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Old 06-04-2021, 02:08 PM   #1
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Fridge

Back again with another question for y'all. I'm trying to budget out my build a little bit, and right now I'm trying to figure out a fridge. I don't want one of the box ones, I want the typical free standing fridge with freezer ontop and fridge on bottom with the side open doors. Im looking for one that runs on 12v and is roughly apartment size, definetly not full size but not a mini fridge. (if you know of any in a vintage style, you get extra points) I'm not trying to break the bank on a fridge though. So if you know of any decently priced(or cheap bc it has one dent in it from transit, ect type deal) that also has good energy effiency I'd be greatful.

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Old 06-04-2021, 02:17 PM   #2
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Your cheapest option would be to get a traditional apartment style or mini style fridge and run it on a small inverter. Will cut the price in half at minimum. Otherwise, a larger traditional RV fridge.
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Old 06-04-2021, 03:44 PM   #3
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I hear you don't want a chest refrigerator, yet they are much more efficient. Packing them allows you to put more in a smaller amount of space, and when you open the top all the cold air stays in the bottom.

That said, if you want a regular, say 7cuft refer/freezer, I agree that a standard 110v run off an inverter will give you the biggest bang for your buck.

I haven't seen many 12v stand alone, most of them are a combination of 110v/12v or 12v/propane or all three. Any combination is much more expensive.

I'm still batting around what I'm going to do. Ug.
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Old 06-04-2021, 11:31 PM   #4
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Do you you guys think a fridge would run on a standard (square wave) inverter? I have a 400 watt unit I was going to use for on the road A/C power (crock pot, ice maker..)
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Old 06-04-2021, 11:59 PM   #5
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Fridge

It will probably run on a square wave (“modified sine wave”...) but it’s not ideal, for two reasons.

Fridge compressors use split phase capacitor start motors, and the capacitor heats up and wears out much, much faster (easily 10x if not 100x) because of the fast rising edges of the signal.

Secondarily, the generated heat needs to be pumped out, and therefore the fridge consumes more power.

It is true that the chest types are MUCH more efficient. If you’re seriously budget constrained, get an efficient chest freezer off Craigslist for $30 or $50 and hack it to run at 37 degrees.

400 watt is not enough.

Get a new 1500W or 2000W pure sine wave inverter instead of the fifties style fridge. I mean, you do what you want, but if I had $200 to spend, that’s what I would do.
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Old 06-05-2021, 03:27 AM   #6
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I'm not really on a budget but I was curious about the little inverter. I'll just run the fridge off of my main inverter, whatever size I find that I need. Thanks for the info
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Old 06-05-2021, 08:19 AM   #7
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I have a used chest freezer with a thermostat gadget to keep it around 37°F and it's insanely efficient, drawing an average of 16 watts on AC (although the instantaneous draw while the compressor is running is higher and on startup higher still, so it would not be as efficient running off an inverter on batteries). Air has a low thermal mass compared to the solids and liquids inside, so I think the efficiency is more due to thicker insulation and better door seal on the chest freezer than to the fact that it opens from the top.
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Old 06-07-2021, 01:24 AM   #8
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Originally Posted by musigenesis View Post
I have a used chest freezer with a thermostat gadget to keep it around 37°F and it's insanely efficient, drawing an average of 16 watts on AC (although the instantaneous draw while the compressor is running is higher and on startup higher still, so it would not be as efficient running off an inverter on batteries). Air has a low thermal mass compared to the solids and liquids inside, so I think the efficiency is more due to thicker insulation and better door seal on the chest freezer than to the fact that it opens from the top.
What is the thermostat gadget to keep it at 37 degrees??
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Old 06-07-2021, 04:34 AM   #9
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What is the thermostat gadget to keep it at 37 degrees??
https://www.amazon.com/gp/product/B0002EAL58/

That price, though! It was $50 when I got it. I think there are cheaper varieties than this out there.

