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Old 05-16-2018, 08:53 PM   #21
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Default Propane...I'd rather save my house batteries for something else and I have a solar

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Absorption frigs are probably the least efficient refrigerator you can get. Sure, they work better on propane than on 110v or 12v, but that is only because you can get more heat out propane than you can out of either of the electric ways. All that heat goes out the chimney along with a little bit of the heat from the frig. On DC, they use 5 times the power of a compressor frig for really weak cooling capacity.



IMO, there are many more compromises with a 3way frig than an compressor version. Leveling, outside temperature, fumes, are just a few. At 100*F you won't keep food cool in almost all of them. About the only compromise with a compressor frig is making the necessary power availability changes, which are normally not all that much.


I don't think I have ever seen anyone go back to a 3 way once they had switched to a compressor frig.

Well.. if and when my 3 way fails... I will go get another 3 way....probably with an automatic switch for whenever I plug into shore power.. right now, I have to manually switch it.


Only decision will be either Dometic or some other brand...
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Old 05-16-2018, 09:35 PM   #22
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I found two ideal setups (IMHO, of course) for a class "B" refrigerator:

The first is a propane fridge, but one that requires no battery power to run, and uses a pilot light. The reason why this is useful is because it separates it from everything else, guaranteeing your beer will be cold no matter what. Bonus points if it can be run by 12 volts or 120 volts, so propane can be shut off while going down the road.

The second is a marine grade fridge with a Danfoss compressor. The biggest advantage of going this route over a cheap dorm fridge is efficiency. Even 1-2 amps can mean a significant difference for sustainability. The upside of this is the fact that you do not need ventilation, other than the place for the exhaust inside, and it cools quickly. The downside is that it requires a decent solar system and battery bank.

I'm not sure which is the best of these scenarios. Maybe someone can make a fridge that has both absorption and compression coils so it can efficiently run from solar, and at night, use absorption cooling to lesson the load on the batteries.
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Old 05-16-2018, 09:50 PM   #23
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I'm with Booster. I can't imagine anyone who has ever actually experienced both ever even considering an absorption unit. In practice, it is a night and day difference in performance.
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Old 05-16-2018, 10:34 PM   #24
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I'm with Booster. I can't imagine anyone who has ever actually experienced both ever even considering an absorption unit. In practice, it is a night and day difference in performance.
It is quite simple in few words. THE reason for an absorption refer is Not Enough Reliable electrical power.

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Old 05-16-2018, 11:20 PM   #25
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Default Reliable or not... when you're out of power, it's a problem

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It is quite simple in few words. THE reason for an absorption refer is Not Enough Reliable electrical power.

Bud

Regardless, I don't want my food to spoil while I'm out boon docking because I ran out of power...

Sure, I have a generator.. and solar panel... but, if I don't have to run the generator... and there's restrictions on that … it's one less thing to worry about...


And, I have two AGM deep cycle 6 volt marine batteries in series.

Just me...
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Old 05-17-2018, 12:15 AM   #26
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I don't want my food to spoil
Oh, I've had plenty of spoiled food over the years. It stopped when I got a compressor.
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Old 05-17-2018, 12:27 AM   #27
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Oh, I've had plenty of spoiled food over the years. It stopped when I got a compressor.
+1. That's why we got rid of both of our 3-way fridges. They simply didn't work as advertised. I was a die-hard 3-way advocate until I discovered this.
The Vitrifrigo works just as well at high-90s exterior temperatures as it does at any other condition (although it does cycle harder).

It is possible that many people don't know how bad the 3-ways really are (hence my link to the thread above where owners took a quantitative approach to evaluating them). The van-sized Dometics don't come with either thermostats or thermometers of any sort. What does that suggest, when the manufacturer produces a refrigerator that is not capable of telling its own temperature? It's sort of like a clock that doesn't tell time.

I am not sure why anyone would be penny wise and pound foolish on this issue. Good refrigerators cost, but so do inverters of any decent capacity, which is what it would take to run a dorm fridge. But, to each their own.
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Old 05-17-2018, 12:30 AM   #28
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Oh, I've had plenty of spoiled food over the years. It stopped when I got a compressor.
Yes, I understand... Sorry...

