Using a 120 vac Dorm Fridge

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fraz627

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Has/Is anyone out there used a dorm Fridge, was thinking of a 4.3 CF magic chef Fridge/Freezer. I plan of having 400 amps of battery.
Looking at the user manual,  It states that it shouldn't be box in, and not to be run of an invertor.
Any comments or suggestions.
 
Some people here do use household fridges. Typically speaking those who do have loads of solar panels. An alpicool 12v compressor fridge for instance can use (depending on region tropical, mountainous, etc) around 60 watt hours over the course of 1 day. A dorm fridge often uses that many watt hours in 1 hour or less.
 
I've been using a dorm fridge for years. 150ah of available battery capacity, 180watts of solar, could only run it for 2-4 days depending on solar conditions. It's very inefficient. You can lose up to 20% energy through the inverter going from 12v to 120v. Usually by the time you bought enough batteries and solar panels to run the 120v fridge effectively, you could have easily had the money to buy the more efficient 12v fridge with a smaller battery bank and solar array. I just installed a 12v fridge in my new rig, have yet to fully test it out. Yes, like all fridges, the little 120v dorm fridge needs airflow and has to be vented. But running off the inverter will not hurt it. They are usually tough little units. Keep in mind that if you're running 400ah worth of lead acid or agm batteries, you only have 200ah of usable power as per the safe 50% rule. Lithiums can go to 90%.
 
Some people claim they work well for them. I can't say that, for me the one I tried didn't work well at all. sucked way to much power to keep food safe.

Invertors can run from 70-90% efficient, most inverters run all the time. Meaning they are using power while just sitting there doing nothing.

The price of 12v refrigerators has come way down. I just don't see the advantage. Back when I tried to use a dorm fridge, 12v refrigerators were way expensive.

One last parting thought. back in 2009 I wanted to get off ice, it was way to expensive. I tried everything, a peltier cooler, a 3 way RV fridge, a dorm fridge, I would even seal up and bury an ice chest to make the ice last longer. I will tell you right now I would be dollars ahead if I would have just bought a 12v fridge. in my case trying to avoid spending the money on a 12v actually cost me money.

I now have three 12v refrigerators. I use 1 as a freezer and 2 as refrigerators.

Highdesertranger
 
I added a bunch of insulation inside the fridge resulting in a very small cold space.  There is no coil on the back.  The entire outside steel box is used to dissipate the heat.  That is good to reduce condensation, a problem in high humidity Florida.  The daily energy use is low because of the added insulation.  The initial testing before adding the insulation led me to believe that it would be marginal with two 100 watt panels and I only have one. 

It can be done but, in my opinion, it is not worth the time and effort.  You can get a tiny Iceco or Alpicool for about $200 or less.  The dorm fridge with added insulation, electronic thermostat to control the inverter, testing, experimenting, takes a lot of effort, time, engineering, and money.  Back when a 12 volt fridge was $600 - $1000 it made sense.  Today, not so much.

I posted a thread about my fridge:
https://vanlivingforum.com/showthread.php?tid=27624
 
Simply put, it works for me just fine. I run it on two Trojan GC2 batteries on a 2000 watt inverter. Efficient? not as it could be but then again it works and it was a dirt cheap investment. Already had batteries and inverter so $69.00 for the fridge and I'm good. I can put almost a weeks worth of food in it, including 8 frozen meals in the freezer section.
 
MikeRuth said:
including 8 frozen meals in the freezer section.
That as I see it is the only real advantage of a dorm fridge. They're cheaper, yes. But then you'd need a pure sine wave inverter. Over a hundred bucks for an inverter, 70 to 100 bucks for a dorm fridge. You're at or above the price point for a 12v compressor fridge at that point. More efficient as no inverter losses, can be used as a freezer, and easily manageable in most climates with only 100 watts of solar. 

