DIY Chest Fridge - Automatic Timer Relay

The existing thermostat is a factory product which tailor-made to the freezer, it is hard to find another which match the freezer with different temperature adjustment.

If modifying the freezer, the warranty woukd be lost!

The warranty probably isn't worth a crap anyway. Any modification will void it.

No reason to make it complicated..............aren't we just talking about a thermostat and an on/off switch.

If the damned thing can maintain freezing, refrigeration should be a piece of cake.

If putting a temperature probe inside, the wire may obstruct the door closing. Furthermore, put such a device inside may also obstruct the storage of food.

GA

Thats the answer.

i've considered doing this myself. i never have enough room to store my beer. the change-over is fairly simple. replace your existing thermostat with one from a refrigerator. they cost approx. $30.00 for a new on line. they're all basically the same. try to buy one with a long themocoupler "the aluminum tubing leading from the thermostat". this will give you more mounting options.

1- disconnect the wire running to the "starter". it's a small black box attached to the side of the compressor. it will be marked "start". it should be the center wire of the three.

2- connect the wire you removed to one side of your new thermostat. you might need to lenghten the wire.

3- connect a wire to the other side of the thermostat and run it back to the "start" terminal. your appliance should start and run at this point.

4- the end of thermocoupler should be located near the top of your unit for an accuarate reading. avoid placing it near the evaporator coils. 'the frost lines that appear when the unit is running" i'ld advise taping or gluing it in place.

5- mount the dial portion outside the unit where it does'nt interfere with the opening and closing the unit and away from heat sources.

i hope the information a gave you is correct. if not, i'm sure someone one this site will correct me. there are normally schedmatics located on the back of the unit or hidden near the compressor. you can find them on line if they're not supplied by the manufacturer.

good luck

If you make modification of your freezer in future, please make photo record to share with us!

Thanks

will do

Home brewers have been doing this for years. Try searching Google and Ebay for a "Johnson Controls thermostat" as it will do the job with minimal modifications. There are older analog mechanical "bulb" and newer digital electronic types which can also be found at many home brewing supply stores.

Below is one example of the newer digital A419 model already modified (with US 120Vac in/out connections) for you to make a chest freezer into a chest refrigerator.

example thermostat

sweet

Although I do not agree with converting a chest freezer to a refrigerator, the Johnson A419 temp controller is the way to go.

It is totally programmable including an anti short cycle time period. I can be bought bare bones from your local HVAC supplier.

The reasons not to convert a freezer to a cooler are:

1: when it runs, it wants to freeze down to a certain temperature, anything near the walls of the inside may freeze before the temperature is reached.

2: what do you do with the condensate that will result from the frost melting of the walls of the inside? Some freezers have drain plugs. If so than this will have to be trapped some how, to prevent moist air entering to compartment.

How often have you had someone ask you to solve a technical problem, and when you do, they then add some totally trivial reason that it can't work. Do you suspect you're being toyed with? A thermostat bulb on a capillary tube is the size of a small caterpillar descending the side of the freezer on a rope the size of a pencil lead.

How often have you had someone ask you to solve a technical problem, and when you do, they then add some totally trivial reason that it can't work

Seems like nearly everyday :D

Where do you live, that refregerators are not available?

I am now in Ukraine

check out this guy.

http://www.builditsolar.com/Projects/Conservation/chest_fridge.pdf

I think Tornado was the first with a respectable answer.

An old fridge will have everything you need in it, just strip it out and check that it works before installing.

The home made beer fraternity in the UK build fridges out of chest freezers and this is quite a normal thing to buy/build. The electronic magazine EPE from the UK has a project exactly for that this month.

Commonly available programmable timers for pumps and stuff like that. Not sure what you have locally, but look at Grainger website or other similar.

http://www.grainger.com

Joe

How is the solution i posted of topic ? Using a timer to control when the freezer comes on and off and manually checking the settings until the time is correct is pretty much what was requested in the post. The solution works in the real world we use it currently to regulate old fridges and freezers when the thermostats go in them. Granted it doesnt involve unnecessary and complicated rewiring and fitting of temperature sensors, maybe thats where the solution gets the off topics it hasnt been through a vigourous and expensive re-engineering process and quality audit it just works .

Why the timer idea is unsuitable has been explained both earlier and later in the thread. Please learn about control theory and techniques.

The solution i posted "WORKS IN THE REAL WORLD" Regardless of other posts and solutions given to the problem, it is a cheap solution that does WORK, the statement the timer idea is unsuitable is incorrect.

