Chest freezer to digital controller conversion.

TucsonAZ · June 2014

I mentioned this in my other thread but felt starting a new one to put the info out there to people would be nice. I am modifying a chest freezer to run at warmer temperatures (less energy consumption) for my solar project. I can go without many things but a way to cool my food isn't one of them so this is a must have. I don't actually want to use it as a "fridge" as much as I do a really warm freezer (I have it set at 24 degrees right now) but I'm hoping there's enough of a top to bottom temperature variation that I will have some control over how frozen things get.

My initial thought was to keep the stock controller and adjust via the course adjustment screw however after 3 days of trying, I simply couldn't make that fly. That means using a digital unit and the 1w draw that comes along with it, I guess I can live with that and at least know the temp in the freezer at all times.

I went with an MH1210F, this is a face mount digital unit in fahrenheit so that's a plus, it was $14 shipped on Amazon and the instructions are abysmal actually stating:

"The temperature control host machine cannot be installed in the place where is dripping water, the elderly, children could be touched."

That aside, I'm impressed so far so we'll see how it goes, I will keep you posted on the Kill-A-Watt data including adding first with two days of normal use then 2 days of adding a one gallon jug of water each day.

The "host machine" is a GE 5.0cuft unit that isn't energy star certified. I wanted to use a 3.6cuft unit but no time after the first one was damaged in shipping and already had this one.

The install was fairly easy other than having to really clean out the old hole for the temp probe to feed the new one in, the fit was tight for sure but it went in after a little prep work. With a stainless plate over the front, it will look better than new.

There is also the potential if need be to add a 80mm computer case fan to the roof if I'm unhappy with the temps in there being uneven, I would avoid this due to the power usage but I think it could be installed fairly seamlessly if desired.

BB. · June 2014

Re: Chest freezer to digital controller conversion.

Out of curiosity--Why "so warm" of freezer temperature? Food will not keep near as long as when stored at 0F or below...

-Bill

jonr · June 2014

Re: Chest freezer to digital controller conversion.

TucsonAZ wrote: »

I'm hoping there's enough of a top to bottom temperature variation that I will have some control over how frozen things get..

If you want a warmer area, you should be able to create a foam box that sits inside the freezer, is open at the top and seals against the freezer lid. Ie, it gains some heat through the lid but can't lose much to the rest of the freezer.

I'd record ambient temperature too - power use data without it is pretty meaningless.

TucsonAZ · June 2014

Re: Chest freezer to digital controller conversion.

BB. wrote: »

Out of curiosity--Why "so warm" of freezer temperature? Food will not keep near as long as when stored at 0F or below...-Bill

I don't want to deal with any potential issues that come with running a seal box that has no circulating air as a fridge and I want to extend the life of things but not for months like I would at home. This seems like it will be a middle compromise.

I will of course keep in mind that ambient temps, I am guessing they will always be in the 60-90 range but will update on that.

Currently, it has been on for 33 hours and has used 10 watts per hour (0.33kwh total) in a house that has an mean temp of 78 and me opening the top about once per hour while I'm awake. It seems to kick on for about 90 seconds every 10-15 minutes. I have it set to 23 with a 5 degree margin so it turns on at 28 and off at 23 degrees. I was off on the "surge" and when checked with my clamp meter it seemed to be about 14 amps for less than a second.

I will run it like this for another 16 hours then start freezing water every 4-6 hours.

waynefromnscanada · June 2014

Re: Chest freezer to digital controller conversion.

TucsonAZ wrote: »

It seems to kick on for about 90 seconds every 10-15 minutes..

That's way too many starts, up to 144 start surges per 24 hour day! Not good.
I've converted at least 6 freezers to fridge and ran into similar problems. Solved it by gluing the sensor to a metal mass that takes time to change temp. that was much much better, but still to many starts per hour. Finally put the sensor/metal mass assy in a bottle with a tight cap. Wire through a hole in the cap and sealed. That did the trick. Now it runs for 5 minutes once per hour. Each situation will be different, so some trial and error will be required.
BTW, I run my "fridge" very very close to the freezing point and find things last several times longer than they would in a regular fridge. Love it. AND if you want a drink of ice cold whatever - - it IS ice cold!