But dual zone 12v fridges cost more. So you lose out on a freezer AND fridge. I plan to buy 2. 1 freezer, 1 as a fridge. Still lower than most dual zone units and if one dies I still have another to store food until I can replace it.
 
Another thought. Idk what type of refrigerant the 12v fridges use but the last fridge I bought had a huge warning label.

CAUTION! CONTAINS FLAMMABLE REFRIGERANT!

Just something to consider. Maybe the 12v fridges also use the same refrigerant. I don't remember seeing any fire warnings on auto air conditioner refrigerant bottles you get at the auto parts stores, but maybe all refrigerant gasses are flammable.
 
highdesertranger said:
 . . . The price of 12v refrigerators has come way down.  I just don't see the advantage.  Back when I tried to use a dorm fridge,  12v refrigerators were way expensive . . .

XERTYX said:
 . . . But then you'd need a pure sine wave inverter. Over a hundred bucks for an inverter, 70 to 100 bucks for a dorm fridge. You're at or above the price point for a 12v compressor fridge at that point . . .

Please tell me where I can get an upright 12 V, 2.3 cu.ft. refrigerator for under $200 (that is what I have in my fridge and inverter).
I just looked and quality upright 12V fridges are going for ~$900 (Dometic, Isotherm, Norcold, Nova Kool, Vetrifrigo).
 
highdesertranger said:
Some people claim they work well for them. 

{snip}

The price of 12v refrigerators has come way down.  I just don't see the advantage. 


The advantage for some is that they already own either the dorm fridge or the inverter. 

The advantage for others is the front opening or the very quiet, fanless operation of most dorm fridges.

Another advantage is the nearly 100% reliability of the dorm fridge simple mechanical thermostat, and long life of the typical dorm fridge, and if it does crap out, it's about $100 or maybe less for a whole new fridge, versus the high replacement cost for a new 12v fridge or its electronic control board. Replacement parts might be un-available in 5 years.

Another advantage is the fact that the inverter can be used to power other items in the van or camper. I also have used both, and both solutions worked well for me.

If you are buying everything brand new and cost is no object, AND you have room for a chest type fridge, then the high quality 12v dual zone units like the Engel, Whynter, Dometic or Luna are the way to go. You can spend just under $1000 and get a nice front-opening 12v truck fridge (Indel-B) type or Novacool, but a fairly complex installation is required and you know, they are kinda pricey!

But a simple countertop dorm fridge/inverter combo is not a bad way to go, especially if the inverter you use is one that has an automatic (and energy saving) 'sleep' or 'standby' function.
 
Spaceman Spiff said:
Please tell me where I can get an upright 12 V, 2.3 cu.ft. refrigerator for under $200 (that is what I have in my fridge and inverter).
I just looked and quality upright 12V fridges are going for ~$900 (Dometic, Isotherm, Norcold, Nova Kool, Vetrifrigo).
Touché, but I can tell you where to get a reliable 0.7 cu ft 12v upright fridge for under $200

https://www.amazon.com/dp/B075R1LH8D
 
Go for it. I have bought and sold good dorm fridges on craigslist for around $50. If you want to give it a try then get hoppin and don't worry so much about what other people think.Your plan has woked fr some and not for others. If it does not work out for you then you can resell the fridge on craigslist and replace it with a 12v unit.

I bought my used Engle for $300. I was gifted a larger 45 quart Waeco which is now known as Dometic but it was too big for my space and needs so I sold it and that funded the Engle which was just the right size.

A used dorm fridge will be the perfect start. The inverter is also something you can find as used equipment as people are upgrading theirs quite often. You might even get gifted one or the other fridge or inverter from someone in the community at van build gatherings.

Someone on the local facebook market in Quartzsit recently sold a large used Engle that was imported and relabeled as a Norcold for $250.