Like, I think this one would work although I'm not sure: https://www.amazon.com/dp/B07KC24CKD/. Chicks dig it!
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Old 06-12-2021, 03:44 PM   #10
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Chest Fridge

My 3 cu ft chest freezer runs fine using a 210 watt solar panel and three Walmart batteries feeding a 2000w sine wave inverter. I use this: Inkbird ITC-308 temp controller. We have a 4 window E350, so it fits perfectly. For a bigger bus, maybe two chest freezers would work, one for fridge and one for freezer?
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Old 06-12-2021, 03:55 PM   #11
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You should read my Custom Fridge thread..the newer inverter compressors can run from a $20 inverter, as they do slow start with 3-phase motor, not induction motor, so no high surge that needs an expensive and sin wave inverter. So not particularly important to run on 12v directly when a $20 inverter gets the job done. These compressor are only used in the full sized fridges that are very expensive when new.

If you are anywhere near sascramento, I have a small fridge I picked up on the side of the road that didn't have a compressor or anything, and could put in an inverter compressor for you. You can read my thread and see how to do it yourself.

The other thing I will note I have said often, is that the value of a top freezer not spilling out the cold when you open the door is actually not that important if you need to cool your bus, as it let's cold air in the bus. The problem is the compressor creates heat that IS in the bus. So you are best to put the compressor and condensor radiator OUTSIDE the bus, and then there really isn't an issue spilling cold into the bus from the fridge unless you are in the cold trying to stay warm.
The chest freezer and many mini-fridges embed the condensor in the walls of the fridge to radiate the heat there, so can't do the outside setup, and also requires the fridge have sufficient air space around it, which tends to be a problem in small tiny houses.

Another issue is the chest freezer and the mini-fridges have no defrost, which requires you defrost them manually.. which entails emptying the entire fridge, warming it up, etc, not very convenient for full-time living.
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Old 06-12-2021, 07:19 PM   #12
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Originally Posted by elkoskoolie View Post
My 3 cu ft chest freezer runs fine using a 210 watt solar panel and three Walmart batteries feeding a 2000w sine wave inverter. I use this: Inkbird ITC-308 temp controller. We have a 4 window E350, so it fits perfectly. For a bigger bus, maybe two chest freezers would work, one for fridge and one for freezer?
That's what I'm doing. I have a 4.5 cu ft upright chest freezer that I'm using as a fridge, and a 1.1 cu ft chest freezer that I'm using as an actual freezer. I have a 1.1 cu ft dorm refrigerator in my house that I really wanted to re-wire and use as a freezer (for the symmetry of it all) but I couldn't figure out how to do it.
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Old 06-12-2021, 07:21 PM   #13
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Another issue is the chest freezer and the mini-fridges have no defrost, which requires you defrost them manually.. which entails emptying the entire fridge, warming it up, etc, not very convenient for full-time living.
A chest freezer kept at 37°F doesn't need defrosting (unless I'm missing something here).
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Old 06-12-2021, 08:05 PM   #14
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Originally Posted by BeNimble View Post
You should read my Custom Fridge thread..the newer inverter compressors can run from a $20 inverter, as they do slow start with 3-phase motor, not induction motor, so no high surge that needs an expensive and sin wave inverter. So not particularly important to run on 12v directly when a $20 inverter gets the job done. These compressor are only used in the full sized fridges that are very expensive when new.

If you are anywhere near sascramento, I have a small fridge I picked up on the side of the road that didn't have a compressor or anything, and could put in an inverter compressor for you. You can read my thread and see how to do it yourself.

The other thing I will note I have said often, is that the value of a top freezer not spilling out the cold when you open the door is actually not that important if you need to cool your bus, as it let's cold air in the bus. The problem is the compressor creates heat that IS in the bus. So you are best to put the compressor and condensor radiator OUTSIDE the bus, and then there really isn't an issue spilling cold into the bus from the fridge unless you are in the cold trying to stay warm.
The chest freezer and many mini-fridges embed the condensor in the walls of the fridge to radiate the heat there, so can't do the outside setup, and also requires the fridge have sufficient air space around it, which tends to be a problem in small tiny houses.

Another issue is the chest freezer and the mini-fridges have no defrost, which requires you defrost them manually.. which entails emptying the entire fridge, warming it up, etc, not very convenient for full-time living.
Do you know if I can install a inverter compressor in my RV fridge that runs on propane or 12 volts? Are inverter compressors available in 12/24 volt or only 110 volts? Thanks
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Old 06-12-2021, 08:17 PM   #15
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Originally Posted by musigenesis View Post
A chest freezer kept at 37°F doesn't need defrosting (unless I'm missing something here).
The coils frost over pretty much at any temp if the fridge is working.
The more they have frost the less efficient they work.
A normal fridge runs a defrost cycle like every 1 or 2 hours.

