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Old 08-21-2020, 10:22 AM   #1
The Joymobile
 
2011 22' Sport
MERIDEN , CT
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Dometic RM 8501 3 way fridge Use Question While Boondocking.

Recently acquired a 2011 22' Sport FB with a Dometic RM 8501 3 way fridge. We've been drycamping in a 10' 1966 canned ham with no fridge (Or furnace for that matter) for several years so the AS is a huge upgrade.

We're using the fridge now on shore power while staying in a Army Corps campground and while moochdocking at relative's homes. Seems to work fine.

I did run it for a short while on propane yesterday but not long enough to tell if it was performing properly. I'll experiment more with this after we return home.

In terms of expectations, propane seems to be the preferred cooling method while dry camping since at 11A per hour, the Dometic chews through most batteries quickly. (I have read about some impressive Solar/Lithium setups...but we're not there yet).

Questions:

Assuming no solar/lithium setup, seems like 12v then is only used for very short periods of time or when traveling, correct?

How long do two fully charged 20 lb LP tanks last, running the fridge and assuming no propane heater use? I'm thinking many days...

I know this is a 3 way fridge....one has to be the most efficient. I'm assuming 120v shore power is the most efficient and cools the best....however, I have no basis in fact.

Thanks, Jeff
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Old 08-21-2020, 10:38 AM   #2
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2018 25' International
Slidell , Louisiana
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for the size refrigerator I'm going to use 7.4 BTU/min for heat loss. Propane has a heating value of 21,548 BTU/lb so that would have you using about half a pound per day.
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Old 09-25-2020, 07:37 PM   #3
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As you noted, propane is the preferred heat source when boondocking, as battery power is a big energy user when used as the power source for the refrigerator absorption cycle. If plugged in, then 120V will work just as well.

With respect to propane usage, think in terms of months, not days for a two propane tank set up. I have a 2016 22FB with the same refrigerator and have used it 3-4 weeks at a time without running out a single bottle of propane. That includes a small amount of heater use, as well as normal hot water heating every day or two.

But don't get me started on the reliability and cooling capability of our specific Dometic absorption refrigerator. Ours has given me nothing but trouble, and after constant worry about the poor cooling and potential food spoilage, plus hours and hours spent testing and diagnosing, I am about to pull it out and go with a Danfoss compressor style refrigerator. Others have had much better luck, and as always, YMMV.
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Old 09-26-2020, 02:14 PM   #4
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Dometic 3 way fridge lp performance

Quote:
Originally Posted by jmickow View Post
As you noted, propane is the preferred heat source when boondocking, as battery power is a big energy user when used as the power source for the refrigerator absorption cycle. If plugged in, then 120V will work just as well.

With respect to propane usage, think in terms of months, not days for a two propane tank set up. I have a 2016 22FB with the same refrigerator and have used it 3-4 weeks at a time without running out a single bottle of propane. That includes a small amount of heater use, as well as normal hot water heating every day or two.

But don't get me started on the reliability and cooling capability of our specific Dometic absorption refrigerator. Ours has given me nothing but trouble, and after constant worry about the poor cooling and potential food spoilage, plus hours and hours spent testing and diagnosing, I am about to pull it out and go with a Danfoss compressor style refrigerator. Others have had much better luck, and as always, YMMV.
Just got back from a 3 day boondock trip, our first, using a Honda 2200 LP conversion generator for back up. We have the 2019 16' Bambi with original lead acid battery. I plugged into the generator upon first arriving at the site to charge up the battery and get the refer adequately cooled. Ran the generator for 3 hours assuming that the battery was sufficiently charged and the refer was sufficiently cooled - which it was - ice was froozen. At this time I switched the refer to gas use only and after turning the refer off and on 4 times, I THINK the refer fired up. To confirm this, I pulled the exterior vent cover off to listen if the burner was fired up and it was. We went for a two hour walk and checked on the refer upon return and the ice was melting and it felt less cool. Check in the morning and the refer was obviously not cooling and through the night could hear the lighter of the refer clicking throughout the night. Also, the water pump struggled to operate and the lights were noticeably dim. We used headlamps all evening.
In the morning, I plugged into the generator for 3 hours and switched the refer to shore power mode to get things cool again. Unplugged and turned on the water pump and it seemed to struggle to run - like it wasn't getting enough power to operate effectively. What do you all think is the issue(s)??
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Old 09-26-2020, 03:26 PM   #5
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Quote:
Originally Posted by CRRVP View Post
Just got back from a 3 day boondock trip, our first, using a Honda 2200 LP conversion generator for back up. We have the 2019 16' Bambi with original lead acid battery. I plugged into the generator upon first arriving at the site to charge up the battery and get the refer adequately cooled. Ran the generator for 3 hours assuming that the battery was sufficiently charged and the refer was sufficiently cooled - which it was - ice was froozen. At this time I switched the refer to gas use only and after turning the refer off and on 4 times, I THINK the refer fired up. To confirm this, I pulled the exterior vent cover off to listen if the burner was fired up and it was. We went for a two hour walk and checked on the refer upon return and the ice was melting and it felt less cool. Check in the morning and the refer was obviously not cooling and through the night could hear the lighter of the refer clicking throughout the night. Also, the water pump struggled to operate and the lights were noticeably dim. We used headlamps all evening.
In the morning, I plugged into the generator for 3 hours and switched the refer to shore power mode to get things cool again. Unplugged and turned on the water pump and it seemed to struggle to run - like it wasn't getting enough power to operate effectively. What do you all think is the issue(s)??
Sounds like your battery is not lasting very long. Monitoring the 12 volts would be your first step in problem determination. If you do not have a digital multi meter, get one.
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Old 09-26-2020, 09:37 PM   #6
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If you have an Airstream with the SeeLevel monitor, then you can use that as a rudimentary battery voltage monitor. You should check to see what the voltage is when fully charged after you run the refrigerator, and then keep tabs on what it says when you are having problems. I grabbed this from another post which shows how to interpret the voltage readings of the battery, whether from a voltmeter or the SeeLevel monitor:
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