That is potentially the most lethally incompetent advice I have ever heard. It is a recipe for alternate freezing/thawing of the fridge contents, which will degrade food texture; or, worse yet, for spoilage and food poisoning.

Very well put!!

Which is why the other idiots here (not an engineer amongst them!) who like that method, are probably not long for this earth!!!

Please do not slag the non engineers.

I am one of them. I am just a guy with 34 years in the trade.

If you read my post you will note that I disagreed with the conversion.

Freezers are freezers and refrigerators are refrigerators for a reason.

They were engineered that way.

But most combo units have only one compressor and only the refrigerator side has the temperature control. The freezer side just keeps getting colder until the refrigerator side tell the compressor unit to shut off.

As far as being different compressor designs I have doubts on that as well. I have scrapped out enough of each of them to know many refrigerators and freezers from the same brands share the same compressor systems. Its only the thermostats insulation and evaporator coil layout that are different between a refrigerator and a freezer unit.

I say a old freezer can make a fine refrigerator if the thermostat is switched out and there is away to drain the inevitable condensation buildup out of it.

As far as short cycling goes all refrigerators and freezers have built in protection for that just in case of power blinks that do happen while they are running so no additional timers are required for a modification. You may even get Lucky and find the original freezer thermostat is simple one that uses a screw that changes the force on a spring. those can easily be modified to work at a higher temperature setting just by getting the set screw past its initial travel stops and moving it or out a turn or two.

Just HAD to give you a GA for a fine, well thought out intelligent Engineering post.

That actually not only was fully correct, but also gave an intelligent possible way to fix such a problem....at a very low cost!!

Thanks.

Thanks but unfortunately I too do not have that official pieces of paper that says

'I is an engineer too'.

I guess I could print myself one though but as far as I am concerned that would still.... Um, well........ Isn't that just what colleges just do now anyway?

The compression ratios are different for a refrigerator compressor and that of a freezer compressor.

Other than the thermostat, the refrigerant metering device is set differently for a freezer than a refrigerator.

It is the evaporator pressure that determines the refrigerant boiling rate, therefore the temperature of the freezer coils.

This is a result of the compressor compression ratio, the refrigerant used and the metering device (usually a capillary tube for domestic models).

Combo units just use controlled bleed air from the freezer section, to cool the refrigerator section.

Not in my fridge its doesn't. It has coils at the top of the refrigerator which are an extension of the ones that go around the whole freezer section and it does not bleed air down from the freezer to to its job.

I suggest you read up on phase change heat pump design some more. I have worked with enough various designs to know what does what and how its done to know what you say is likely not true or of very limited application. Typically they are just like any home central air compressor system. If a thermostat does not shut them off and they have enough insulation in the space they are cooling they too can freeze things solid right down to the limits of what ever refrigerant they use is capable of. I have serviced compressors for commercial freezers and for home air conditioners and at the same operating temperatures they have the same high side and low side pressures.

If a refrigerator took cold air out of the freezer section it would have to be replaced by more air and that air can only come from two sources. The refrigerator compartment or outside the unit itself. In either case the freezer section would rapidly collect and condense any moisture present and quickly fill any air passages with a solid block of ice. Just like the old ones did years ago that had the little freezer compartment right in the refrigerator itself. They always needed to be defrosted and deiced every few weeks or anything in the freezer compartment would become in its own iceberg.

I know for a fact that any refrigerator design thats worth a dam will also freeze itself solid if the thermostat is bypassed I have seen it happen before.

You can argue that there are other designs as well and I know that. I just don't feel like writing a text book to explain how every common commercial design works that uses any form of variable expansion valves or other stage regulation type devices. Refrigerators and freezers are mass produced and tend to keep everything as basic as possible to keep production costs down which means most use the same base components regardless of what final purpose they are intended for by the manufacture.

That fits in perfectly with my less than complete fridge knowledge.

GA for that!!

"what and how its done to know what you say is likely not true or of very limited application"

Now there is an insult!

I have worked on designed, corrected and repaired refrigeration systems from my own beer cooler,too drive in freezer storage warehouses, grocery store refrigeration racks, as will as cryogenic cascade systems. It is apparent that you do not have a true frost free refrigerator.

What you described for your refrigerator is a freezer section, that then feeds a evaporator plate in the refrigeration section. The thermostat has a fixed cut in order to allow the refrigerator evaporator plate to thaw on the off cycle.

Have even worked on a modern frost free refrigerator? If so than it is quite obvious that the air from the freezer section is feed to the refrigerator section than returns to the freezer section.

Unless you are working with R-22 only ,even you would have noticed that cooling applications have different pressures than air conditioning.

