12V compressor vs. 3-way absorption fridge - Fiberglass RV
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Old 03-17-2022, 10:21 AM   #1
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Name: Clayton
Trailer: 1979 Trillium 4500
Manitoba
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Question 12V compressor vs. 3-way absorption fridge

I am at a crossroads. I have a 1979 Trillium 4500 that has an empty space where the 3-way fridge used to be. (30"H X 20-3/8"W X 20-1/2"D)

Decision: 12V compressor fridge vs. 3-way absorption fridge?

I have no battery or solar panels as of yet so I would have to at least buy a battery regardless of the decision.

I have a gravity furnace and a stove top that use propane. Propane pipe to fridge cavity already exists.

Existing electrical need is for interior and porch lights (LEDs), plus whatever devices I might want to charge. I also have a number of Ryobi 18V batteries with a lantern, USB charging, and fan we would often bring along when tent camping in the past.

Do I get a 3-way fridge and smaller battery or a 12V with increased battery/solar/tiny generator.

Other factors:

We would not boon-dock for more than 3-nights at a time between towing very often if at all, for electrical need calculations.

Least amount of hassle AFTER initial installation is important but not imperative. More hassle during initial installation is ok if it leads to less daily hassle.
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Old 03-17-2022, 11:23 AM   #2
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I went with a 2-way fridge ( propane and 120VAC ) because 12VDC is so inefficient. When purchasing my trailer I discussed this with Reace (Escape Trailer Industries owner at the time ). He pointed out that if you camped a few days and depleted your battery by running fan, furnace, lights, when you moved to a new camp you would arrive with a depleted battery, even with charge from the tow vehicle, because the vehicle would not provide enough charge for both the trailer battery and fridge ( running on DC ).
As for a generator, more and more campgrounds limit their use to a few hours a day. I use a couple 40 watt solar panels and leave the generator ( and gas can ) at home.


A 12VDC compressor fridge is going to require thousands of dollars in batteries and solar panels to work at all.
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Old 03-17-2022, 11:34 AM   #3
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Quote:
Originally Posted by Glenn Baglo View Post
I went with a 2-way fridge ( propane and 120VAC ) because 12VDC is so inefficient...

Did you find that the fridge would remain cold enough if you drove for 8 hours with it running on nothing during that time?
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Old 03-17-2022, 11:51 AM   #4
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Did you find that the fridge would remain cold enough if you drove for 8 hours with it running on nothing during that time?
I run the fridge on propane on the road, except for tunnels, ferries and refuelling. I drove 4-5 hours once with ice cream in the freezer and fridge off, no opening the door. When I got home, I had ice cream that was easy to scoop, but still ice cream. Of course, it was early October.
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Old 03-17-2022, 11:53 AM   #5
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Yah, it's a tough decision. I'm also debating propane vs. solar. On one hand, solar could supply your refrigeration needs indefinitely, but on the other hand propane can power your fridge for quite some time, especially since I plan to carry 87 lbs., (2 x 43.5 lbs. forklift propane tanks). The 12DC compressor fridges seem less problematic. I have no real-world experience so please feel free to correct me, but they appear to be less sensitive to high ambient temperature. Basically, they cool better. However more effort would be necessary to keep your solar cells pointing at the sun. This could involve moving around solar cells that are not mounted to your trailer, and vulnerable to theft. Also, it would probably be a good idea to upgrade to lithium batteries.

The absorption fridge would just keep burning propane, till it runs out. But in this day and age, burning hydrocarbons is not politically correct. There are methods of dealing with the high ambient temperature limitation. The fact that you are a Ryobi guy, as am I, gives you the option of precooling the air at your fridge vent, with this:

Name:   Bucket Fan.JPG
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Like I said tough decision.
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Old 03-17-2022, 12:02 PM   #6
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I was just going through the manual for a Norcold 305 2-way and it says it can be run on propane while travelling which previous to Glen's post I thought was a no-no, but there it is... his real life example, plus a statement in the manual so that is no longer a factor against propane method.
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Old 03-17-2022, 12:03 PM   #7
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Yah, it's a tough decision. I'm also debating propane vs. solar. On one hand, solar could supply your refrigeration needs indefinitely, but on the other hand propane can power your fridge for quite some time, especially since I plant to carry 87 lbs., (2 x 43.5 lbs. forklift propane tanks). The 12DC compressor fridges seem less problematic. I have no real-world experience so please feel free to correct me, but they appear to be less sensitive to high ambient temperature. Basically, they cool better. However more effort would be necessary to keep your solar cells pointing at the sun. This could involve moving around solar cells that are not mounted to your trailer, and vulnerable to theft. Also, it would probably be a good idea to upgrade to lithium batteries.

The absorption fridge would just keep burning propane, till it runs out. But in this day and age, burning hydrocarbons is not politically correct. There are methods of dealing with the high ambient temperature limitation. The fact that you are a Ryobi guy, as am I, gives you the option of precooling the air at your fridge vent, with this:
Attachment 145233

Like I said tough decision.