We try very hard to avoid this....I guess anything can happen....

I'll do some more research on the compressor refrigerator idea....

Actually, I floated this idea to my RV shop....and they said..why would you not have the 3 way......

OK.. time for independent investigation....
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Old 05-17-2018, 12:30 AM   #29
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Dug up the test,
interior van temp 88°,
around 2.5 gals of water bottles in freezer,
inverter and freezer on cycle is 00:07:14,
inverter and freezer off cycle is 01:41:02,
freezer data plate, 115v, .89 amps, 95 watts,
I'll let others do the math, but in my situation this is cheap and it works.
Great info! I too already have an expensive 12V compressor fridge in my current rig and won't be changing it. However, if I was building a new van - with a lot of Lithium storage - this is what I would be doing. Having this data is useful. Would be good to add some specs on the fridge (make, model, size, etc.)

The other question that was discussed in theory (but not tested AFAIK) was regarding a cheap but efficient 110V water heater like this one;
https://www.bosch-climate.us/product...mini-tank.html
Some opine that this would be too power intensive; but I think it might not be too bad as long as it was insulated enough so that it didn't come on often. In fact, one guy I spoke with at a campground had one of these connected to an inverter and only ran it when his van was running - he said it worked fine for most of his needs (mobile vandweller).

You would save a lot of $$ and complexity to just have lots of battery storage and a big inverter and run everything on 110V, at least that's what I was thinking...
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Old 05-17-2018, 12:38 AM   #30
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Regardless, I don't want my food to spoil while I'm out boon docking because I ran out of power...

Sure, I have a generator.. and solar panel... but, if I don't have to run the generator... and there's restrictions on that … it's one less thing to worry about...


And, I have two AGM deep cycle 6 volt marine batteries in series.

Just me...

Prediction: If you replace your absorption unit with a high efficiency compressor unit, you will periodically wonder what took you so long. If the compressor reefer is a Nova-kool with dual compressors providing totally independent operation of the fridge and the freezer, it will be obvious from your perpetual grin.
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Old 05-17-2018, 12:53 AM   #31
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I'll do some more research on the compressor refrigerator idea....

Actually, I floated this idea to my RV shop....and they said..why would you not have the 3 way......

OK.. time for independent investigation....
Does the guy at your RV shop have an RV?

Honestly, nobody is trying to give you a hard time. Folks are just speaking from experience. Deciding between a absorption and a compressor fridge is kind of like deciding between a slide rule and a pocket calculator. Both can do multiplication, so...
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Old 05-17-2018, 12:57 AM   #32
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Oh, I've had plenty of spoiled food over the years. It stopped when I got a compressor.
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Old 05-17-2018, 01:50 AM   #33
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Does the guy at your RV shop have an RV?

Honestly, nobody is trying to give you a hard time. Folks are just speaking from experience. Deciding between a absorption and a compressor fridge is kind of like deciding between a slide rule and a pocket calculator. Both can do multiplication, so...

Avanti, sure, I understand and appreciate your input... really....
I'm pretty new compared to a lot of people on the forum.......

Couple of things; I don't get technically involved in working on my rig.. but, I appreciate advance technology and expect things to work as intended.....

My rig is a 2012 Roadtrek RS Adventurous.. and it came standard with a Domestic 8501 refrigerator... I'm sure it's original... Coach was lightly used..26,000 miles, maybe 15 or 20 hours on the generator when I purchased it May 2017...I now have 41,000 miles on the rig... SO, I'm using and enjoying it...

Except for really "hot weather" and it certainly gets hot here in LA...the refrigerator works fine...we took the coach across the USA last fall for 3 months.. everything was fine..

I'm getting the coach serviced right now and asked them just to look at the refrigerator to make sure it doesn't need anything... somewhere I heard that neglected RV propane refrigerators are the number one cause of RV fires...OK....

Now, in terms of how we use it...I don't live in my RV....the propane tank lasts about one month..and I switch between propane and electric when we're plugged into shore power..
My understanding is that when you are using propane..it's pretty efficient and the heat from the unit is discharged out of the vehicle through an outside vent....the compressor refrigerator has a fan that causes heat build up inside the vehicle...