The one thing that I can agree with is that a bad thermostat can let a unit totally freeze up. Ignored than the superheat gets to low and the compressor will likely be damaged

Where my experience comes from is the American based refrigeration systems where R-22 its the most common used refrigerant here at least has been for more decades than I have been alive anyhow. I have rarely ever seen any American refrigeration or air conditioning systems that where not based on using R-22 that where more than 10 or so years old except for the old ammonia based systems which I don't work on.

the dealers claim all these new refrigerants are so much better but so far I see far too many systems having problems with them than not. It may not be the different refrigerants fault but the negative changes in design and craftsmanship certainly don't help its cause.

As far as the new home refrigerators and freezers go very few of them are worth trying to fix if they do have a problem. Toss it and buy a new one is typically a far better solution. I have a old 1970's unit that was apparently built to last. It may be a crappy lime green color but it still does its job well which is why I don't have a new frost free one that dies every 5 years or less like most people have around here.

We can agree on some things.

As for the new bottom end refrigerators made in China, they are not worth the service call.

As for domestic refrigeration; I have seen sulfur dioxide, ammonia and methyl chloride used.

An accident at Dupont led to the development of CFC's

They have served us well to date, except for that ozone depletion thing.

Where I am from all domestic refrigerators and some commercial units and automotive Ac's used to used R-12. Today it is 134a.

As for AC, the trend is towards R-410a, yet it may be banned by the European Union, as it's Global warming potential is off the scale.

Now R-407c is being pushed for AC, as it is very close in properties to R-22, unfortunately it requires a synthetic oil that is very hygroscopic.

They are shipping equipment based on R-22 that is now phased out and using POE oil and R-407c, to Europe and other areas.

Where this ends I do not know.

Hey tcm,

Been reading along this thread on and off. First I have to agree.......I've never seen a household refrigerator/freezer unit that has more than one compressor.

Second, don't throw out those broken refrigerators, they make great smokers........just put a single burner hotplate on the bottom, followed by a pan of wood chips of your choice. Excellent for smoking fish, turkey, ham, making beef jerky, etc. They make an excellent addition to the yard decor also.

Since my high school days about 20 years ago I have played with propane as an alternative refrigerant. Its T/P curve is almost identical to within a percent or two of R-22 in normal operating conditions.

The de scented and purified form is R-290 refrigerant which has a GWP rating of 3 while every other common refrigerant has GWP rating typically in the hundreds to multi thousands levels.

http://www.navitron.org.uk/page_ref.php?id=83

Unfortunately I don't see much of the AC service industry pushing for a R-290 change out though. That stuff can be made and sold for under $1 a pound while every other refrigerant pushes 10 times or more on the resale end. Basically its too cheap, too easy to produce, too environmentally friendly, and too versatile to be of value to the AC service industry.

It is argued that R-290 is flammable but as someone who has seen it countless times first hand while scrapping AC systems the normal refrigerants tend to atomize the oil in the system when they are vented under high pressure and will most certainly make a very effective flame thrower if ignited!

Seen what happens when the terminal block on a compressor lets go. Yes it is like a flame thrower. Scared the living hell of several customers.

R-290 is a great refrigerant. Unfortunately, like ammonia it has it's problems. It is that whole toxicity and flammability thing.

I use R-290 (cyclo propane) as a oil; sweeping agent for ultra low temp cascade systems.

Some manufactures out there have used propane as part of a mix that is supposed to be a drop in replacement for R-12 in automobiles.

I do not see

A major leak has lead to several under the hood fires.

I do not see propane or ammonia in residential applications. That is why CFC's were adopted.

The good point is that you are not "obviously", "not an engineer".....Compliment (I think that says what I wanted to say!!)

Some here are so obviously nothing to do with engineering or science......guess who? No prizes!!! Its just too damn easy.......

You are obviously not an engineer of any shade or type, or you would have understood the other excellent posts telling you what the drawbacks are........

Its the most stupid answer I have seen for a long time on CR4......using a timer to keep a fridge at the correct temperature....

The only correct way to go is with some form of temperature sensing to make sure that the temperature is held though hot or cold weather correctly.

What you may also not have considered, is the effect on some foodstuffs of incorrect temperature, it can then give you a painful tummy, or even Diarrhoea or worse.

Food must be kept at a correct and constant temperature.....any fool understands that, well almost any......