I have that exact fan already!
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Old 03-17-2022, 12:14 PM   #8
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plus a statement in the manual so that is no longer a factor against propane method.
It never was a factor. No laws prohibiting running on propane, except for ferries, some tunnels and while refuelling.
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Old 03-17-2022, 12:40 PM   #9
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12 volt Danfoss compressor

Quote:
Originally Posted by Glenn Baglo View Post
A 12VDC compressor fridge is going to require thousands of dollars in batteries and solar panels to work at all.
Because absorption refrigerators are not allowed in a semi, 12-volt compressor refrigerators are used.
The Danfoss compressor is the most efficient out there. They do not require thousands of $ in batteries unless that’s your choice. (I just run on gas when on the highway. But if your refrigerator is in the street side the flame often blows out when you meet a truck.)
https://www.truckcamperadventure.com...nd-a-few-tips/
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Old 03-17-2022, 12:45 PM   #10
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Originally Posted by AC0GV View Post
Because absorption refrigerators are not allowed in a semi, 12-volt compressor refrigerators are used.
The Danfoss compressor is the most efficient out there. They do not require thousands of $ in batteries unless that’s your choice. (I just run on gas when on the highway. But if your refrigerator is in the street side the flame often blows out when you meet a truck.)
https://www.truckcamperadventure.com...nd-a-few-tips/
Run on gas?
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Old 03-17-2022, 12:53 PM   #11
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My 3 way blows out if I try gas while driving. 12 volt can't meet demand with the wiring I have. I run the fridge on 110 from an inverter in the car while driving. Works for me.
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Old 03-17-2022, 01:44 PM   #12
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What are you asking?

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Run on gas?
Yes I run my stock Scamp unit on gas. The compressor unit runs on electricity only. I have no reason to change until the stock unit fails and the last time I had one fail I did not know about the compressor units.
Not sure why the link opens to the bottom of the page on my computer.


https://www.dometic.com/en-nz/outdoo...specifications
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Old 03-17-2022, 02:05 PM   #13
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Ah, now I understand. I didn't realize that you were talking about two different fridges.
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Old 03-17-2022, 02:23 PM   #14
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Originally Posted by Lynn Eberhardt View Post
My 3 way blows out if I try gas while driving. 12 volt can't meet demand with the wiring I have. I run the fridge on 110 from an inverter in the car while driving. Works for me.

I am confused. Is the fridge portable and moved to inside your car running off of an inverter or is the inverter in the car and you are somehow getting 110 to the fridge in the trailer (while at the same time unable to get sufficient 12V there)?
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Old 03-17-2022, 02:52 PM   #15
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I guess my flame doesn't blow out because the fridge is on the passenger side.
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Old 03-17-2022, 03:36 PM   #16
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We would not boon-dock for more than 3-nights at a time between towing very often if at all, for electrical need calculations.
I have been at a campground without electricity and have run my 12 volt portable compressor fridge (7.7 amp draw when running) for 3 days using my 100 amp hour AGM true deep cycle battery and 2 solar panels in mostly shade (wooded campsite) without running the battery below 50% capacity. Now I don't run a furnace and I limit my other battery use in that situation. If my panels have access to sun, I can have the battery charged in just a couple of hours when the sun comes up. There are built in compressor fridges that use as little as 2.2 amps when running which is a third of what I use now. I paid $179 for the battery, $30 for the solar controller and about $220 for the solar panels. Definitely not thousands of dollars. In addition, you can get a decent Lithium Iron Phosphate 100 amp hour battery for around $350 to $400 these days. That would definitely power the fridge for 3 days plus any led lights and usb chargers. The 12 volt compressor fridges are comparable in price to a 2 way or 3 way fridge depending upon the brand you buy.
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Old 03-17-2022, 03:39 PM   #17
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The small fridge in our Scamp uses a little more than 120 watts to stay cold. That's 10 amps at 12 volts. The 7 pin connector and the trailer wires to which it connects can't deliver that amount of current all the way back to the fridge. That same 120 watts is only 1 amp at 120 volts. I use short, heavy wires from my car's 12 volt battery, which is in the rear, to an inverter which changes that 12 volts/10 amps to 120 volts/1 amp. (Yes, I know about losses - I'm rounding.) I run that 120 volts out through the tailgate with a standard flat extension cord to a connection with the 120 volt system in the trailer. The utility company uses the same idea to deliver power long distances to customers on the grid.
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Old 03-17-2022, 04:02 PM   #18
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That's 10 amps at 12 volts. The 7 pin connector and the trailer wires to which it connects can't deliver that amount of current all the way back to the fridge.
You need to have the wire from the battery/alternator to the 7 pin connector rewired or check your connections for corrosion. The 12 volt power port in the passenger compartment is rated for 15 amps on most vehicles. According to a wire gauge chart, 14 gauge wire should handle 10 amps to a run length of 10 to 13 feet. 12 gauge wire would definitely be adequate to carry the current.
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Old 03-17-2022, 04:13 PM   #19
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I have been at a campground without electricity and have run my 12 volt portable compressor fridge (7.7 amp draw when running) for 3 days using my 100 amp hour AGM true deep cycle battery and 2 solar panels in mostly shade (wooded campsite) without running the battery below 50% capacity. .
What size is this fridge? What do you keep in it and how often do you open it?
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Old 03-17-2022, 04:36 PM   #20
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I have been at a campground without electricity and have run my 12 volt portable compressor fridge (7.7 amp draw when running) for 3 days using my 100 amp hour AGM true deep cycle battery and 2 solar panels in mostly shade (wooded campsite) without running the battery below 50% capacity. Now I don't run a furnace and I limit my other battery use in that situation. If my panels have access to sun, I can have the battery charged in just a couple of hours when the sun comes up. There are built in compressor fridges that use as little as 2.2 amps when running which is a third of what I use now. I paid $179 for the battery, $30 for the solar controller and about $220 for the solar panels. Definitely not thousands of dollars. In addition, you can get a decent Lithium Iron Phosphate 100 amp hour battery for around $350 to $400 these days. That would definitely power the fridge for 3 days plus any led lights and usb chargers. The 12 volt compressor fridges are comparable in price to a 2 way or 3 way fridge depending upon the brand you buy.

What are the rated wattage of your 2 solar panels?
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