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Old 04-20-2022, 06:57 PM   #41
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[QUOTE=Civilguy;839097]Yes, it only makes sense that the compressor fridges would make units which could replace absorption units.

Now Iím having one of those forehead-slap moments; the compressor fridges donít need to vent all the heat thatís used to boil the ammonia solution, and only minimal amounts associated with the inefficiency of the compressor.
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If it sounds too good to be true, it probably is. The compressor fridge has evaporator and condenser coils. The evaporator coil is inside and absorbs heat to cool the air in the fridge. The condenser coil on the outside (sometimes built into an exterior surface) emits heat into the air in the RV. And yes, the compressor also emits some heat. So it is important to have good circulation in the compressor and condenser coil area. Many RV owners add extra fans and vent space to accomplish this.

The heat you are removing from the refrigerated space does go directly into the RV interior but it is pretty insignificant compared to the large amount of heat that conducts through the lightly insulated walls and generally uninsulated windows that are part of the typical RV.
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Old 04-20-2022, 10:47 PM   #42
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[QUOTE=wbullivant;839396]
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Originally Posted by Civilguy View Post
Yes, it only makes sense that the compressor fridges would make units which could replace absorption units.

Now Iím having one of those forehead-slap moments; the compressor fridges donít need to vent all the heat thatís used to boil the ammonia solution, and only minimal amounts associated with the inefficiency of the compressor.
.................................................. .................................................. ......

If it sounds too good to be true, it probably is.
In this case, it is true. No huge upper and lower vents to get rid of the heat from the absorption fridge. Mine vents to the trailer interior. And no combustion products get vented. The small amount of heat delivered helps in winter and hurts in summer, so it averages out and is not enough to worry about. And with no large holes in the exterior, the trailer insulation can be a lot better.

Of course, the heat expelled by the fridge is more than the energy required to run the compressor because of the COP of the heat pump system, but I don't know what the COP is of the typical compressor fridge.
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Old 04-20-2022, 11:04 PM   #43
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When plugged into a 120V AC power source, your converter (charger) will both charge the battery AND supply the 12V DC necessary to run the refrigerator. The only time you will discharge the battery is when you are not connected to an AC source.

As long as the converter will have the power to run the frig
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Old 04-21-2022, 06:03 AM   #44
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Just to summarize my thoughts on this topic:

Solar + LiFePO4 + CompressorFridge = Perpetual Motion Machine
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Old 04-21-2022, 12:14 PM   #45
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As long as the converter will have the power to run the frig
He is asking about a compressor refrigerator. I doubt there are many converters that can't supply the 6 amps or so that a efficient compressor refrigerator draws.

Now for those with absorption refrigerators, I'd never run them on DC although there are folks that run them on DC while driving. Some will end up with dead trailer batteries...
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Old 04-21-2022, 06:41 PM   #46
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He is asking about a compressor refrigerator. I doubt there are many converters that can't supply the 6 amps or so that a efficient compressor refrigerator draws.

Now for those with absorption refrigerators, I'd never run them on DC although there are folks that run them on DC while driving. Some will end up with dead trailer batteries...

He was talking about the ones that run on DC or that is including in the thread here. I didn't say inverter I said converter. And the talk is about running on DC and then using a RV converter to provide the DC power when on AC. None of that would seem wise to me. It sure is going to take a lot more than 6 amps dc to run the compressor. And likely more than many AC to DC converters are rated for. If you are drawing more than the converter can provide you will have a problem.

I have always used propane on my frig when not on AC power. If I am running on a generator most of the time I use AC. But some times I only cycle the generator once in a while to recharge the battery and then I use propane. That is the advantage of a absorption unit. It does not care where the heat is coming from. If it has heat it can provide cool. I have even seen a hair dryer used on a frig to maintain medical stuff when the propane was out and the normal AC element was not working.
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Old 04-21-2022, 08:22 PM   #47
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My 10 cu ft Furrion compressor fridge uses about 10 amps DC when running. It runs, when at a stable temp inside, about 10 minutes per hour.

This is a very easy demand to meet with DC. When plugged into shore power and charging batteries, there will be a little inefficiency in the system, but there is so much power available from the 120 VAC system that it will go unnoticed.

The best way to run a DC compressor fridge is from solar. No other energy source is needed, neither propane or shore power. And while driving, the tow can be charging too, if needed.

My trailer has been sitting outside and/or traveling for over a month. It has not been plugged in, we've used no propane except to cook, and the fridge has been running the whole time. The freezer is sitting at about zero.