As Andys ditty says it only takes 6 months to become one heaven forbid someone has a different solution to the gurus and anonamous guests. Because guess what it still works and has been working well through summer and winter for a number of years and thats the point isnt it it works. No one has been sick from it etc etc etc etc the end

Just because you can do a thing does not make it a good idea

you would have us believe that using a timer & fooling around with the on/off cycles, until you get it to work under one set of conditions, is somehow superior to using a thermostat?

now you want to whine because several members [including me] don't agree?

this isn't personal, it's technical. From a technical standpoint your solution doesn't warrant a good answer & is something you might do out of desperation, until you could acquire a thermostat

get over it

No i dont want to whine but i dont want to be castigated and flogged by pretentious gits either. Was it the best solution NO does it work YES. Check out the original question of why the answer was off topic, you dont have to agree with it you can think i am a wanker i dont care but some of you really are full of yourselves it was a simple question of why was it off topic that still hasnt been answered because some of you are to busy trying to make yourselfs feel superior and bully other people if thats what being an engineer is are thank god i am not one of them.

If you don't want to whine, then STOP WHINING!

Bad Solution = Off Topic

if you don't like the format take it up with admin

Some people are just plain lucky. I wonder how long it will last? Do you take bets?

Now if the timer keeps the temperature actually well below the right temperature for keeping food fresh, (which is about the only way to not get food poisoning occasionally) then all you are doing is wasting electricity, not very green.........nor is it good for the pocket book either.

Every "°C" too low really increases electricity usage completely unnecessarily....

Using a timer for keeping a temperature is rather like:-

...driving on the wrong side of the road is ONLY dangerous if a car comes from the opposite direction with a driver who follows the road rules correctly?

So who is wrong? The Guy on the wrong side of the road that had happily driven for miles like that. Or the idiot(?) driving in other opposite direction following all the road rules correctly......?

This is not really a trick question, but it might be difficult to understand and answer for some people.......

Also did you know that eating food that has not been cooled correctly can make you Grouchy?

I recently saw an ad for a mains driven thermostat, with a remote sensor with a flat cable to allow it to be placed in the freezer.....I know its in German, but the picture is fairly explanatory in itself:-

The Link

Nikolay posted on post 16 is a good explanation of why it's a good idea a general outline of how to

The author suggests using the defrost drain for inserting the temp probe

Should I still need to built a relay circuit for this thermostat?

No, you just plug the unit in the wall socket, the temp sensor in the freezer and plug the freezer into the socket you see there.....then you select the temperature you wish to have.....

Using a timer to control a temperature is completely false by the way........even if you manage to get a steady temperature, which I doubt, every time you open it, the temp goes up and if you don't open it for long periods, it will go down.....a temp sensor is the only way to go....

If I read the specs right for the thermostat shown, it can switch 16a at 230v, so a relay would not be necessary. The key concept is that the thermostat contacts are sufficient to handle the compressor current. I'm pretty sure there are plenty of suitable 'stats on the market at economical cost.

You need to use a timer device called as a 'Cyclic Timer'. In this device, the timer has independently settable ON time and OFF time. As soon as you make the timer ON, it goes into cyclic mode. The closed contact of the timer remains closed (i.e. the feezer will be ON) for the preset ON time. After the lapse of the ON time, the contact opens (i.e.the freezer will be off) and will remain OFF for the preset OFF time of the timer.This will continue as long as the electric supply to the timer is On. You can adjust the ON time and/or OFF time over the entire range to get the desired result.The time range of the timer should be selected to suit your process requirement.

Priyadarshan

A cyclic timer can be used for temperature control by controlling the ON time of a heater in case of heating control and ON time of a compressor in case of a cooling control. The only draw back is that the timer setting must be set by trial and error and the temperature accuracy is not very fine. A simple cyclic timer called as simmerstat can be used for this purpose. A thermostat is definitely the best solution but a simmerstat will also server the purpose. The user has a choice.I have used both successfully for different applications.

Priyadarshan

I think zero degree Celsus is a good temperature for trial & error.

Change of state happened in this stage, a lot of energy is required to drop one degree Celsus theorectically.

So I think the temperature should be varied between +3 to -0.5 degree Celsus practically.

It is quite easy to de-frozen food if -0.5 degree Celsus.

GA

It's all about "scare du jour." People are squawking because of isobutane being introduced as a CFC/HCFC substitute in European fridges.

I have made a copy of the article I mentioned for the DIY thermostat, but I have forgotten who wanted a copy, please send me a normal email address via CR4 email and I will mail the .pdf to you....anyone.

The temperature can be set between 2°C (35.6°F) and 19°C (66.2°F).

The only negative part I see is that the mains lamp in most fridges (if using this thermostat to replace a damaged original, but they are not usually fitted to freezers!) will only switch on if it happens to be "ON" at that point in time. An extra circuit with door open switch should be fairly easy to make/fit if required (or keep a flashlight handy!!)