12v “Dan Foss” reefer vs efficient residential reefer

[noteven]

12v Dan Foss fridge vs inverter powered ac fridge - 

which be the better setup for mostly boondocking energy efficiency wise? 

For use in my truck camper. 

Take the $100’s in price difference and spend that on solar and batteries? 

Or buy the fridge designed for efficiency and the shock and abuse in a marine application in the first place? 

[Zulu]

Read about it here

[noteven]

Thanks Zulu 

[JimK]

Read the article cited above.  Note for a danfoss compressor fridge you will need a couple hundred watts of solar or more and batteries with a capacity of a couple hundred AH or more.  You will need way, way more than that to run a standard household fridge.  So much power is needed you need to consider only using the fridge when you have a hook up or a generator running constantly.  You can run one with solar only but you would need a large battery bank and several solar panels.

[Yarome]

1 hour ago, JimK said:

....you will need a couple hundred watts of solar or more and batteries 

Ohhh.. I dunno 'bout that. Properly installed they really don't take a whole lot more juice than an absorption refer so it's not as if solar is "required"... or an exceptionally large battery bank if the one you have now suits your needs with a standard LP fridge.

A residential refer is also quite doable for many with an adequately sized battery bank and method of recharge (be it solar, genset or both). Not "as", but still in use by many a full time boondocker.

There are definite advantages with a 12v compressor type. If your rig comes with a standard absorption type it doesn't make a "whole" lot of sense to replace a perfectly functional refer with a compressor type, but if you're looking for a replacement it's certainly something to seriously consider.

IMO, one of the biggest setbacks, when doing a replacement, is the possible loss of refer capacity in an already "fixed" sized refer opening. For the compressor types to function as intended (low power consumption) requires adequate insulation on all sides (in the neighborhood of 2"'s worth) that can limit what size of refer you'll be able to install. Without proper insulation then the compressor will be running near constantly in even mildly warm temps which is counterproductive when trying to conserve energy in a dry camping/boondocking situation.

I know they really tout those as being safer, especially while under tow, and able to run when severely out of level. #1 is hooey. Non LP is of course "safer", but that doesn't mean that LP "isn't" safe. To me that's kind of like saying keeping your vehicle parked in one spot is safer than driving. Well... yeah... it is, but that doesn't mean driving is especially dangerous if you use a bit of common sense, follow traffic laws and pay attention to what you're doing. The other argument is that you save LP. True, but LP isn't usually the commodity that causes me to make a trip into town. I'll run out of food, water and need to dump my tanks LONG before my LP tanks need refilling.

Severely out of level. Give me a break! The more level the better, but absorption refers will function perfectly fine 6 degrees of level. Have you ever tried to cook on the stove, move about your rig or try and sleep in a rig that is 6 degrees out of level?? It's not in the least bit fun... which is why leveling blocks were invented. 😉 30 degrees out of level is utterly rediculous.

For example: 1 degree is equal to .017 inches per inch. So a 25' rv 6 degrees out of level would mean that the front of your RV is 30 inches higher than the rear. 30 degrees out of level?? In the same RV, one end would be 12.75 FEET higher than the other.

In a boat I could see where a 12v compressor type would be the most logical choice. In an RV... there a pros... for sure. They cool quicker and can maintain cooler temps in higher ambient temps. Fairly inexpensive mods are available for absorption refers if you find cooling to be less than satisfactory, but the compressor type will generally do a better cooling job "out-of-the-box".

If one was offered in my selected rig I would certainly take it. If not it certainly wouldn't deter me from purchasing my chosen rig... and I certainly wouldn't throw out a brand new, perfectly useable absorption refer.

That's just me, though. YMMV

The "main" issue... as I see it is in the installation. Many are inproperly insulated and "appear" to be functioning as it should, but the compressor run time is exponentially longer than an absorption refer and can consume darn near what a residential would.

Do they live up to their claims? Likely. Would the average RV'er ever experience many of the situations a 12v compressor refer would remedy? Not in most folks lifetime.

I'm entitled to my own opinions. 😉

[Kirk W]

 

6 hours ago, Yarome said:

A residential refer is also quite doable for many with an adequately sized battery bank and method of recharge (be it solar, genset or both). Not "as", but still in use by many a full time boondocker.

I suspect that far more RVs today are used in similar fashion to us, in that we rarely spend a night without at least electric connections and with our present RV have never spent more than 2 consecutive nights dry camping. That leaves me wondering why we still see very few smaller RVs with a 120V refrigerator? Aren't the smaller 120V refrigerators also "Energy Star" rated and so energy efficient? In our use, the recharge while towing might need to be increased from typical but little else. I keep watching for some smaller RVs to start to use the apartment refrigerators readily available....

