Using a Chest Freezer as a Refrigerator

[Farmhand]

Hi all, Ok so we know that when we open the door of an upright fridge we let the cold out the bottom and the hot in the top. So why not convert a chest freezer which opens at the top to be a fridge. So when we open the lid the cold stays inside. I think it save's energy.

I'm not a fridge mechanic so i don't know if it is OK to just add a thermostat to control the temperature of the chest freezer to acheive this. But I did do it. And it works as a freezer or a fridge with digital control. I can set the temp and the amount it rises before coming on again (the fluctuation). Say if I have fresh chickens to chill I can set it to 2 or 3 degrees C for 24-48 hours to chill and rest them (just over freezing point), then after the rest period I adjust the temp to -18 C and deep freeze them. Make's em yummy.

It cost about $60.00. to convert but the converting hardware will likely outlast the freezer. I haven't used it for about a year but I'm going to set it up in the bunkhouse when I rearrange it soon.

I've almost forgotten how to actually wire it up and lost the instructions for the digital thermostat thingy. But it is easy to do with an external plug-in thermostat and fix the probe inside. When I wrestle it out of the corner I'll get some picture's.

Any thoughts on this and the difference between a fridge compressor and so forth as compared to a freezer one and if this would save energy? I don't really have the wattmetering ability to tell conclusvely. Most of the time opening the top to get something out then put it back in doesn't make it turn on from loosing it's cool.

Cheers

[wrtner]

It would be interesting to put a variable resistor in series with
the thermostat's sensor. This may simply alter its range of operation.

[theremart]

Conversion.

Hi,

This has been done on a yahoo group converting to a standard fridge. As well some on youtube have used them as chicken incubators using a small heating pad for a lizard with a tempreture control.

[dutchdivco]

Been done

10 years and 3 computers ago, i read about doing this. I believe the guy that posted on it was in Australia, but not sure. He told how he did it, and calculated the amount of savings, and it was phenominal, in comparison to using a standard upright refrigerator.
I 'favorited' the site at the time, but of coarse don't have it anymore. I'll try to look for it, and post it if i find it.Jim

[dutchdivco]

Yepp,

Google "Chest freezer as refrigerator", and you will see numerous 'hits' about this; concensus seems to be the compressor runs about 2 minutes per hour, or it uses 0.1kw of electricity. It give you a tremendous savings over the standup type refirgerator.;-) Jim

[Farmhand]

Hi guy's, It works by the digital thermostat reads the temp inside with probe the normal plug from the freezer plus into a socket which connects to the thermostat and power. This way the standard thermostat still works but I turn it to coldest and the temp is controlled by the digital thermostat, so I can use it at pretty much any temperature I want from it's coldest about -18 C up to fridge temp 3 or 4 degrees C or more I guess. The digital thermostat allows control of the differential meaning the temperature it allows the fridge to rise to before it turns on again to cool it back down.

The big difference to a fridge and why I did it is because the top opens and not the side. If the air is still the cold all stays in there like water in a cup.

Also leaving the freezer intact it can still be used normally as before just by unplugging the digital controller. It's not that practical for a lot of things like a regular fridge but it is good for things that are needed often or special temperature requirements.

I'm not saying anyone should do this or anything, I did it mainly so I could run it as a fridge from an inverter. But also to go from chill to freeze when full. Basically just allows a higher maximum temp and more control.

This is the little Digital thermostat I used and a relay behind it although the unit has an internal one anyway.


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These are the probe's.


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Cheers

[Farmhand]

10 years and 3 computers ago, i read about doing this. I believe the guy that posted on it was in Australia, but not sure. He told how he did it, and calculated the amount of savings, and it was phenominal, in comparison to using a standard upright refrigerator.
I 'favorited' the site at the time, but of coarse don't have it anymore. I'll try to look for it, and post it if i find it.Jim

Oh well that sounds good, I could tell it was saving me money and it very useful too. I got the idea from the internet too but most were actually rewireing the freezer. This way is easy, but it should be wired by a qualified person if connected to the grid. I think.

I guess I could measure it's current and voltage when on and then time the on time but that sounds like a lot of trouble.

I think I'll just use it.

[Farmhand]

Hi,

This has been done on a yahoo group converting to a standard fridge. As well some on youtube have used them as chicken incubators using a small heating pad for a lizard with a tempreture control.

Yeah me too.

Here's one of the incubators I made.


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And here's a chicken I prepared earlier.


Uploaded with ImageShack.us

I retired the incubator though, the chickens do the hatching now.

[mbrownn]

Some things are best left to nature

I use a chest freezer to make a chiller for my bacon production. when set to its lowest setting it is -5C but half way between that position and off it is at about 5C, perfect for wet cure bacon. I have to watch it though because vibration sometimes causes the switch to the off or minimum setting. Even though it is double the power of my ref, it uses less power at this because the insulation is better and the cold air is not all lost when i open it.

