Refrigerator draw on LP mode

[Whangler]

I'm evaluating my total amp draw in order to properly size a new solar system with lifepo4 batteries and all that entails.

My Fridge is a Norcold N821 2-way. The decal inside says it draws .8 amps dc. Over a 24 hour period, that calculates to 19.2 amp hours. I thought the draw was minimal on LP mode. Can 19.2 ah per day be right? Or... does it only consume 8ah when the igniter is running? If so how do I figure amp draw over a 24 hour period?
Thanks!

[pianotuna]

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).

[DrewE]

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.

[Chum_lee]

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

[BFL13]

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

[steveh27]

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

[wopachop]

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?

[BFL13]

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.

[steveh27]

Good luck with your fridge,

My 1997 Xplorer 230XL has a Dometic RM2310 fridge which draws no 12v power when on propane making it perfect for boondocking which is most of what I do. When I had a rust breakage problem with the flue and piezo lighter lining up, I checked into a new replacement, but with their electronic controls running on propane would draw 1.5 - 2.5 amps, way too much for my boondocking.

I took it to an RV repair shop & they refused to touch it. I was able to fix it myself and I am back in business. I wish Dometic still made a model without all the electronic stuff just for boondocking. I hope I can keep it going.

[pianotuna]

Duty cycle is 2:3 or on for 40 minutes each hour.

My parasitic loads amount to 35 amp-hours per day. (not including inverter)

[Gdetrailer]

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 modener RV fridges, the control board does need 12V and that IS what the OP was inquiring about..

[Chum_lee]

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

[Gdetrailer]

BFL13 wrote:
Had that fridge in our 5er. Measured 51AH in three days of fridge on gas, off grid. So 17AH a day. This was with ambients around 75F day. 55F night, no shade, nice weather. That was while we were away for three days, so no door opening.

Divider HEATER element was killing you at .25A.. in 24hrs that is 6Ahr and 3 days that is 18Ahr out of your 51Ahrs..

Some fridges that have it have a switch to allow you to disable it..

It is there to stop condensation around the door..

[RJsfishin]

Yes, figure 1.0 amps. I mean it aint like your going to screw up and get too much solar,.......it aint gonna happen !

[time2roll]

You may as well get out your meter and measure as to include everything. My trailer idles at 500 milliamps with the fridge propane cycled on.

[BFL13]

Had that fridge in our 5er. Measured 51AH in three days of fridge on gas, off grid. So 17AH a day. This was with ambients around 75F day. 55F night, no shade, nice weather. That was while we were away for three days, so no door opening.