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-   -   AC_Hacker's Hasty Freezer Conversion (https://ecorenovator.org/forum/showthread.php?t=2995)

AC_Hacker 05-02-13 09:38 AM

AC_Hacker's Hasty Freezer Conversion Reduces Energy Use By 61%
 
7 Attachment(s)
There has been talk in a thread in the Appliances and Gadgets section about State of the Art Refrigerators.

I have heard of the legendary performance of converted chest freezers and have been tempted to try one myself. The idea of reaching down into a chest of food has been a bit of a deterrent, also the knowledge that any flat surface in my kitchen will collect things... things like motors, and mail I don't want to read yet, and yard tool, the list goes on... But to clear all that stuff off to get at some food is really what stopped me.

My current refrigerator is a tiny 3 cubic foot freezer/refrigerator which does hold most of what I actually need and also has an admirably small energy foot print. But the freezer is absolutely useless, so the actual refrigerated storage is in the neighborhood of 2.5 cubic feet... pretty small even for me.

I looked for 'all refrigerators' to replace it with and saw several candidates, but their energy consumption was 2x to 3x higher than the one I have. So I started looking for a small vertical freezer to convert.



I saw several, the most attractive was a Haier ($291) with 4.8 cubic foot of space (707 watt-hr/day),



...and the least attractive was a Summit freezer ($350) with about 5 cubic foot of space (879 watt-hr/day).

The photo of the Summit doesn't show it, but the insulation is much thinner than on the Haier... not so thick, not so good.

A quick search through CraigsList turned up the energy hog (non Energy Star) Summit for $125. Being the tightwad that I am, I went for it just to see what kind of a refrigerator a crappy compact freezer would make.



I ordered a digital thermostat from ebay for about $16, free shipping... but then remembered that it might be a month before it arrives...

So I found a spare Arduino-clone 'Teensy++' and a LM355 analog temperature sensor and a Solid State Relay (AKA: 'SSR') laying about and set to work making a bare-bones thermostat while I wait for the unit from China to arrive.



Here's a photo of the Teensy Thermostat. The LM355 is visible at the back of the protoboard between the Teensy and the SSR.



Here's a photo of the hasty test setup, showing the expert use of red duct tape to secure everything.



This is a graph of the Summit performance (watt-hr/day) over a 24 hour period prior to the Thermostat. The yellow line indicates the EPA power use figure, converted to 879 watt-hr/day.



This is a graph of the Summit performance for a period of about 16 hours after the thermostat is being used. The spike is because I put a pot of warm soup into the refrigerator. The average energy use is about 340 watt-hr/day after the conversion. Not a miracle, but quite respectable, and it is a 61% reduction from the energy use of the unconverted freezer.

A refrigerator that uses only 340 watt-hr/day deserves more than casual consideration.



This is a page from my notebook where I wrote about various refrigerators that were being discussed. It is very satisfying that this miserable freezer, once converted (See Red Line In Photo) is able to out perform the $1900 German miracle Refrigerator, and for only $150, too!

[EDIT: A quick calculation suggests that if the Haier freezer had been converted instead of the wretched Summit, the energy use would be about 274 watt-hr/day, and that's before defeating auto-defrost.]

Best,

-AC

See Code Below:

(Of interest is that a 'smoothing' routine has been used to reduce false triggering of the compressor.)

Code:

/*
 * refrigerator_thermostat_smoothed.pde
 * -----------------
 * Sensor (LM335) input is converted
 * to Kelvin degrees, then to Fahrenheit.
 * When temperature exceeds the SetPointTemp, compressor goes on.
 * When temperature is below than SetPointTemp, compressor goes off.
 * Refrigerator temperature is changed by changing SetPointTemp value
 */
 
const int numReadings = 20;

int readings[numReadings];      // the readings from the analog input
int index = 0;                  // the index of the current reading
int total = 0;                  // the running total
int average = 0;                // the average
int inputPin = 38;              // Teensy++ input pin
 
const int CompressorPin =  7;      // Define Teensy++ output pin
const int SetPointTemp =  38;      // Temperature set-point (different value = different temperature)
const int TempVariance = 2;
float temp_in_kelvin=0, temp_in_fahrenheit=0;

void setup()
{
// set the analog pin as input:
  pinMode(inputPin, INPUT); 
// set the digital pin as output:
  pinMode(CompressorPin, OUTPUT);
 
// initialize serial communication with computer:
  Serial.begin(9600);                 
  // initialize all the readings to 0:
  for (int thisReading = 0; thisReading < numReadings; thisReading++)
    readings[thisReading] = 0;         

// Variables will change:
  int CompressorPin = LOW;      // Set initial state. Teensy HIGH turns off the SSR
}

void loop()
{
  // subtract the last reading:
  total= total - readings[index];       
  // read from the sensor: 
  readings[index] = analogRead(inputPin);
  // add the reading to the total:
  total= total + readings[index];     
  // advance to the next position in the array: 
  index = index + 1;                   