As to how much energy a friddge uses, that depends on the ambient air temperatures. But the dorm fridges or large household fridges do not run as efficiently when it gets really cold. They are designed to be used at 60 degrees or warmer, because that is normal household temperature range. I learned that when I was doing a remodel in the winter and had my new fridge positioned in an unfinshed, unheated room. I could not undrstand why it was not keeping the food cold so had a repairman come out to fix it. The fridge was fine, it was the room temperature that caused it not to work.
 
That's really interesting that they don't work as well in the cold. I have a dorm fridge on my family property that has power but no water. The room where the fridge is isn't climate controlled and in the winter it does seem to not work as well. The freezer compartment always ices over and in the winter it seems to thaw some and drip water from the freezer.

The main reason I prefer the 12v units over the household ones other than the small footprint is that they sip power. If I were in a full sized RV with a kilowatt of solar on the roof I would likely go with a household unit. Same reason people don't normally use 12v units in their house. They have access to nearly unlimited cheap electricity.

If space and price were no object I'd say go with a sundazer 12v unit. They're as large as a deep freezer but have about as much room inside as a dorm fridge. The rest is hefty insulation.
 
XERTYX said:
That as I see it is the only real advantage of a dorm fridge. They're cheaper, yes. But then you'd need a pure sine wave inverter. Over a hundred bucks for an inverter, 70 to 100 bucks for a dorm fridge. You're at or above the price point for a 12v compressor fridge at that point. More efficient as no inverter losses, can be used as a freezer, and easily manageable in most climates with only 100 watts of solar. 

But dual zone 12v fridges cost more. So you lose out on a freezer AND fridge. I plan to buy 2. 1 freezer, 1 as a fridge. Still lower than most dual zone units and if one dies I still have another to store food until I can replace it.

NOPE, mine runs just fine on a MSW inverter. Just an FYI. 
 
Last year I converted a 5 x 8 cargo trailer for my BIL who was homeless. I mounted a 250 watt solar panel on the roof, put 2 - 1 year old never discharged 95 amp hr AGM's under the bed powering a 750 watt Harbor Freight modified sine inverter. All the inverter powers is a 1.7 cu.ft. dorm fridge. The 12v system also powers 2 - 6 watt led fixtures and a usb charging port. He he has run the fridge for a solid year on this system with no issues what so ever. He can get 3 days of 24/7 fridge power with no solar recharge. I put in a 120v system to power a 700 watt microwave, 5000 btu window unit and 10 amp battery charger for the times he has access to shore power. Ideal? No. Does it work and is it reliable for him? Yes

BTW - The fridge draws 10 watts during it's duty cycle - 15 min/hr in 85 degree outdoor temps. My Iceco Go20 12v fridge draws 35 watts during it's duty cycle - 25 min/hr in 75 degree indoor temps.
 
That's interesting that you say it doesn't work as good when it gets cold as I had the complete opposite experience. Mine had trouble when it got hot. It ran almost 100% of the time and still wouldn't keep food at a safe temp. Highdesertranger
 
tx2sturgis said:
The advantage for some is that they already own either the dorm fridge or the inverter. 

The advantage for others is the front opening or the very quiet, fanless operation of most dorm fridges.

Another advantage is the nearly 100% reliability of the dorm fridge simple mechanical thermostat, and long life of the typical dorm fridge, and if it does crap out, it's about $100 or maybe less for a whole new fridge, versus the high replacement cost for a new 12v fridge or its electronic control board. Replacement parts might be un-available in 5 years.

Another advantage is the fact that the inverter can be used to power other items in the van or camper. I also have used both, and both solutions worked well for me.

If you are buying everything brand new and cost is no object, AND you have room for a chest type fridge, then the high quality 12v dual zone units like the Engel, Whynter, Dometic or Luna are the way to go. You can spend just under $1000 and get a nice front-opening 12v truck fridge (Indel-B) type or Novacool, but a fairly complex installation is required and you know, they are kinda pricey!

But a simple countertop dorm fridge/inverter combo is not a bad way to go, especially if the inverter you use is one that has an automatic (and energy saving) 'sleep' or 'standby' function.


