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!

[allen8106]

My Norcold draws .5 amps when on propane.

[pianotuna]

Chum lee wrote:
Thanks for your post. I do appreciate what you do. I am a professional paid engineer. (and a **** good one at that) I deal with reality everyday. When I say/suggest my solar panels generate 140 watts, I'm not talking about the manufacturers published wattage, I'm talking about what they actually do, . . . sitting here, right now. I keep track. Currently, I have 3-240 watt Kyocera panels flat mounted on the roof, an MPPT controller and a 1000 watt PSW inverter. I'm not giving away all the details of what I do to make it work. Hire me if you want to know.

Chum lee

Hi Chum lee,

I'd love to have hired you in 2005. But....unless you have a Tardis we could use I guess that won't be happening.

Using the 'usual' 5 hour number the solar harvest for the system is about 3600 watt-hours. It may be that your duty cycle on the fridge is lower than mine.

Iirc the Kyocera are a pretty high voltage panel. I suspect that extends the number of harvest hours to a number greater than the 5 hour "guesstimate".

Thanks for your reply.

[MrWizard]

I have used LP cooling and 120v cooling
An LP absorption fridge uses a small flame and less l.p. Than cooking or heating or the water heater, but it is still the same amount of energy btu's as produced by the electric heating element, energy use wise, RV absorption fridge can not compare to a compressor fridge that uses 1/3 the amount of energy for better cooling effectiveness , my previous RV had a 120v compressor fridge powered by inverter, and I was very happy with it
This RV has a side*side 2 door RV fridge and I only use the LP setting, I will switch to 120v only if I run out of LP because I wasn't paying attention to my use, at that point I use the inverter to maintain the fridge while I make an Emergency run to the LP fill location 7 Miles to the open all night truck stop, with lowest l.p. Price available in the area,
No absorption is not cost energy efficient when compared to compressor fridge operation costs
L.p. Is energy dense , creating electrical energy for RV fridge operational heat is not efficient,
Can it be made to work ? Yes in some cases
But not for every case

[Chum_lee]

pianotuna wrote:
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).

Thanks for your post. I do appreciate what you do. I am a professional paid engineer. (and a **** good one at that) I deal with reality everyday. When I say/suggest my solar panels generate 140 watts, I'm not talking about the manufacturers published wattage, I'm talking about what they actually do, . . . sitting here, right now. I keep track. Currently, I have 3-240 watt Kyocera panels flat mounted on the roof, an MPPT controller and a 1000 watt PSW inverter. I'm not giving away all the details of what I do to make it work. Hire me if you want to know.

Chum lee

[steveh27]

BFL13 wrote:

steveh27 wrote:

BFL13 wrote:
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

I have researched that replacement before I repaired mine. Due to it's electronic control panel when on propane it does draw 1.5 - 2.5 amps, way too much for my boondocking. My 2310 draws no power on gas.

In your 1997 Class B I can imagine the problem. (you can't make the fridge space bigger like with some in RV cabinet areas) Let's hope your repair lasts out the time you will own that RV. If not, a 2351 might be the only choice or else luck in finding a good 2310 that is from a unit being "parted out".

If you are forced into a 2351 and need more AH with no room for more batteries, would an SiO2 solve the problem? It can operate down to a very low SOC so you get more AH. Same idea as a Lithium but able to stand the cold and is a lot cheaper and no BMS. It still costs more than ordinary batteries though.

I didn't check if Norcold makes a no 12v model like the 2310 that would fit in there. Beats me. Always some darn thing with RVs!

Thanks BFL for the reply. I did get 2 100 AH Lifepo4 batteries, but have not boondocked with them yet due to my health issues. I hope to start using them in April, 2021. I would like to find a 2310 as a replacement if needed..

[BFL13]

steveh27 wrote:

BFL13 wrote:
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

I have researched that replacement before I repaired mine. Due to it's electronic control panel when on propane it does draw 1.5 - 2.5 amps, way too much for my boondocking. My 2310 draws no power on gas.