  // if we're at the end of the array...
  if (index >= numReadings)             
    // ...wrap around to the beginning:
    index = 0;                         

  // calculate the average:
  average = total / numReadings;       
  // send it to the computer as ASCII digits
  //Serial.println(average); 
  delay(1);        // delay in between reads for stability 

  //Reads the input and convert to Kelvin degrees
  temp_in_kelvin = average * 0.004882812 * 100;
 
  //Convert Kelvin to Fahrenheit
  temp_in_fahrenheit = (temp_in_kelvin * 9 / 5) - 459.67;
         
  //Print the temperature in Fahrenheit to the serial port
  Serial.print("Fahrenheit: ");
  Serial.println(temp_in_fahrenheit);
  Serial.println();
 
 
  // if the temp_in_fahrenheit is >= SetPointTemp,++ turn on compressor and vice-versa:
  if (temp_in_fahrenheit >= SetPointTemp)
  digitalWrite(CompressorPin, HIGH);  // turn the Compressor on (Teensy HIGH turns on the SSR)
  else
  if (temp_in_fahrenheit <= SetPointTemp - TempVariance)
  digitalWrite(CompressorPin, LOW);  // turn the Compressor off (Teensy LOW turns off the SSR) 
  else
  //digitalWrite(CompressorPin, LOW);    // turn the Compressor off (Teensy LOW turns off the SSR)

  delay(1000);                          //wait one sec

}


AC_Hacker 05-02-13 12:10 PM

Continuing to Monitor Performance...
 
Everything is still working well.

The temperature of the refrigerator has been running a bit too cold, so I am tweaking the value of "SetPointTemp" upward to achieve close to an actual 38 degree F inside reading.

All of my digital 'wonder-thermometers' are producing different results, so I am using my fall back lab-grade mercury column thermometer as a standard.

After the first tweak, the temperature went from sub 30 degrees F (difficult to read a mercury column at night) up to 35 degrees F.

I just adjusted SetPointTemp up two more degrees, which should get me to 37 F which would be good enough.

The LM355 was not calibrated, so the temperatures it indicates are not reflective of actual temps. Therefore, the mercury column thermometer is being used as a standard.

-AC

creeky 05-02-13 12:16 PM

Nice. I'm heading to Kijiji now (Candian Craigs list)

Of course the miracle fridge is 12 cuft and has a freezer ...

stevehull 05-02-13 12:27 PM

I guess I don't understand. You are using the EPA estimate as the prior standard? I would suggest running the unit as is, without the modified thermostat, and NOT using the EPA estimate. Then you have a true baseline allowing an apples to apples comparison.

It could be that the new thermostat is better - but why? The insulation is the same, the compressor is the same - what is different?

Steve

AC_Hacker 05-02-13 02:29 PM

Quote:

Originally Posted by stevehull (Post 29732)
I guess I don't understand. You are using the EPA estimate as the prior standard? I would suggest running the unit as is, without the modified thermostat, and NOT using the EPA estimate. Then you have a true baseline allowing an apples to apples comparison.

SH,

I supplied two graphs, the first one was used as a baseline. The yellow bar indicated to me that the asymptote would fall pretty close to the EPA number. That was close enough for me. There is a reason that I used 'hasty' in the title.

If you'd like greater certainty, please try the experiment yourself. That's the way science works.

Quote:

Originally Posted by stevehull (Post 29732)
It could be that the new thermostat is better - but why? The insulation is the same, the compressor is the same - what is different?

The difference is that I'm not demanding the unit to chill the box down to 0 degrees F, I'm only asking it to go to 38 degrees F.

It all has to do with Carnot's Efficiency Theorem.

It a matter of delta-T and the work required to achieve some delta-T.

As a freezer, asking a box to get 60 - 0 = 60 degrees colder is an act against nature. To perform this act, considerable work is required.

As a refrigerator, asking a box to get 60 - 38 = 22 degrees colder is a lesser act against nature. To perform this lesser act, less work is required.

Es claro?

Also, I've heard people wondering as to why a converted freezer was so much more efficient...

Some say that it is because you don't dump air every time you open the door. I doubt that this is such a great factor, because the energy to chill down a freezer full of air is not so much.

Some say it is because the insulation is thicker. This would be a pretty large factor. That was one of the reasons I jumped on this unit, because it didn't have much more insulation than a refrigerator.

Some say that it is because the freezer is built to be more efficient, else the cost of operation would deter people from owning one. I think that this actually might be true. At least comparing my conversion and what I estimate it's energy use to be, to a refrigerator of the same size. So with a converted freezer, you're taking a fairly high efficiency refrigeration system and lowering the physical demands on it.

Thicker insulation would be better...

Not dumping air would be better...

