Refrigerator draw on LP mode

Chum lee wrote:

BFL13 wrote:
I tried to run my absorption RV fridge on 120v this summer off inverter with 800+ watts of solar flat on the roof in good sunshine. It didn't work out. 325w on 120v was 30 some amps draw by the inverter. I only got over 30 amps from solar around lunch time. Most of the day and all night I was losing. Gottaluv propane mode for off-grid!

Yeah, yeah, all you "experts" tell me something won't work, yet, I'm still doing it. The problem must be with me.

Chum lee

Goodness! I wasn't suggesting that at all. Sorry it seemed like it.

Wasn't trying to say it could not be done, just that it didn't work in our case.

BFL13 wrote:
I tried to run my absorption RV fridge on 120v this summer off inverter with 800+ watts of solar flat on the roof in good sunshine. It didn't work out. 325w on 120v was 30 some amps draw by the inverter. I only got over 30 amps from solar around lunch time. Most of the day and all night I was losing. Gottaluv propane mode for off-grid!

Yeah, yeah, all you "experts" tell me something won't work, yet, I'm still doing it. The problem must be with me.

Chum lee

DrewE wrote:

Chum lee wrote:

Yes, I can read. (thank you!) Yes, absorbtion refrigerators ARE very efficient, (you are incorrect) that's why they are used in RV's in the first place. Ooops, ya missed that one didn't you?

Absorption fridges are quite a bit less energy efficient than compressor-based residential fridges (in terms of total energy use). The main reason they're used in RVs is that they use an energy source that is much more easily stored compactly: propane has a much higher energy density than electric batteries. A residential fridge will use somewhere in the rough vicinity of a third the power that an RV fridge will use if both are operated from AC power.

DC-powered compressor fridges are usually pretty efficient...and not all that inexpensive. Their DC consumption is higher than an absorption fridge's DC power use in propane mode, of course, since it's providing the actual energy to cool rather than just powering the controls.

I agree with you. Propane is much more energy dense than storage batteries. (at least right now) In an RV, you have to deal with what you have based on where you are. (energy wise) With a 2/3 way absorbtion fridge you have the flexibility of using gas or electric. IMO, you can talk about energy efficiency all you want. Depending on what you are doing (with your RV) if the most efficient/economical source of energy isn't currently available, IMO, it's kind of idiotic to speak as though it is. I boon dock off grid a lot. I like my solar panels. Are they perfect, . . . NO. Do they substantially reduce the need to run my generator (which produces electricity at about $.80/kwh) YES they do. Do I sometimes plug in to full service campgrounds, (electricity at $.15 to $.25 /kwh) Yes I do. Do I suggest how you should use your RV, . . . NO, I don't.

Chum lee

I tried to run my absorption RV fridge on 120v this summer off inverter with 800+ watts of solar flat on the roof in good sunshine. It didn't work out. 325w on 120v was 30 some amps draw by the inverter. I only got over 30 amps from solar around lunch time. Most of the day and all night I was losing. Gottaluv propane mode for off-grid!

Chum Lee,

The absorption fridge in my class C uses 5.7 KWH per day (measured with a kill-a-watt meter). That is with an ambient temperature of about 68 f (20 c).

Running it from solar would require 1100 watts of panels and 4 SiO2 batteries (6 would be better).

It would use less 120 volt power to run a residential fridge.

Duty cycle is 2:3 (measured).

Chum lee wrote:

Yes, I can read. (thank you!) Yes, absorbtion refrigerators ARE very efficient, (you are incorrect) that's why they are used in RV's in the first place. Ooops, ya missed that one didn't you?

Absorption fridges are quite a bit less energy efficient than compressor-based residential fridges (in terms of total energy use). The main reason they're used in RVs is that they use an energy source that is much more easily stored compactly: propane has a much higher energy density than electric batteries. A residential fridge will use somewhere in the rough vicinity of a third the power that an RV fridge will use if both are operated from AC power.

DC-powered compressor fridges are usually pretty efficient...and not all that inexpensive. Their DC consumption is higher than an absorption fridge's DC power use in propane mode, of course, since it's providing the actual energy to cool rather than just powering the controls.

Gdetrailer wrote:

Chum lee wrote:
I don't understand why you are doing what you are doing. In the larger scheme of things, the electricity (12 volt) to run the board/valve is negligible. If you are going solar, why not consider running the fridge on 120 volts through a 120 volt inverter, solar panels, controller, and a battery bank, (probably 4-6 volt wet cells) eliminating the need to use propane at all? (at least for the fridge) IMO, you could do that with 3-140 watt panels (if you have room) and have plenty of solar power for most everything else too. You don't state what vehicle you have. (maybe the clue lies there)

Chum lee

You are mistaken there for sure.

OPs RV fridge uses a very inefficient "absorption" system which relies on gravity to make things happen instead of a quicker compressor.

This type of fridge requires considerable amount of heat input to cool a very tiny space..

The RV absorbsion fridges use a 325W or so 120V heating element..

Gonna take a huge solar panel array to make up for a 325W heating element.. So, instead of camping with a 100W-300W solar array, they would need to increase that to 600W, possibly 1,000W of solar and add quite a few batteries to their system..

Now, IF you were talking a 120V compressor fridge then it IS possible to work the solar angle with not much investment since fridge compressor uses 90W at 120V instead of a RV fridge heater of 325W..

BUT, we are not talking a compressor fridge here.. In this case, using propane is the better and wiser thing to do instead of carrying a thousand watts worth of panels.

Keep in mind that with most modern RV fridges, the control board does need 12V and that IS what the OP was inquiring about.

Yes, I can read. (thank you!) Yes, absorbtion refrigerators ARE very efficient, (you are incorrect) that's why they are used in RV's in the first place. Ooops, ya missed that one didn't you? I do understand how they work. When in electric mode, the 325 watt 120 volt heating element operates on a duty cycle, (just like the propane flame) far less than 100%, unless it's in start up cooling mode or you keep the refrigerator door open. You will need more than the standard battery (2 batteries) bank to insure reliability over the night and in times of cloud cover. For extended periods lacking solar, you can simply switch back to propane, if necessary. Please excuse me while I go get a cold beverage from my solar powered Dometic 2652 absorbtion fridge, which, . . . . doesn't work.

Chum lee

I see the replacement for a 2310 is a 2351. (or 2354?) here is one for sale. No idea if there are better deals. I did see another for $1,000 so prices vary for sure.

https://www.rvpartscountry.com/Dometic-RM2351-Americana-RV-Refrigerator.html

BFL13 wrote:
The 1991 TC we got recently has a brand new 2410 the previous owner had put in, that does not use 12v. The OEM 2410 lost its ammonia (smelled really bad he said). So you can still get them.

The 2410 is 3" taller and deeper and 2" wider than the 2310 so it would not fit in my RV.

http://w2.distone.com/bradstrailer/downloads/RefrigeratorReplacement.pdf

I used to play around with watt meters. But i fried them. Have you ever heard of a technical tap? Wonder if you could smack it around a little. Get them solder joints back to touching. (park jokes and part serious)

From what you guys describe is sounds like the clamp meter wont be accurate. Hopefully one of my watt meters still works down at low rating.

Just realized i have a Dometic 2852. Mine cycles a good 8 times a day. I have a thermometer that forms a graph so its easy to count the peaks. Curious like you how much the actual usage is over 24 hours. I can find out for this model. Hope its similar to yours. Ballpark i guess?