And a a Danfoss system on DC power is a compromise between the propane and home style refrigerator you might typically find ..and generates a lot of inside heat...The Danfoss is more efficient than the AC refrigerator... both require more electric power...
I'm sure that the Danfoss is not particularly cheap like your typical AC refrigerator unit...

A lot of people still think that the propane is the gold standard... maybe Danfoss is changing that???

In any case, again, I'm mostly home... and the rig system is a secondary refrigerator .. but, I want it to work fine....we usually chill it down overnight then stock it early before we go....

YES, the people who own the RV shop.. and it's a family owned business have been there since 1981..they have RVs...and I wouldn't just dismiss something they told me...

I'm going to have them look to see if my refrigerator needs anything.. just for safety....

I'm getting a major suspension upgrade on the rig... new KONI FSD shocks, new upgraded anti sway bar and a track bar... plus a wheel alignment... should make the ride and improve control immensely... another thread is out there on this.....

They told me that if I should ever need to replace the refrigerator... expect to pay around $1,500.... They're not inexpensive... but, I'm finding out that everything is extremely expensive on the RV....my boat on wheels
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Old 05-17-2018, 02:19 AM   #34
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A compressor frig can have the venting either inside or outside. Most of the conversions from 3 way units, like ours, are vented outside through the original frig vents so no heat inside at all. Even if it were vented inside, as I am sure others who have them vented inside will confirm, they really don't generate much heat at all. Probably less than a 10 watt light bulb.
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Old 05-17-2018, 02:29 AM   #35
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My understanding is that when you are using propane..it's pretty efficient and the heat from the unit is discharged out of the vehicle through an outside vent....the compressor refrigerator has a fan that causes heat build up inside the vehicle...
As stated above, propane units are horribly INefficient. The only reason that they are practical is that propane contains a lot of energy, so there is lots to waste.

As for compressor fridges heating the van: this is true if you choose to install the compressor fridge without outside vents. In that case, it heats the van in exactly the same way that your home fridge heats your kitchen: Theoretically true, but in practice it is negligible. You are not burning propane, there isn't much heat.

BUT: if you were REPLACING an absorption unit with a compressor fridge, you would presumably put it in the same place, and that place will already have vents, so the heat will exit the van in exactly the same way that it does now--except that there will be a LOT less heat to vent.
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And a a Danfoss system on DC power is a compromise between the propane and home style refrigerator you might typically find ..and generates a lot of inside heat...The Danfoss is more efficient than the AC refrigerator... both require more electric power...
What is the compromise? A good compressor fridge works exactly as well as your home fridge. If you want rock-hard ice cream, you can have it. That is the point that I think you are missing. No issues at high temperature, no issues when off-level. It just works.

Quote:
A lot of people still think that the propane is the gold standard
Can you cite one who has actually lived with both?
Compared with a compressor fridge, propane units are a joke.
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Old 05-17-2018, 02:53 AM   #36
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A compressor frig can have the venting either inside or outside. Most of the conversions from 3 way units, like ours, are vented outside through the original frig vents so no heat inside at all. Even if it were vented inside, as I am sure others who have them vented inside will confirm, they really don't generate much heat at all. Probably less than a 10 watt light bulb.
Our RT compressor reefer is 5 cubic feet and generates so little heat from the inside vent that it's not even noticeable unless you put your hand on the vent.

FWIW, between the boiler and reefer heat exchange, the back area vent space on a 3 way is pretty warm. The escape flu relies on simple convection; lots of original installations don't even have a fan to assist pushing this heated air up the flu and out of the coach. The flu is contained in the sidewall of the coach and IMO it's likely that some of this heat will end up in the coach interior.
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Old 05-17-2018, 03:09 AM   #37
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This is a very interesting thread and I suspect we are all creatures of our experiences and personal viewpoints. Today, I topped off the propane tank for about $20. Our 5 cubic foot three way refrig will soon be crossing the plains of West Texas and Eastern New Mexico. I fully expect temps to be over 100F. Our refrigerator will (as it always has done) keep the freezer around zeroF and the refrig in the high 30s. Being an older (2007) rig, it can be adjusted up and down as to temp. We will be running the refrig on LPG virtually the entire two weeks and we will be boondocking.