[Farmhand]

Yeah it important to cure the meats. Makes a huge difference, some monkeys around here think, just kill em and eat em then they say the tough meat is the fault of the meat. That's like blaming the pencil for a spelling mistake. Can't tell em though they keep trying to tell me chilling is just to make things easier to cut up, which it does, but the number one reason is rigor and chemistry. Even with fish.

I guess it's relevent, food is renewable energy stored in matter.

[dutchdivco]

Farmhand

I like your approach; not needing to re-wire the freeser, and being able to easily switch from fridge to freeser and back; a definite improvement on the original concept!
Also like the idea of being able to run it off of an inverter; is it because it uses such a small amount of electricity that your able to do so? And, what 'size' or wattage of inverter are you using. If you don't open it, how often and for how long does the compressor run? And, if you open it for 1 minute, and close it, how long does the compressor run.That would probably give a pretty good idea of how much energy its using.

The one disadvantage of this is its a little more aquward to get into and out of, and get stuff, than a regular fridge.I'm thinking some shelves, that slide from side to side, near the top, or even several layers of shelves.
Basically, divide the width by 3, and make 2 shelves for each layer, so their is always an open area to get to the layer underneath. Actually, drawers would be more accurate, rather than shelves, as they would need sides to hold everything in.
Also, raising it up off the floor some, so the bottom wouldn't be as difficult to reach? Jim

[Farmhand]

Hi dutchdivco, You're right the drawback is the inconvenience of accessing things in there. But as you say it could be modified depending on you're needs and the freezer size. With shelves and stuff.

I'm in the middle of a rearrangement just now. But I will get some numbers as soon as I can for the on time after opening. The off time before starting again does depend a bit on the temp and the amount of stuff inside (thermal mass) but from memory it can sit for quite some time without coming on, if I don't open it I think over an hour. But I will confirm those times as soon as I can. I'll set up something to rattle when it comes on, to alert me.

And get a current/voltage reading. It runs from 220 but I'll measure it when it's on anyway. I'll also check out exactly how I wired it, some temp controllers are heating controllers some are cooling controllers, some both. I think that might be why I used the extra relay. To reverse the switch state. I'll check it out.

The inverter I use is a 1000/2000 watt sine wave inverter. I'm not sure if a sine wave inverter is necessary though. Thats just what I have. It uses almost an amp in standby. Which is a bit rough.

I also need to enclose the controller and clean up the wiring, I meant to clean up the wiring last year but I got sidetracked by free energy. The wiring can wait.

I should have some numbers tomorrow.

Cheers

Oh yeah, if I want a longer off time I just set a bigger differential, but that means a bigger temperature fluctuation and more overshoot/undershoot.

.

[Core]

.....Any thoughts on this and the difference between a fridge compressor and so forth as compared to a freezer one and if this would save energy? I don't really have the wattmetering ability to tell conclusvely. Most of the time opening the top to get something out then put it back in doesn't make it turn on from loosing it's cool.

Cheers

By all means if you have something to tinker with......tinker away! Truth is all the internet talk is just wrong. There is no savings, actually it may even cost more to operate.

Let me address the quote above first. On the residential end there is really not much of a difference on compressors. The same compressor that does the refrigerator does the freezer. So the compressor serves a dual purpose. Each manufacturer does change the way they provide refrigeration to there boxes. As an example some will use one coil for both sides and cycle each fan on T-stat other units may have two coils, one containing a refrigerant valve to control evaporator pressure.

Regardless on the residential end there is really only one type of compressor used in a side by side refrigerator/freezer. These compressors also are typically refrigerant 134a. It should be made clear also that a typical refrigerator/freezer (side by side) have evaporator fans to circulate air.

Chest freezers are completely different. The chest freezer are modeled after the old 'meat lockers'. These units had gravity coils meaning, no fan on the evaporator. They were just coils hanging over your head in a warehouse keeping the food refrigerated. Back in the old days the entire ceiling would be covered with coils. I can tell you from experience that trying to find a refrigerant leak on these systems was brutally difficult and very time consuming.

A real chest freezer has 'no' evaporator fan, The coil is behind the plastic wall and stuffed with insulation. (Side note: I have seen a units called chest freezers that have a fan and coil set-up like a typical upright freezer. These ARE NOT chest freezers)
Anyway you can see already that with a solid barrier between the coil and product heat transfer is retarded as oppose to a fan circulating air over a coil. Note, the better quality chest freezers have a stainless steel interior and not plastic.