TucsonAZ · June 2014

Re: Chest freezer to digital controller conversion.

waynefromnscanada wrote: »

That's way too many starts, up to 144 start surges per 24 hour day! Not good.
I've converted at least 6 freezers to fridge and ran into similar problems. Solved it by gluing the sensor to a metal mass that takes time to change temp. that was much much better, but still to many starts per hour. Finally put the sensor/metal mass assy in a bottle with a tight cap. Wire through a hole in the cap and sealed. That did the trick. Now it runs for 5 minutes once per hour. Each situation will be different, so some trial and error will be required.
BTW, I run my "fridge" very very close to the freezing point and find things last several times longer than they would in a regular fridge. Love it. AND if you want a drink of ice cold whatever - - it IS ice cold!

It's a foot deep into the chest freezer temp probe hole (metal tube) which took some effort to make happen, the hole is sealed so I'm thinking it is about as good as I can get it in terms of not having to run a wire into the unit which I would like to avoid (kids using it). I'm sure I could adjust the temp swing so that instead of going on at 28 and off at 23 it would go off at say 20 and on at 28, I'm sure that would help a good deal, right now I'm just kind of experimenting but what you're saying makes sense for sure.

vtmaps · June 2014

Re: Chest freezer to digital controller conversion.

TucsonAZ wrote: »

I'm hoping there's enough of a top to bottom temperature variation that I will have some control over how frozen things get.

Don't count on it.

TucsonAZ wrote: »

I don't want to deal with any potential issues that come with running a seal box that has no circulating air as a fridge and I want to extend the life of things but not for months like I would at home.

Look at the literature for Sunfrost refrigerators... they claim that their very tight construction with no fan keeps food fresher and does not dry out vegetables.

To the extent that you do want freezing temps at the bottom of your conversion... do you expect to keep frozen food? If so, it will not be a good freezer at those warm temps. Have you considered using it as a freezer, making ice every day, and using the ice to keep your food cold in a cooler?

--vtMaps

TucsonAZ · June 2014

Re: Chest freezer to digital controller conversion.

vtmaps wrote: »

Look at the literature for Sunfrost refrigerators... they claim that their very tight construction with no fan keeps food fresher and does not dry out vegetables.

To the extent that you do want freezing temps at the bottom of your conversion... do you expect to keep frozen food? If so, it will not be a good freezer at those warm temps. Have you considered using it as a freezer, making ice every day, and using the ice to keep your food cold in a cooler?--vtMaps

At this point I'm more concerned with power consumption than anything else, adjusting the temps is as simple as dialing it in with the press of a button. I'm not keeping anything in it that won't be used, eaten and gone within a week so I'm feeling like high 20s will do a good job of that without having to take forever to thaw things out. I guess time will tell how this works out but I'm thinking I will be fine and make the adjustments as I go, I may go up a few degrees as well after seeing how it goes.

notes · June 2014

Re: Chest freezer to digital controller conversion.

Maybe this will help. Use the pressure chart for the temperature and refrigerant you are using. Then convert pressure to temperature on p/t chart. This should get you close and lesson the amount of short cycling. Also very important as to mounting thermostat bulb to evaporator coil. Needs to be surface mounted in, as in contact with coil. Also should be on the last few passes of coil.
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TucsonAZ · June 2014

Re: Chest freezer to digital controller conversion.

For a quick update, I put just a touch over a gallon of water inside the chest freezer and after 48 hours I'm at 0.75 kw (most of which was in the first 24 hours) which is much higher than the other testing. The water still hasn't frozen either so it's not like you're going to be freezing a gallon jug and freezing it a few times a day and getting the high level of energy efficiency.

My thought at this point is to maybe get 4-5 bags of frozen ice, put that inside and see what that does in terms of energy use. That would allow me to have ice and a place to store it without any issues or worry of it thawing.

Not perfect but a work in progress for sure.

BB. · June 2014

Re: Chest freezer to digital controller conversion.

TucsonAZ wrote: »

48 hours I'm at 0.75 kw (most of which was in the first 24 hours) which is much higher than the other testing.

I guess you probably meant 0.75 kWH of energy.

Making ice is quite an energy draw... It will cause any refrigerator/freezer power consumption to go up quite a bit. Add a fan to move air around the ice bucket (when the pump is running), and your energy usage will be even higher (until the ice freezes sooner--then back to normal).

If your freezer runs at 25%-50% duty cycle in normal operation--Depending on how much "warm food" and water you put in the unit--You could see your power usage go up by 2-4x during the "freezing"/cooling of the new product to remove that latent heat.

-Bill

Chest freezer to digital controller conversion.

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