6 hours ago, Yarome said:

Without proper insulation then the compressor will be running near constantly in even mildly warm temps which is counterproductive when trying to conserve energy in a dry camping/boondocking situation.

I have had similar thoughts. While converting to a 120V unit will typically increase the refrigerator capacity, the 12V compressor refrigerators do not have that same benefit but in a conversion are typically smaller if insulated well. Even in an OEM installation, the insulation will either mean more spade used or a smaller refrigerator. 

6 hours ago, Yarome said:

I know they really tout those as being safer, especially while under tow, and able to run when severely out of level. #1 is hooey. Non LP is of course "safer", but that doesn't mean that LP "isn't" safe. To me that's kind of like saying keeping your vehicle parked in one spot is safer than driving.

2

You stated some things that I have said many times. I'll wait to see some real-life success stories first hand before I just into this one too strongly. 

[JimK]

Even a small residential refrigerator is going to pull about 350 watts and usually substantially more.  That means 24 hours of use will pull about 700 AH at 12 volts.  To be able to handle even one day without solar would require 1400 AH of batteries and about 1400 watts or 10 full size solar panels. 

I don't see how anyone could consider that to be doable, unless you have constant hook ups. 

 

[Yarome]

21 hours ago, Kirk Wood said:

I suspect that far more RVs today are used in similar fashion to us, in that we rarely spend a night without at least electric connections....

I have had similar thoughts. While converting to a 120V unit will typically increase the refrigerator capacity, the 12V compressor refrigerators do not have that same benefit but in a conversion are typically smaller if insulated well. Even in an OEM installation, the insulation will either mean more spade used or a smaller refrigerator. 

IMHO,  capability and market share. "Many" are cord dependant. "Many" move from park to park and full hook-ups daily with just the occasional overnight dry dock. 

The perspective here on RVNetwork may be somewhat skewed since many are (or were) full-time/long term retired RV'ers in rigs geared more toward extended use, "corders", and in what the industry would consider "luxury" RV's. Also to consider is that those that are cord dependant tend to "see" only those that are also cord dependant and avid CG'ers.. but doesn't necessarily represent the entire gambit of RV'ers.

Rigs geared more toward the "luxury" market.. Ie., large extended use coaches... is where you'll likely see more emphasis put on all electric.

Alternator charges... even after the expense of dedicated wiring... and without getting into commercial equipment with dedicated alternators... in general, provide a very poor charge. You're generally better off to run your genset for an hour or two upon arrival.

In light of the "average Joe", who may not be all that energy conscientious, If we didn't still have absorption refers then having a good working knowledge of 120v/12v systems, expanded electrical systems and method of recharge would become more of a "requirement" that would overcomplicate use for a guy that just wants to take his family out every now and again for a long holiday weekend with the smallest learning curve and hassle... while still being able to do pretty much everything he can do at home. Let's not forget the sportsmen/women cadre that may only see occassional use of their RV but are more location oriented, which isn't always cord friendly, and longer term dry campers. From your hunters, fisherman, ATV'ers, divers, auto race enthusiasts... etc.

There is no getting around the fact that absorption refers have been, and continue to be, the most electrically efficient when off cord.

If anything, it seems that dry camping enthusiasts are becoming more prolific. We see that reflected in a combination of ever increasing holding tank sizes, solar pre-wiring, and multi true deep-cycle batteries (with a dash of lithiums) becoming more prolific in dealer installs... among others. 

From the industry perspective an AC/LP refer covers all the bases. The cord dependent, the boondocker, and the occassional user that doesn't want to read "the 12v side of life". 😉

"I have had similar thoughts.."

Well said! Unfortunately, this is another area where the RV industry tends to fall flat on their faces... even with OEM installations. Many are installed as simply an absorption refer substitute without consideration to the specific requirements needed by a 12v comp type to peform as intended. If you're having one installed and not the DIY'er type... do yourself a favor and take your rig to a marine shop. 😉

For me, a 12v comp isn't a deal maker or breaker, but it might be for some. "Out-of-the-box", you'll likely get a better "cool" out of a 12v compressor type... if installed correctly... at the expense of a little extra juice... but will also save on your LP. Nothing like a residential, but it's going to cost a "tad" more out of your battery bank. Inproperly installed... it'll break the bank (pun intended). I'll admit that most absorption refers, "out-of-the-box", leave a little to be desired in the cooling department. A little fine tuning of the baffles (first ensuring the installer actually put one in) and a couple of very inexpensive and easy mods can be greatly improve performance. Not everyone wants to futz with their refer though so they live with what they got and are sometimes disappointed with performance and defrosting hassle.