I am sure compressor refrigerators are very efficient and wonderful. I am also sure that for our two week trip we will keep our food cold, our hot water heater hot and in the mountains we will probably take off the morning chill with the gas heater. When we get home, we will have (if past experience is a predictor) 2 or 3 gallons left in our 10 gallon equivalent LPG tank.

Life is good. Life in our RT is better than the tent of our younger years. A hot shower every night (thank you, Suburban and LPG) will be welcomed. I want nothing more. It is truly nice to have something that fits our needs. Perhaps we have just been lucky with our three Cs and four Bs over the decades. Never had a refrig problem. Not once. Just luck..............and very complete meticulous maintenance by yours truly.

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Old 05-17-2018, 03:10 AM   #38
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Everyone has an opinion and they largely depend on use.

How do you use your RV? At campgrounds that always have power? Boondocking with no power available? If you always have power then forget propane.

Do you have solar? A large battery bank? A generator? If the answer is no then you need either shore power or propane. If yes then forget propane.

Lots of rough roads? Off roading? a 3 way is probably your answer.

Personally? I always have shore power or a generator, and I wasn't going to spend $1400+ on a fridge that mostly works well if you're in the shade, it's not humid, there's a breeze, you pre-cooled it for 24-48 hours and Saturn is rising. I spent $140 on a fridge that gets cold quick and has more space than I need.

I can buy ten "bar" fridges for the cost of one 3 way fridge. If a fridge only lasts two years then it would take 20 years for that 3 way fridge to finally pay off assuming it did not need repairs in that 20 year time frame.
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Old 05-17-2018, 04:08 AM   #39
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Our RT compressor reefer is 5 cubic feet and generates so little heat from the inside vent that it's not even noticeable unless you put your hand on the vent.

FWIW, between the boiler and reefer heat exchange, the back area vent space on a 3 way is pretty warm. The escape flu relies on simple convection; lots of original installations don't even have a fan to assist pushing this heated air up the flu and out of the coach. The flu is contained in the sidewall of the coach and IMO it's likely that some of this heat will end up in the coach interior.
Tell me about your Roadtrek and the model of refrigerator you have..... what year and model coach....
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Old 05-17-2018, 07:06 AM   #40
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Tell me about your Roadtrek and the model of refrigerator you have..... what year and model coach....
The Roadtrek is a 2017 210 Popular Eco 800ah, 200w solar, GU, VS

The reefer is a 5.5 cu ft Norcold.

On the 210, thru 2015 it was a 3-way unit. In 2016 RT went to a compressor version that operated on 12 volts and 120 Volts. The current version is wired for 12 volts only and is the Norcold model DC558. I have added AcuRite model 00986 digital wireless temp meters (www.AcuRite.com) which tells you the status of the cold and freezer compartments. For their 190 model, they are apparently sticking with a 3-way unit.

A plus for compressor units is that they come down to temp very quickly compared to 3-ways which can easy be as long as 15-18 hours after startup. When running, the compressor is audible but not intrusive. Compared to the roof AC, it's quiet as a mouse. Although it's probably affected by outside temps, the duty cycle I typically experience seems to be in the whereabouts of 30-40%. On my 3-ways I used a small fan in the cold compartment to make the compartment temperature more uniform. That doesn't seem to be necessary with the compressor reefer.

However, since it is a single compressor/single evaporator unit, like your reefer at home, it takes some fiddling with the thermostat to get the optimum temps for both reefer and freeze compartments. I haven't used the reefer in extremely hot environments, but it seems to be pretty indifferent to outside temperatures. The 3-ways I've had seem more sensitive to that.

This model is also used in the the Zions and perhaps other models. Other than some early corrections made in the battery protection setting, I'm not aware of any problems that have emerged regarding this reefer.

My original requirement for cubic size when choosing a coach was 7 cu ft but I was surprised how well the 5.5 ft unit serves us. That said, if I was doing a DIY, I would go for a state of the art Nova-Kool RFU7300 which has dual compressors and evaporators. With this configuration you have totally independent control of the cold and freezer compartments and I wouldn't be surprised if you could shut either one of them off to minimize power used. Coachmen installed this model in their 24FL Galleria and I think it was a smart move.
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