The job of a chest freezer is simply to build ice inside the unit. Ice growth is typically 2-4 inches and this is normal. The refrigerant does not cool air directly in these units, it job is to keep ice growth happening. A true ice chest does not have a typical t-stat reading air temperature they operate off a refrigerant pressure control. What should be understood clearly about refrigeration systems is when the temperature of the box goes up the refrigeration pressure goes up. If refrigeration pressure goes up amps go up. Also in a hermetic compressor it is the refrigerant that cools the electrical windings. So a compressor running a higher then normal pressure (ie. warmer box) draws more current then a compressor running at design set point. A compressor running outside its design set points (ie. refrigerant pressures running higher then normal) receives less cool refrigerant to cool the electrical windings and will eventually burn out.

Chest freezer just freeze ice only. These compressors usually use a different refrigerant. In the old days it was R-502 now it can vary maybe R-404a or other alternative. Because these units serve only one job, to freeze, unlike there counterparts the reach in refrigerator/freezer these compressors are engineered for that one purpose. I am sure everyone will agree that operating any motor in a manner it is not designed for can not be very efficient. Basically you are over heating the motor by not letting it work in an environment it was designed for meaning the compressor is always running under a heavy load.

A real chest freezer cost more to operate as a refrigerator then your refrigerator/freezer combo. Most people do not go in/out of there converted chest freezer as often as there refrigerator. And to boot chest freezers are generally kept in basements or other area's were the ambient air is cooler or fairly constant. Your refrigerator is in your kitchen and the condenser coil is subjected to warmer air.

As far as air goes, its insignificant. Air has a very low specific heat and the amount of time you keep your door open plays almost no role. This of course assumes you don't leave your door open for 10 minutes. A chest cooler generally has more insulation then your standard refrigerator. This is because real estate in a refrigerator is prime. Also the refrigerator has to fit in your kitchen and must be made to generally agreed to standard sizes.


None of what I said is meant to discourage anyone from tinkering, have fun! But the truth is that a real chest freezer with a compressor operating outside its design parameters will never be more efficient then a system of like size operating at design conditions.

BTW- Its the small motors in refrigerators/freezers that are the real energy hogs. These motors are about 60% efficient at best. As is the case with all A/C motors the smaller the HP the less efficient they are. A chest cooler has no fan motors hence less current is used.

BTW2- A chest cooler takes some time to build ice and get to its operating point. At times its best to place a pot of water inside to accelerate ice production. But once at operating point it is not uncommon for the compressor to be off for days at a time.

-Core

[Farmhand]

Hi Core, Thanks for the detailed reply. I appreciate it. I'll definately keep those things in mind. I should have some numbers in a few hours.

My main thinking originally was the convenience of going from refrigerate to freeze while still full for chilling meat then freezing it. Then I noticed it came on a lot less than my regular upright fridge (no freezer) even if I left the lid up. So I started to use it as a fridge. When I do I use it I am opening it up all day long like i do with the normal fridge. Except with the lid on top very little cold escapes as compared to a upright fridge which just spills out a lot of cold and kicks in almost immediately.

I guess it is dependant on use, convenience and if you have a discarded chest freezer to use, that you got for free.

I don't have a basement, it is very hot everywhere here in summer no air con. Also being able to controll the differential, I can cntroll the temp it coms on and goes off. I can make it ten degrees difference if I want, or 0.1 degrees C i think. Of course the less the differential the moreoften it will come on and the closer it will stay to the set point (less overshoot).

If I'm chilling or freezing, I don't open it and I usually keep lots of water in there. Down in the very bottom can be frozen but near the top not.

I'm of the opinion it is saving me money. I'll find out compared to the small fridge I also use when I'm not using the "freezge".

Thanks for the good info. I very much appreciate the reply. It does make sense. So I will not ignore it.

Cheers

[Farmhand]

Hi all, The freege uses about 180 watts when it comes on at 4.2 degree's C but that quickly drops to about 110 watts. From a 12 volt battery with the 800 Ma from the inverter added thats 15 amps dropping to 9 amps. Clamp Meter's not the best but close. There is not much inside it so maybe it would work better when it's full. Anyway.

I have it set to come on at 4.2 Degree's C and the differential is set to 1.2 Degree's C. It stays on for close to 2 minutes, and is off for 25 minutes. After shutting off at 3 degree's C it overshoots down to 1 degree C, probably because it is so empty (only about 10 litres of liquids in it).

I opened it like normal got something out then put it back after a minute, but that didn't do anything conclusive, it seemed to make no difference. So I just opened the top and left it open.

With the top open it stayed on for a fraction longer and was off for nearly 3 minutes less.

So over a 24 hours how it is, it would be on for about 2 hours which is a bit more than I thought. I'll check it again in a few days, when it's been full for a while. That would be about 25 or 26 Ah from the battery per day. Maybe a bit more. Not much but still I thought it would be less.

Cheers