We don't turn the home fridge off when we travel, and we don't normally turn the trailer fridge off when we are home. And I don't plug in unless the trailer is inside and we want to use power.
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Old 04-22-2022, 12:26 AM   #48
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Having spent week or more in the boondocks running on propane and lead acid batteries I can attest that the system worked. I did it before solar became affordable by running a large 12 volt alternator every couple or three days for a battery charge. Ask me how I know deep cycles charge slow irrespective of charge provided and I'll tell you about optimum rpm's for lower noise but better charge by leaving on for hours.

So absorption fridge using propane and 12 volts with solar will clearly work and might explain why so many RV's come with 3 way fridge and solar as an option to charge the typical lead/acid battery. Remember the 3 way has an electric circuit so requires 12 volt sufficient to keep it working, I think most new ones beep at you if voltage drops too low.

Are there other options such as high efficiency absorption refrigerator, or different battery technology? Yes certainly. I think one is smart to consider those when buying new. No point in paying for a 3 way fridge if you will get better use from buying something else not offered.

Same could be said of lithium batteries. Buying a new battery that one will replace with a rather expensive battery using a different technology not be cost effective. One does have to consider ones own usage in terms of how often the investment will get used and in what conditions.

Wife has no interest in week or two in the boondocks any more and with 100 watt solar I don't need to supplement power with a generator. Sits in the garden shed nagging me to start every so often and keep it functional.

So one has to ask how often will battery be used. And will it be used in situations where I will benefit from investing in Lithium or other more expensive battery technology. Or will a supplemental solar panel be more cost effective. Or am I expecting weekend not week long use so I don't need to worry about it. Any battery will do what I need it to.

Same for the fridge. Key question there that I do not know a definitive answer to. High elevation and propane fridge functionality. I have used it in Colorado but never stayed long enough in higher elevations to determine propane power was effective or not. I kept blue ice packs in freezer so it was good for a day or so just on those acting as an ice box. Don't recall if propane kept those solid or not. Food was ok and seemed cold enough so didn't check. The ambient temps were not high, especially at night that can make a difference too.

Any refrigerator will use more power in hotter environment. They are after all pumping heat to be absorbed by ambient air. I seem to recall an old rule of thumb was a propane fridge in decent condition could drop the temperature by maybe 50 or so degrees. At 90* air temp I could maintain high 30s for fridge temp. based on experience. Don't know if at 100 maybe it would struggle unless more air flow was provided to the exhaust side of the heat exchanger. I don't know. I do know computer 12 volt fan was and is a common mod to add more back side air flow.

Freezer could do ice but ice cream was a bit iffy, wouldn't melt but not rock hard. At least the settings I used. Didn't want too cold in food compartment and one setting for both freezer and fridge. Bag popsicles were better choice. Slide in beside blue ice on one side of freezer. Meat on the other and kids were happy. Meat didn't spoil and generally had ice crystals if not frozen solid.

A week at mountain elevations above say 7000 feet with some hot weather I don't have any experience to say propane can keep up. I use 7000 feet because that is max elevation for furnace low oxygen sensor to not get tripped and shut off furnace. Since that is simply a heat sensor that won't stay hot enough if pilot flame is too small from lack of oxygen I have to think the flame from a propane fridge would also be smaller and possibly less effective. It does however run 100% of the time on so little propane that long stay isn't even an issue with a pair of tanks or even one unless one uses the furnace a lot and/or cooks inside.

So anyone know propane fridge performance at high elevations? I'm sort of curios now that the question has been asked. I learned about issues of desert fridge use (locate on shady side was big take away) from members here. Interested in how propane works at 7k plus elevations or at least higher 5 and 6 thousand foot.

There is resale value to consider too. I'm not sure if being "standard" fridge that factories tend to install will be an advantage on resale or if having a compressor fridge and possibly (or probably) enhanced solar and/or battery set up to accommodate it will be a better selling point. Might depend on how well you can sell the advantages over the "stock" manufacturer choices to a buyer.

In the end though it comes down to the individual use case. How you plan on using your camper. How often and in what situations that will determine value of your choices. If either will do the job then one might want to figure the difference by the number of uses in X number of years to see how little or much the purchase of own compressor fridge will cost above the stock fridge.

Same for batteries and also for what you want for solar. Where and how often has a significant impact on this choice too. If it rains daily 300 days a year (yes great north wet I mean you) or is desert with an ambient relative humidity in the teens. Or desert mountains that tend to see rain for short periods but fairly often.