I can see they might 'defrost' after it reaching temp and sits a while at 34F,
might work better at 38F or 40F, you want your beer at 40F right?
This would create water that would build up at the bottom.
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Old 06-12-2021, 08:20 PM   #16
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Do you know if I can install a inverter compressor in my RV fridge that runs on propane or 12 volts? Are inverter compressors available in 12/24 volt or only 110 volts? Thanks
The propane fridges work differently. They would need a different evaporator in addition to removing all the ammonia plumbing. Could be done I'd guess.
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Old 06-12-2021, 10:44 PM   #17
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The propane fridges work differently. They would need a different evaporator in addition to removing all the ammonia plumbing. Could be done I'd guess.
I found a fridge conversion video and a website for JC Refrigeration who sell conversion kits. They do not say anything about the compressor being inverter technology however. Do you know where to buy a kit with inverter compressor?
https://youtu.be/Yte1V3CkDrw
https://jc-refrigeration.com/
I am not associated with either link.
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Old 06-12-2021, 11:43 PM   #18
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I found a fridge conversion video and a website for JC Refrigeration who sell conversion kits. They do not say anything about the compressor being inverter technology however. Do you know where to buy a kit with inverter compressor?
https://youtu.be/Yte1V3CkDrw
https://jc-refrigeration.com/
I am not associated with either link.
Great video, showed all the details. I've watched some of their other ones, good channel.

Still no defrost. I think they may make them this way to keep the ammonia and its fire danger isolated from inside the fridge.

I would hack into the box and put a regular evaporator with the defrost that drains to the outside. But no 'kit' is going to work for that, or it would be lots more work and probably not look professional..

The good news is the heat from the condenser gets vented to the outside. You could not put a mini-fridge with condenser coils on the fridge walls in that space, it would need the condenser setup like the kit.

While those wood panels are nice, I'd balk at the $800+ cost of the kit and find another way.

I don't know of any kits with inverter compressors, surprised they don't offer one, but it would add a lot to the cost using new components, as I recall the replacement inverter compressors for the big fridges are like $600 vs $200.
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Old 06-13-2021, 04:58 AM   #19
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Quote:
Originally Posted by BeNimble View Post
The coils frost over pretty much at any temp if the fridge is working.
The more they have frost the less efficient they work.
A normal fridge runs a defrost cycle like every 1 or 2 hours.

I can see they might 'defrost' after it reaching temp and sits a while at 34F,
might work better at 38F or 40F, you want your beer at 40F right?
This would create water that would build up at the bottom.
I'll have to keep an eye on this. I ran mine as a fridge in my garage for a year and I didn't noticed any decrease in efficiency (it stayed around 16 watts no matter what). My guess would be the compressor doesn't run long enough for a huge amount of frost to build up on the coils and then it sits long enough for that to melt in between cycles. I did notice a small bit of water on the garage floor, which makes me realize I need to have some sort of drip pan with drainage underneath the thing when I use it in the bus (which I haven't yet).
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Old 06-13-2021, 08:07 AM   #20
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Sundanzer makes a 12v fridge freezer combo. Not cheap but super efficient. I bought their smallest freezer and am using a refrigerator thermostat. https://sundanzer.com/product-category/household/

Great info in this thread.

Originally Posted by elkoskoolie View Post
My 3 cu ft chest freezer runs fine using a 210 watt solar panel and three Walmart batteries feeding a 2000w sine wave inverter. I use this: Inkbird ITC-308 temp controller. We have a 4 window E350, so it fits perfectly. For a bigger bus, maybe two chest freezers would work, one for fridge and one for freezer?
That's what I'm doing. I have a 4.5 cu ft upright chest freezer that I'm using as a fridge, and a 1.1 cu ft chest freezer that I'm using as an actual freezer. I have a 1.1 cu ft dorm refrigerator in my house that I really wanted to re-wire and use as a freezer (for the symmetry of it all) but I couldn't figure out how to do it.
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Genius.

I was considering dropping serious coin on an Engle freezer. Love this site.
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