These are the issues I had. In addition, I don’t have 12V outside the cockpit. I don’t trust myself with electrical upgrades, so adding outlets is an added expense.

I have a rare class B with quality, solid wood cabinets I don’t want to tear down. There is no fixed place for a chest fridge, except on the tub, and the limit there is 23x29. Otherwise, I’d have to move it up and down the aisle to access the kitchen, bathroom, and cockpit. I did consider a large Dometic on wheels for that reason. But I already have mobility issues, I don’t need to add another obstacle.

There isn’t enough depth where the propane fridge was removed. I’d have to buy an expensive compressor fridge to fit there. Instead, I spent $115 for a counter height dorm fridge — using the styrofoam it came in to pad it — and spent the difference on a lithium battery. I may add a second under the hood. I considered removing the microwave and the shelf it was on to fit a 6 cubic ft model with separate freezer, but why complicate things?

I just turned on the dorm fridge Monday and my battery only went down 10% in the 12 hours of darkness overnight (6pm - 6 am). I even forgot to turn the fridge down from the max setting before I left the van the night before.

I’ve also bought an upright Wynter counter height freezer with a similar footprint. That can go on the tub with a board and bungee, with room to spare. I may have an uncle demo the tub and build storage to maximize that space (to hold as Yeti and add general storage). The only way a 12V would fit without wasting vertical space is if we put sturdy slide out rails, so we could pull it out over the toilet.

Granted, I’ve overspent on electrical. But I’ll also use that for other needs — appliances, induction cooktop, heat, and charging devices. I removed my propane tank, as it was 30 years old and rusty. I decided not to replace it, as I’m not comfortable with propane and also plan to urban boondock, with propane banned in tunnels into the city.

I’ve brought this up before, but most Skoolie builds I see seem to have dorm or full-sized household fridges. I guess it’s due to having more rooftop real estate, room for batteries, and often larger budget.


ETA: if my dorm fridge dies, I can replace it for $100 the same day at Target, Walmart, Best Buy, Sams, Costco...
 
sub2rainEN said:
ETA: if my dorm fridge dies, I can replace it for $100 the same day at Target, Walmart, Best Buy, Sams, Costco...

If you buy it at Costco definitely get the extended warranty, then replacement will cost nothing for approx 3-5 years. Many other places also.
 
I've used two dorm fridges in a trailer.  First one, a 2 cu.ft. freebie, then a 40 dollar Craigslist 4.3 cu. ft., powered by two 6v golf cart batteries. Both have a 120vac amp draw of about .5 amp, or about 60 watts.  That equates to a little over a 5 amp 12dc battery draw using an inverter.

Both were run with a Harbor Freight 750 watt modified sine wave inverter.  Smaller wattage inverters would sometimes trip due to excessive starting/inrush current. I used what I already had. Pure sine wave would be a plus.

To avoid the always present battery drain an inverter uses when always switched on whether outputting 120vac or not, I rewired the refrigerator and added two wires to the inverter on/off switch.

The fridges have a standalone two-terminal temperature switch.  One side is connected to the hot/narrow blade of the 120v incoming cord, and the other connector of the temperature switch goes to the compressor.  They used .250" flat terminal connectors from the factory. Removing both wires from the temperature switch and connecting those two wires together causes the fridge to run continuously without turning off.

Connecting a 120vac cord from the inverter to the fridge cord means the fridge runs only when the inverter on/off switch is turned on.  I installed two small wires on each side of the inverter on/off switch.

Connecting those two wires to each side of the fridge's original, now unused temperature terminals turns the inverter on and off as the temperature switch closes and opens.  Expecting the inverter to turn on and also provide starting current simultaneously seems to be the reason for a higher rated inverter.

It's worked for five years, and has been bounced around quite a bit. Finding a dorm fridge with the coils in the back instead of the skin would be a plus for insulating while also getting rid of heat.
 
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