WOW! Absorption fridge vs compressor fridge

[GSXR1000]

I did a 24 hour test of my 2 fridges in my toy hauler. this is measured at the 12v battery using a 1000w inverter no other DC loads.

Absorption fridge - 514ah (6737wh)
compressor fridge - 74ah (984wh)

people have said absorption is more efficient... no way.. maybe in the 70s when natural gas was so cheap..
I do realize the compressor fridge is 60% so add 30% more energy still way less

 

[snoobler]

I did a 24 hour test of my 2 fridges in my toy hauler. this is measured at the 12v battery using a 1000w inverter no other DC loads.

Absorption fridge - 514ah (6737wh)
compressor fridge - 74ah (984wh)

people have said absorption is more efficient... no way.. maybe in the 70s when natural gas was so cheap..
I do realize the compressor fridge is 60% so add 30% more energy still way less

No sane person with a basic understanding of the issue has ever said that. Moving heat is about 5-6X more efficient than making heat.

Pity me. I have one of the double wide units with a 400W element that runs about 16 hours per day on setting 1 out of 9. It will run almost constantly on 5 and above. When we're offsite, I only power it during solar hours (keeps it cool enough to keep the mold at bay). When we're on site, I switch to auto and use LP at night.

 

[GSXR1000]

No sane person with a basic understanding of the issue has ever said that. Moving heat is about 5-6X more efficient than making heat.

Pity me. I have one of the double wide units with a 400W element that runs about 16 hours per day on setting 1 out of 9. It will run almost constantly on 5 and above. When we're offsite, I only power it during solar hours (keeps it cool enough to keep the mold at bay). When we're on site, I switch to auto and use LP at night.

absorption fridge still "pumps" heat out with an ammonia/hydrogen based refrigerant... but yes the use of heat to move refrigerant sucks lol

 

[Freqz]

Yes, they’re shockingly inefficient— it’s essentially running a resistive heat element on electric only mode.

If propane is easier to get than electricity they make sense but only then.

 

[GSXR1000]

Yes, they’re shockingly inefficient— it’s essentially running a resistive heat element.

If propane is easier to get than electricity they make sense but only then.

even 5 years ago before affordable lithium batteries and cheap solar.. propane was the way to go.

 

[LB3]

We ditched our propane fridge 5 years ago for a 12v marine fridge. We went from being propane limited to being black tank limited with only a modest decrease in our solar overhead. Even at 46 degrees latitude we we can still go a full month without shore power, gen, or alternator.

 

[Freqz]

even 5 years ago before affordable lithium batteries and cheap solar.. propane was the way to go.

Yep, but electricity (solar) is *much* easier now. Even putting 500 amp hours into your electrical system with a generator would be problematic (or obnoxious, at least)without high C rate lithium. 900Whr is less than 1/2 an hour with my charger or a little over an hour of solar in my current rig.

 

[willo]

Commercial, large scale can be more efficient - but yeah I find myself seriously considering converting my year old dometic to a compressor.

 

[GSXR1000]

Commercial, large scale can be more efficient - but yeah I find myself seriously considering converting my year old dometic to a compressor.

what size dometic?

 

[willo]

what size dometic?

Double door RM1350. What's really ironic here is that I also have a compressor based CFX95 cooler that's fantastic. The absorption fridge is actually far more expensive from the factory. Anyhow, it appears that I can get a kit to convert it from JC refrigeration.
I'm really liking the idea of reducing my propane usage and honestly the absorption based units are kind of lame.
The freezer in my camper? Good luck putting ice cream in there. (In my compressor cooler? No problem)

Honestly if they just worked better, I'd be down with it but the performance difference makes it attractive to me.

 

[snoobler]

FWIW, the freezer on our double door Norcold is brutal. Even on setting 1, it's 0-10°F. I have mixed feelings about the JC option. I'd rather unload my whole unit for a small sum and then replace it with an actual residential unit. One can usually find one that fits if you can live with it sticking out an inch or two.