Some of those small apartment type residentials are making their way into the boondocking world. True. As PV prices drop and battery chemistries improve I'm sure we'll see a lot more of em. If you want more refer space, improved cooling characteristics and don't want to pay an arm and a knee cap to install (or repair) an absorption refer then they are a very viable option if you have the electrical to back it up.

It does come at "some" cost though so for me... I choose not to go that route. While I typically have more than enough daily energy production capability to support one, my battery bank only has "so" many AH's of life (3000cl's x 220 usable = 660,000ah life). The slower I spend them the longer my bank will last. I also don't need more refer space than I have and it's modded for performance. I also like keeping my energy reserve high so gen time is minimal and a few days parked in limited sun or poor weather is of no concern.

Some circles are looking for all electrical but there remain many that are perfectly content with 12v and LP.

[Yarome]

8 minutes ago, JimK said:

Even a small residential refrigerator is going to pull about 350 watts...

They don't run continuously ya know. 😉

In moderate climates maybe 10min on the hour and far less overnight.

[JimK]

You are right.  I should not have exaggerated and given a continuous run time calculation.  You are not right about the operating efficiency.  At least not for my refrigerator.  Mine is highly dependent on ambient temps.  For ambient temps in the low 70s, the unit will run about 25 percent of the time if the door is kept closed for about a third of the time for normal use.  Efficiency drops way off with increasing temps.  By the time the ambient reaches the upper 80s to low 90s, my unit runs almost continuously.  It also runs for a long time when any substantial amount of warm items are added.  That is still a huge amount to pull from battery banks and solar panels.

My Nova Kool 4 cuft refrigerator pulls about 35-70 AH per day depending on ambient temperature.  I still need at least one large AGM battery and 1 full solar panel to keep up with that.  I rarely have a hook up and try to avoid running the generator.

[Al F]

1 hour ago, JimK said:

...........................My Nova Kool 4 cuft refrigerator pulls about 35-70 AH per day depending on ambient temperature.  I still need at least one large AGM battery and 1 full solar panel to keep up with that.  I rarely have a hook up and try to avoid running the generator.

Your Nova Kool fridge looks to be about the same size as the DanFoss fridge and is using about the same 60AH a day stated in the link provided at the start of this topic.  Read about it here

JimK, I am not directing these questions to you.

So what is the difference?  Or is the Nova Kool using a DanFoss compressor.

What happens when you move up to a 8 or 12 cu ft fridge with a DanFoss compressor? Are we talking about a 120AH or 180AH a day usage?  Do they even make such a fridge?

One number I have seen, from what I feel is a reliable source, is a 21 cu ft residential fridge taking about 225AH a day.  This is in 42' MH.   That compares very favorably with the DanFoss 4 cu ft fridge if you upgrade it by 5 times to match the 21 cu ft.

 

[JimK]

Nova Kool makes quite a few different refrigerators using Dan foss compressors.  There are actually two sizes of compressors available.  Power consumption and compressor output can also be adjusted by the refrigerator manufacturer.  These units are designed for 12 v operation and are more efficient than typical residential refrigerators.  A residential fridge will also require an inverter with additional loss of efficiency.  Nova Kool has a pretty good website if you are interested. 

 

[Al F]

10 hours ago, JimK said:

Nova Kool makes quite a few different refrigerators using Dan foss compressors.  There are actually two sizes of compressors available.  Power consumption and compressor output can also be adjusted by the refrigerator manufacturer.  These units are designed for 12 v operation and are more efficient than typical residential refrigerators.  A residential fridge will also require an inverter with additional loss of efficiency.  Nova Kool has a pretty good website if you are interested. 

 

Interesting.  Nova Kool has refrigerators up to 9.1 cu ft.  Pulls 5.2amps while the compressor is running.  Hard to determine how many hours a day the compressor will run as that will be based on outside temp and opening/closing of the doors.  It does seem to be pretty efficient though.

If I was doing the install I would add extra installation around the outside of the fridge to help keep the cold inside the fridge.  Of course there needs to be some sort of venting for the compressor area to let the heat escape.

So far I am unable to find a price list.  A couple of distributors I looked at say to call for pricing. 

[JimK]

1 minute ago, Al F said:

Interesting.  Nova Kool has refrigerators up to 9.1 cu ft.  Pulls 5.2amps while the compressor is running.  Hard to determine how many hours a day the compressor will run as that will be based on outside temp and opening/closing of the doors.  It does seem to be pretty efficient though.

If I was doing the install I would add extra installation around the outside of the fridge to help keep the cold inside the fridge.  Of course there needs to be some sort of venting for the compressor area to let the heat escape.

