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Old 06-19-2019, 05:25 AM   #1
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Default Odd inverter question

Ok. This may (probably?) be a stupid question but....I have a Dometic 3-way fridge which works ok but is wimpy in 12v mode. Only use it when driving but it still doesn't cool as efficiently as when it's on LP or 120v. Could you use an inverter and it on 120v. when driving? Would the inverter be sustained by the alternator/battery when driving so that driving would compensate for its use? Not making my question very clear, eh?

Of course, the next question is would running it off an inverter really equate to 120v shore power? Or would there be no gain? On my fridge there are separate 12v and 120v elements.

A humorous aside. Getting ready for trip. Had fridge on 120v and lowest thermostat setting. Got fridge down to 38 overnight. Sat in sun during day with windows closed (neighbors had gravel dumped raising huge dust cloud). Temp in RV got to 117 (we're talking PX,AZ). Fridge jumped to 58.
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Old 06-19-2019, 10:28 AM   #2
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Yes, you can run the fridge off the inverter while driving & yes it should perform a bit better than on 12V as it does equal shore power. I do that in both of my RV's.
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Old 06-19-2019, 10:48 AM   #3
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Originally Posted by GallenH View Post

A humorous aside. Getting ready for trip. Had fridge on 120v and lowest thermostat setting. Got fridge down to 38 overnight. Sat in sun during day with windows closed (neighbors had gravel dumped raising huge dust cloud). Temp in RV got to 117 (we're talking PX,AZ). Fridge jumped to 58.
A good fan ventilation system of the backside of the fridge should help somewhat. Park with the refrigerator on the shade side of the van. Solar heating of the fridge vent cavity can cause the fridge efficiency to drop significantly.
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Old 06-19-2019, 02:15 PM   #4
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A good fan ventilation system of the backside of the fridge should help somewhat. Park with the refrigerator on the shade side of the van. Solar heating of the fridge vent cavity can cause the fridge efficiency to drop significantly.
I can confirm solar heating of the vent cavity is a real problem. When the sun is shining on the fridge side of my van, the cavity behind the compressor fridge reaches 20 degrees hotter than the van interior. The temp difference used to be closer to 30 degrees before I added additional insulation back there because apparently Airstream did not think it was that important.
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Old 06-19-2019, 03:25 PM   #5
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Originally Posted by GallenH View Post
Ok. This may (probably?) be a stupid question but....I have a Dometic 3-way fridge which works ok but is wimpy in 12v mode. Only use it when driving but it still doesn't cool as efficiently as when it's on LP or 120v. Could you use an inverter and it on 120v. when driving? Would the inverter be sustained by the alternator/battery when driving so that driving would compensate for its use? Not making my question very clear, eh?

Of course, the next question is would running it off an inverter really equate to 120v shore power? Or would there be no gain? On my fridge there are separate 12v and 120v elements.

A humorous aside. Getting ready for trip. Had fridge on 120v and lowest thermostat setting. Got fridge down to 38 overnight. Sat in sun during day with windows closed (neighbors had gravel dumped raising huge dust cloud). Temp in RV got to 117 (we're talking PX,AZ). Fridge jumped to 58.


It appears that your refer is working, working ok? I obviously don't know the answer, but if it is yes, it is all about making heat and cooling the heat.

Yes, you can drive down the road with ac from the inverter and the batteries will still be charging. I run on ac or propane, mostly ac, but both. Both make more heat than dc, never use it.

If I recall correctly, you have a PleasureWay. At times PleasureWay used fans to provide ventilation for cooling. Do you have a fan? Is it working? With Roadtreks, something has to be done while driving to improve, no FIX the lousy ventilation. I use fans, mostly while driving.

Bud
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Old 06-19-2019, 03:42 PM   #6
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Thanks for the replies. I actually don't have an inverter so would have to figure out if it's worth adding when that's really the primary purpose. How would I size the inverter? Where would it be placed with respect to the fridge or battery?

Yes, last year I added two computer fans to promote airflow in the fridge compartment. They're mounted pointing at an angle upward to draw air through the lower vent and direct it towards the upper vent. That seemed to improve cooling. Always hard to tell precisely since each trip involves different weather/temperature conditions.

My insulation around the fridge (viewed from the back) consists of strips of fiberglass insulation; look to be 1" thick and 4" wide. Advantage perhaps to replacing with something wider? Thoughts?

best.
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Old 06-20-2019, 12:25 PM   #7
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In BWorld, we always think of running down the road on 12 volts. Think about trailers and most Class Cs: they run down the road on propane for the refrig. Yes, you gotta remember to turn off the refrig briefly when fueling.
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Old 06-20-2019, 12:28 PM   #8
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"Yes, last year I added two computer fans to promote airflow in the fridge compartment. They're mounted pointing at an angle upward to draw air through the lower vent and direct it towards the upper vent. That seemed to improve cooling. Always hard to tell precisely since each trip involves different weather/temperature conditions."

Fans are interesting and not understood sometimes. A fan will draw air from the path with least resistance which is from the sides! I can't see your fans, but it appears that they may be inside the refer compartment and not forcing air to enter from the outside. If not, there may be 'looping' of air in the compartment.

I added 2 fans to 2 of the exhaust vents of the refer compartment, pretty much worthless until I covered the other 2 vents. Then Bingo.

Bud
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Old 06-20-2019, 02:49 PM   #9
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Default Fans .. would have been a good idea.....

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"Yes, last year I added two computer fans to promote airflow in the fridge compartment. They're mounted pointing at an angle upward to draw air through the lower vent and direct it towards the upper vent. That seemed to improve cooling. Always hard to tell precisely since each trip involves different weather/temperature conditions."

Fans are interesting and not understood sometimes. A fan will draw air from the path with least resistance which is from the sides! I can't see your fans, but it appears that they may be inside the refer compartment and not forcing air to enter from the outside. If not, there may be 'looping' of air in the compartment.

I added 2 fans to 2 of the exhaust vents of the refer compartment, pretty much worthless until I covered the other 2 vents. Then Bingo.

Bud
Our unit has a 3.6 cubic foot Dometic 3 way fridge..... unfortunately ... there's no room behind the cabinet to add a cooling fan.....
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Old 06-20-2019, 02:51 PM   #10
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Default Just switch it to battery when you are getting fuel

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In BWorld, we always think of running down the road on 12 volts. Think about trailers and most Class Cs: they run down the road on propane for the refrig. Yes, you gotta remember to turn off the refrig briefly when fueling.
That's all you have to do...... once you are back on the road it's safe to go back to the propane......
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