 06-19-2020, 04:58 PM   #8
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https://www.truckfridge.com/portable...ator-freezers/

I have the TB31A but with a different manufacturer label.. same fridge. AC or DC. Quite efficient and with a good solar battery setup it can replace an absorption fridge for boondocking (except its smaller). There are larger built-in models with the same compressor technology and I think they use nearly the same amount of power.

BTW, a few possibilities.. the chimney is clogged so it gets hot but the heat does not rise that well. Trailer not level. Fridge not insulated. Fridge not installed right (airflow lacking).

Where did you measure the temp? On the cooling fins?
Is 5 half way? Try turning it on max cool setting?
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Old 06-19-2020, 05:46 PM   #9
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Mount a couple of computer fans to cool the fins in back of the refer. There are kits made for this that run on 12 volts.
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Old 06-19-2020, 07:55 PM   #10
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I am still hoping some genius physics expert reads my initial post and after that understands the issue at hand and will offer useful advice. A real solution.

The prime question I guess, really is... why does altitude, it does seem to be altitude, that adversely affects performance? The magic number seems to be 5500 feet. Yes, my robust pilot light, as I have shown, seems to not produce the heat that produces coldness. But it just ain't going to burn any bigger or hotter. How about cutting open the cooler tubes and replacing the liquid inside with something that does a better job?

My fridge is well insulated, well ventilated (yes, got the two Texas fans in back), and though 6700 feet altitude is not down in the swamp it certainly is not up in the Rocky mountains. I do breathe quite effortlessly on the oxygen we got here so the thinking is if I can do it, so should my fridge.
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Old 06-19-2020, 08:31 PM   #11
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Could it possibly be the propane regulators? A propane dealer may be able to run a pressure check and see if it is adequate for your altitude.
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Old 06-20-2020, 01:28 AM   #12
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Originally Posted by MyronL View Post

The prime question I guess, really is... why does altitude, it does seem to be altitude, that adversely affects performance? The magic number seems to be 5500 feet. Yes, my robust pilot light, as I have shown, seems to not produce the heat that produces coldness.....



Does it work well, on propane, at Sea level?
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Old 06-20-2020, 06:01 AM   #13
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Mount a couple of computer fans to cool the fins in back of the refer. There are kits made for this that run on 12 volts.
https://i5.walmartimages.com/asr/fab...2&odnBg=ffffff

We were in Texas for a week of 90+ degree weather in early June. Knowing what I was in for with the the refrigerator I picked up this USB fan at Walmart. Using a 10k mAH battery pack for power I gave it an overnight and all day trial by placing it in the cabinet blowing up the vent, across the coils.
We stayed at 40 degrees +/_ 2 degrees the whole trip, which I count as a win.
For the few times a year I need it I may just stick with this temporary set up.
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Old 06-20-2020, 08:47 AM   #14
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RE: post #1, paragraph 2, and all of post #10. (Waaaa)
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Old 06-20-2020, 09:47 AM   #15
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RE: post #1, paragraph 2, and all of post #10. (Waaaa)
I deleted my post. While I'm not convinced the referenced sections address all my questions, I realized I had misinterpreted the intent of this thread. Should have paid more attention to the last paragraph of post #1!

You have piqued my curiosity, though. I'm going to test the performance of my own fridge on LP and 110V at 5500' and 7000'. No plans to head to sea level anytime soon, although in a normal year, that's exactly where we'd be right about now. Instead we're parked at home headed into our second heat wave of the season and breathing smoke from several regional fires.
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Old 06-20-2020, 10:50 AM   #16
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Roger that, Jon. No worries... this issue is a pretty old one. I am just hoping this thread piques the interest of any of the geniuses out there on line, gets them to read carefully, motivates and ponder a true remedy. Hey, geniuses, consider this a homework assignment. All others need not respond.

Got friends around Tucson... saw the news pix. You have my sympathy.
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Old 06-20-2020, 11:18 AM   #17
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Myron,

I have a friend with a Dometic fridge in their new trailer that would not cool, no matter how long it was left burning. An RV repair shop gave up on it and said it was "defective".

I found out the trailer had been parked on a severe angle at the dealer, with the system running, and after that it would not work. A popular, old fashioned fix for absorption fridges is to turn them upside down for a while, after they have been out of level enough to make them stop cooling. They have to be fairly level, or used while driving.

I suggested something to try before giving up completely, or pulling it out to turn it upside down.

I asked them to start it and leave it running for a while, maybe several hours to get the hot part fully warmed up, and the absorption hot enough to work. And then take it for a drive. During the drive I asked them to be sure and go around lots of corners and over some bumps.

They did this and it fixed it. It is now working normally.

In reading your story, you repeatedly commented how big the flame was. "Robust, turned up to 5 dots, ain't gonna burn any bigger".

I wonder if the flame is too big? The flame doesn't burn bigger to make more cold, it burns longer. Older ones would turn way down when the box was cold and up to make more cold, but that was just so they could stay lit as a pilot light. Small in that case, was a pilot light, big was the working flame. Newer ones go out and then re-light when more cold is needed. But they don't just turn up to a bigger flame to make more cold. Bigger is not necessarily better. Bigger doesn't necessarily equal more cold.

Someone mentioned that they can only go a certain amount colder than ambient, and that might be the problem in your case. It is not the problem. Absorption systems do have their limits, but mine, for instance was 6 degrees F in the freezer compartment today while outside temp was 90. And yours works on 120 volts. So you are not out of its working range.

So, you might have the dreaded bubble problem, that can be solved by driving it around while it is trying to cool. Or you might have too large of a fire that is overwhelming it. The latter is just a theory and I have never seen that happen, but you repeatedly commented how big the fire is. Turn it down. Or restrict it somehow and see if that helps. It is not about giving it more and more fire to get cooler and cooler. All it has to do is boil the ammonia to separate it from the water, and cause hydrogen bubbles to form. The boiling point in the system is probably a little over 100* F.

While it is on, the heat should be getting all through the finned tubing on the rear of it. Compare the temp of the tubing when running on 120 volts, with the temp while running on propane. This will prove that the flame heat is getting into the system and it will show you how much heat is needed to cool the box on 120 volts. Way more heat there from the flame might be the problem.
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Old 06-20-2020, 11:36 AM   #18
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... All others need not respond.
...
I'm sorry I did, even though my suggestion is a valid one to consider. That is all I will say about this approach you are taking to getting advice.
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Old 06-20-2020, 12:12 PM   #19
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RE: post #1, paragraph 2, and all of post #10. (Waaaa)
Please answer post #12.
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Old 06-20-2020, 02:37 PM   #20
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Thanks for asking.

Fridge on battery, towing to Albuquerque. Plan was to get to a big parking lot in ABQ then switch from battery power to propane and wait, to see what happens with the fridge cooling on propane at the lower altitude.

Time --Fridge temp --Trailer temp --observation
10:40 am 64° 71° At home, 6700 ft elevation - Turn fridge on battery power 5 dots
11:13 am 63 73 - -Arrive Home Depot, ABQ, Switched fridge to propane 5 dots
11:26 am 62 - --Home Depot parking lot - 5,474 ft elevation
12 noon 58 79 ---Looking good.
1 PM 57 83 - -- Drive to Cabellas, elevation 5,148 ft, It's dropping, still on propane 5 dots.
2:40 pm 64 89 - -Arrive now back home, and still on propane.
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