So far I am unable to find a price list.  A couple of distributors I looked at say to call for pricing. 

Again there are two different compressors depending on refrigerator size.  The smaller pulls about 3.5 amps and the larger is about 5 amps.  Figure  run times of about 33 percent for 70 degree temps and near 100 percent for high summer temps.  Power consumption will range from about 30 AH per day to over 100 AH per day for a larger unit running with high ambient temps.  You will also notice high power consumption when cooling room temperature items.  When I add a couple of 6 packs of drinks and some other room temp items, my refrigerator is likely to run continuously for several hours.

I tried the idea of superinsulation.  Of course, you cannot add insulation for the door or the bottom or the back of the unit.  The insulation I added to the top and sides did not seem to do much.  I added a couple of computer fans to move the air on hot days and that makes a noticeable improvement.  The sun beating down on the side of the camper is hard on the power consumption.

[Bill Joyce]

Another brand to look at for efficient 12 volt fridges is Sunfrost, http://www.sunfrost.com/ .  I have seen these in bus conversions.. 

Energy usage and other specs here - http://www.sunfrost.com/efficient_refrigerator_specs.html .

[Al F]

3 hours ago, Bill Joyce said:

Another brand to look at for efficient 12 volt fridges is Sunfrost, http://www.sunfrost.com/ .  I have seen these in bus conversions.. 

Energy usage and other specs here - http://www.sunfrost.com/efficient_refrigerator_specs.html .

Great info.  The website even gives the energy star rating for each fridge.  Makes it easy to compare to a standard household fridge.

[D&J]

I looked into the Danfoss DC compressor a few years ago when I needed a cooling unit for my Domitic LP frig, from my refrigeration days I used some Danfoss equipment and it worked great. First it is not a DC compressor it's a A/C compressor with a custom built inverter attached to the side of the compressor, the variable speed is something that has become common place in the industry and it works for power saving but not all that noticeable in a small unit like that but they are quiet because of the ramped startup just like the variable speed blower motor I have in my air handler at home. They also have a terminal for running a fan motor, I didn't look that close to see if it was AC or DC. What I came up with is the sizes of refrigerator are very small and you can get about the same efficiency by using a small dedicated quality inverter just to handle a small domestic refrigerator. If I was going to install a domestic refrigerator I would install a dedicated inverter not one that runs other appliances, the inverter can be a modified some wave because a AC motor doesn't really care. I run my standard freezer all the time when going down the road and our dorm refrigerator sometimes off our modified inverter and they are happy and the truck keeps the batteries charged.

I installed a new Almish cooling unit in my Domitic frig.

Denny 

[Yarome]

30 minutes ago, D&J said:

First it is not a DC compressor it's a A/C compressor with a custom built inverter attached to the side...

Good to know. I guess they may just "appear" to more energy efficient than regular residential types due to the small size of the refer compartments.

In that case, my thoughts would be revised. A 12v compressor type "would" likely be a negative factor for me when selecting a new rig. Not having ever been presented with a rig with a factory installed Dan Foss I guess I've neglected due-diligence in that area.

Thanks for sharing D&J. 

[D&J]

If I was going the compressor style refrigerator I would go with a residential with a high efficiency rotory style compressor with a dedicated inverter not the piston compressor Danfoss is using. The rotor style compressor have a softer start and are quieter than the old piston ones. Also remember if you use a modified sine way inverter get a good one that's a step wave not a cheap square wave.

Denny

[Al F]

Not to mention the cost of a residential fridge may by 1/2 to 1/3 the cost that I saw on the 12 cu ft SunFrost fridge.

[Jack Mayer]

All these reasons mentioned above is why I have a residential refrigerator and a reasonable size solar and electrical system. In my case, I run it off the main inverter, not a dedicated inverter. I ALWAYS have my inverter on....but it would be slightly more efficient to have the separate inverter. I have enough solar and battery that I don't notice the "inefficiency". 

 

[oldjohnt]

In addition to the regular LP/Electric RV fridge I run a second 120 VAC Compressor Fridge which isn't necessarily one of the latest super energy efficient or specialty units. Its powered by my PSW Inverter and house battery bank being charged usually off solar and/or the truck engines alternator if/when rarely necessary driving, so even if its not as efficient as some models above, it doesn't bother me nor cause any undue or excessive load even when dry camping indefinitely.. HOWEVER I still like having the regular LP Gas/Electric fridge and wouldn't be without one for all the options/choices (LP orrrrrrrrrrr Electric) and convenience it affords IE the best of BOTH worlds.

 To each their own

John T