 

[willo]

Nice to know on the Norcold. I'm jealous! I looked up my fridge, it runs from 3-5k - absolutely nuts. I suppose I could add some fans to improve the heat exchanger performance but really. It's basically a brand new unit.
One thing that's very attractive for the JC vs a residential... They offer a 12v DC version.

Oh, I did find that I could freeze ice in the dometic, but the insulation properties are wack. (I wouldn't mind getting my hands on the product line manager to discuss their short comings) There are major hot/cold differentials in the freezer. I suppose I'll have to break out my Flir again.

I'm thinking of running some fridge load testing this week. I figure it's going to eat around 400 watts but I'm not sure how linear that load is.
When I'm down I'm going to toss a few gallons of water into the fridge and freezer and run the inverter.

400w x 24h = 9.6Kwh per day which is nuts but it should settle into a better duty cycle after cool down.
I'll be running the near worst case scenario this round - room temperature water will take some energy for sure.
Outside temp is still pretty mild...
(I've got my 14kwh pack now, and I've observed 5kwh+ solar days recently so I think I'll be ok budget wise)

Now the question is if I'm motivated enough to put together a temperature data logger before I do this.
Oooh, yeah I have an old pi here, wireless, a few sensors and a breadboarding breakout for it...

 

[Rider]

I've posted this before.... I have a 3.5 cf compressor freezer with an external thermostat so I can regulate to fridge temps. Average usage is 10w per hour averaged over a few days. I ran it for 36 hours before the 45aH SLA battery dropped below 12VDC with no external charging. If connected to the solar panel, it will run indefinitely, even in the winter.

 

[willo]

Compressor is the way to go, in my case I want to justify dropping 1k on a conversion.

 

[GSXR1000]

Nice to know on the Norcold. I'm jealous! I looked up my fridge, it runs from 3-5k - absolutely nuts. I suppose I could add some fans to improve the heat exchanger performance but really. It's basically a brand new unit.
One thing that's very attractive for the JC vs a residential... They offer a 12v DC version.

Oh, I did find that I could freeze ice in the dometic, but the insulation properties are wack. (I wouldn't mind getting my hands on the product line manager to discuss their short comings) There are major hot/cold differentials in the freezer. I suppose I'll have to break out my Flir again.

I'm thinking of running some fridge load testing this week. I figure it's going to eat around 400 watts but I'm not sure how linear that load is.
When I'm down I'm going to toss a few gallons of water into the fridge and freezer and run the inverter.

400w x 24h = 9.6Kwh per day which is nuts but it should settle into a better duty cycle after cool down.
I'll be running the near worst case scenario this round - room temperature water will take some energy for sure.
Outside temp is still pretty mild...
(I've got my 14kwh pack now, and I've observed 5kwh+ solar days recently so I think I'll be ok budget wise)

Now the question is if I'm motivated enough to put together a temperature data logger before I do this.
Oooh, yeah I have an old pi here, wireless, a few sensors and a breadboarding breakout for it...

Jealous??? my norcold 8cuf used 6.7Kwh in 24 hours...

 

[willo]

@GSXR1000 Before I forget, did you have mass in there? It makes a big difference. (You need something in there to stabilize the temperature or you're just fighting the outside/insulation.

 

[GSXR1000]

both empty

 

[willo]

both empty

Yeah, you may want to re-test with some mass. I found that my dometic compressor cooler was using a ton of power until I added stuff inside. It made a significant dent in the energy required. (This is why I mentioned adding water to mine for testing)

 

[Rider]

(This is why I mentioned adding water to mine for testing)

I did the same. 5 or 6 half-gallon milk containers filled with water.

 

[JeepDaddy]

Absorption refrigeration is designed for use with propane off-grid, typically in RVs. They typically have a 120VAC electrical heating element for use when shore power is available and sometimes a 12VDC element while driving. The fridges do not use much propane at all. Propane is cheap, easy and available for most people.