All comes down to what you need a solution to do. How much gain does one get for spending additional money on that solutions. This give you a "value" and if you want you might consider resale value as a side consideration.

Lord knows bathroom or no debate is the same as this. Will I use it enough to be worth the space the way I camp? Or will it be where I store junk in a badly designed closet? Will it attract more buyers at a better price or not as a follow on consideration.

Last camper answer was no. This camper as we get older.... answer tends toward oh heck yes bathroom. We have boondocked less and done more short trips now than we used to with the kids or as a couple get away. House to self makes those couple retreats less special I guess. And getting kids together is not as easy when they have jobs and kids. So when replacing old camper and considering bathroom this last time and based on current use cases bathroom was a yes and more batteries and gas powered charging or dual 30# tanks were not required. Never had air conditioner, do now. Maybe 1/2 dozen times in over 40 years I would have really liked to have it. Comes fairly standard so I may use and it will probably help resale value.

3 way fridge was normal option to find used. 100 watt solar should be plenty to keep it working on propane and dual 20# tanks with a cut over were able to address all my use cases. If I do a long boondock trip in the Rockies (which I may well do) I could reconsider batteries. Already bought the fridge so will use on propane. If propane doesn't work well enough I have also done long backpacking trips. I know I can survive on tuna and chicken packs, pasta and trail mix for at least a week. Salad dressing and seasoning for the pasta. Not bad, really. Some dried fruit is a nice addition, oh yeah instant oatmeal with some jerky is good for a breakfast. So a fridge isn't absolutely essential, just darn useful to making spouse happy. A condition I can attest improves the scenery and all other aspects of the camping experience. Stuff melting or getting "iffy" is going to do the opposite so I would say anything that works is a good choice. Best choice is up to how you value any gain the addition cost provides.
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Old 04-22-2022, 12:56 AM   #49
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Freezer could do ice but ice cream was a bit iffy, wouldn't melt but not rock hard.
Anti-freeze is one of the ingredients in ice cream to keep it from freezing rock hard. It's not the same stuff you put in your radiator.
U.S. FDA allows propylene glycol to be added to a large number of processed foods, including ice cream, frozen custard, salad dressings, and baked goods
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Old 04-22-2022, 01:09 AM   #50
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God when I take this one medication I don't sleep easily. I also apparently type a lot in a Hunter S. Thomson sort of manner.
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Old 04-22-2022, 01:11 AM   #51
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Anti-freeze is one of the ingredients in ice cream to keep it from freezing rock hard. It's not the same stuff you put in your radiator.
U.S. FDA allows propylene glycol to be added to a large number of processed foods, including ice cream, frozen custard, salad dressings, and baked goods
I recall finding out that some "no added preservatives" referred to the ice cream but ignored the container being treated inside with stuff to extend shelf life and prevent ice crystals from forming. I was shocked, shocked I tell you. Or not.
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Old 06-25-2022, 09:56 PM   #52
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We live in Colorado and frequently camp at or above 9,500 ft. So far no problems with a fridge on propane or having any issues with propane appliances including the water heater or furnace.
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Thanks, that sounds promising! The manual for our Dometic DM2663 refrigerator says we might be better served by operating on shore power at 5,500 ft and above and we'll be at 8,900 for a few nights without shore power. From what I have seen, the issues with operating at high elevations seem to be hit and miss with different folks.
We spent 22 nights above 5,000 ft. on our recent trip, including 10 nights above 5,500. We had no problems with the Dometic DM2663 three-way absorption fridge in our Escape 21.

That included three nights at 7,750 ft. running the fridge on AC power, followed by three more nights running on propane at 8,900 ft. in Timber Creek campground. This leg of the trip also included transiting from Estes Park on Trail Ridge Road, which tops out at over 12,000 ft.

The fridge worked great throughout the whole trip. The freezer was 0 to 10 degrees Fahrenheit and the fridge compartment was in the 30's on setting 3 of 5. Ambient temperatures were pretty moderate at these higher elevations, with highs in the 70's.

We then spent four nights at elevation 6,200 with three days of high temperatures up to 98 degrees. Again, the fridge worked fine, this time on AC power.

I have not modified the installation, and there are no accessory cooling fans. It's nice to have it work so well as-delivered from the factory, as I had to spend a fair amount of time improving the fridge installation in our Casita.
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