In your 1997 Class B I can imagine the problem. (you can't make the fridge space bigger like with some in RV cabinet areas) Let's hope your repair lasts out the time you will own that RV. If not, a 2351 might be the only choice or else luck in finding a good 2310 that is from a unit being "parted out".

If you are forced into a 2351 and need more AH with no room for more batteries, would an SiO2 solve the problem? It can operate down to a very low SOC so you get more AH. Same idea as a Lithium but able to stand the cold and is a lot cheaper and no BMS. It still costs more than ordinary batteries though.

I didn't check if Norcold makes a no 12v model like the 2310 that would fit in there. Beats me. Always some darn thing with RVs!

[steveh27]

BFL13 wrote:
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

I have researched that replacement before I repaired mine. Due to it's electronic control panel when on propane it does draw 1.5 - 2.5 amps, way too much for my boondocking. My 2310 draws no power on gas.

[pianotuna]

Chum lee,

Power is $0.147 cents (Canadian) per KWH, but my cost is zero at local campgrounds, as none of them meter it.

Propane is quite expensive here. I think about $1.29 per liter (Cdn). It has been over 15 months since I last purchased propane as I'm no longer full time--and covid has played havoc with travel plans. I may be out to lunch on the price per liter.

How many watts is your solar system? Charge controller make and type?

[Gdetrailer]

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? 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

Hate to tell you this one, my Home fridge conversion uses VASTLY less energy than ANY RV absorbsion fridge, period.

I HAVE measured not only the wattage drawn while running, but the startup surge and the overall run time per hr.

Compressor fridges do not run 100% of the time 24/7, they too CYCLE.

Mine averages only 22 minutes PER HR of compressor run time for 60F to 110F ambient temps.

Draws max of 90W running and startup surge lasts micro seconds.

The inverter I use a Tripplite PV1250 has a load sense control which turns the inverter on/off with 120V load demand. I ahve mine setup that the fridge light will turn the inverter on when the door is opened and off when the door is closed. Inverter draws less than 100 ma from the battery while it is off which is less than a RV fridge control board (which a RV fridge control board runs 24/7).

With the way I have setup my trailer, I can easily run the fridge, all the lights, some entertainment for many hrs plus the furnace the entire night when needed on only ONE pair of 6V GC2 batteries for 24hrs without needing to recharge.. And no, I do not have any solar either.

You will never, ever do that with your idea of running a RV fridge with a 325W heating element, period.

Absorbsion cycle is HIGHLY INEFFICIENT, you are wasting a lot of energy in heat going up the stack (325W worth). RV fridges are also very slow at recovery which means you open the dor even for a couple of seconds it will take an hr or more to recover from that event wasting more energy in the process.

My compressor fridge on the other hand is only wasting a mere 90W of energy in heat and it recovers very quickly when the door is opened unlike a RV fridge which can take hrs to recover.

You have not really done any real research other than assumptions, I have done my research, I have done my homework.

And by the way, my first trailer had a RV fridge, couldn't hold a candle to my home fridge when it comes to holding a steady temperature.. The RV fridge I had, would get a good roasty 50F in daytime temps of 100F and at night when the outdoor temps dropped to the 70's well everything would freeze solid.. Had to chip the milk out of the bottle.. And carrying ice cream was a no no, don't like melted ice cream during the day that gets refrozen at night..

Don't have that issue with my home fridge, keeps a nice constant 34F-36F in the fridge and the freezer keeps my Ice cream rock hard 24/7 as the way it should be..

Come over to the "dark side", you will never ever want another RV fridge once you try a real fridge.

[Chum_lee]

pianotuna wrote:
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).

Don, thanks for your post. Your are a little bit north of where I live. (South/West USA) The solar angles vary greatly. Of course, you need more solar panels in your location than I do.

You haven't mentioned what you pay for propane/electricity so can't say as much as I would like to in this format.

Chum lee

[BFL13]

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.

[Chum_lee]

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

[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

[BFL13]

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!