Not stooping over to get a cantaloupe is not so bad.

-AC

AC_Hacker 05-02-13 02:41 PM

Quote:

Originally Posted by creeky (Post 29731)
...the miracle fridge is 12 cuft and has a freezer ...

If I had 12 cubic feet of space, rather than 5 cubic feet, I'd have 12 - 5 = 7 cubic feet of extra space for food to rot.

For my lifestyle, more space in a refrigerator is not more better... lower utility bill is much more better.

As to the freezer, I have a very small one down cellar. Don't need more.

If you're going to 'roll your own' thermostat, I'd suggest using a 1-wire temperature sensor... more accurate. An LED display would be nice too, but I was in a real hurry to prove or disprove the concept. The thermostat I ordered has a display, and I was able to use the Arduino serial monitor to see what was happening during testing.

Good luck with your search and conversion!

-AC

AC_Hacker 05-12-13 02:59 PM

4 Attachment(s)
The waterproof 1-wire sensors I ordered from China for my Freezerator (newly coined term) arrived a couple of days ago. Cost per each was about $3. Time to receive the shipment was just about forever.


I made a header for one of them that would be compatible with my Multilogger that is shown below. Also shown is the 4.8v power supply from a cell phone charger:


The Multilogger already has a 1-wire compatible header, so my waterproof 1-wire sensor makes the second sensor that the Multilogger will be reading.

I plugged the logger in and put the sensor into the Freezerator, and this is the graph that was produced:


You can see the sensor inside the Freezerator get colder, until it reaches the inside temperature. Also visible are the undulations as the compressor kicks in periodically to maintain the temperature.

The 'blip' around the 37 minute mark was when I got some orange juice from the Freezerator.

The upper data line is the 1-wire sensor that in on-board the Multilogger. Interesting how it is out of phase with the inside sensor. This is because there are condenser coils on top of the Freezerator, as well as the back and both sides. So the compressor extracts heat from the inside and dumps the heat on the outside.

* * *

I have used the Freezerator for almost eleven days, and have something of an initial user report...

Over that time the watts per day has averaged 414 w-hr/day. More than the Bosch miracle fridge, but still quite respectable.

The idea of converting the freezer to function as a refrigerator has worked out well, as I had hoped it would... even better actually.

On hindsight, my initial comparison of the energy saved was an apples to oranges comparison after all, because I was comparing the same machine running in two different modes, freezer mode and refrigerator mode, so it's pretty much a no brainer that refrigerator mode would use less energy.

A better comparison is to compare the Freezerator with different units that are designed to function as a refrigerator.


If I compare the Freezerator to other refrigerators that are of the same size and are in the same order-of-magnitude price category, like the Danbury all-fridge which consumes 901 watts per day, the comparison remains very favorable.

* * *

On the user side, there are issues still to deal with because small upright freezers are designed to accommodate manufactured food packages. I have noticed that some agreement seems to have been made as to what the dimensions of manufactured freezer food packages would be.

So the door storage and to a lesser extent, shelf storage, do not easily accommodate food packaging that has been standardized for refrigeration. Therefore, food repackaging will be required. This is not all together a problem for me, because I would prefer that the contents of my refrigerator NOT be a battlefield of competing brand names. I would much rather open the refrig and just see food.

The door storage may present a special problem, and I may end up reconstructing the inside of the door all together.

* * *

There is also the whole idea of the way this refrigerator, and almost all currently available refrigerators are designed...

In older refrigerators, there was a condenser coil that was held away from the back of the refrigerator. This is where most of the heat from the compressor and the inside of the refrigerators was dumped.

Now refrigerators, which are after all, six-sided boxes, have heat being dumped into 4 of their six sides, which is in direct contact with the insulation. Most of the heat does go out, but placing the coils in direct contact means that on 4 out of 6 sides, some percentage of the waste heat goes back into the refrigerator, where it will need eventually need electrical power to be removed, etc., etc.

From the viewpoint of the user of the refrigerator, this is not good design because it means that power bills will be higher than they would be otherwise.

I can see that the manufacturer would like this idea, because the internal condenser coils are much less prone to damage in shipment.

I think that a motivated EcoRenovator can do much better in designing and building a high efficiency refrigerator.

Best,

-AC

AC_Hacker 05-13-13 02:24 PM

Inscrutable Thermostat...
 
3 Attachment(s)
The inscrutable thermostat (AKA: WH7016 Ultimate) arrived today. It only took 11 days, but it feels like that many months.

Here is a photo of the unit:


The appearance of build quality looks pretty good.

Here's a photo of the top of the unit:


The silk screen matches the terminals on the back... so far we're good to go (but what are terminals 5 & 6 all about?).


There are also instructions included:


...this is where it could get sticky.

I Googled the model number and found instructions in English that appear to jive.

So I have learned that the unit is intended for Peltier Junction control (may be a problem), uses a Sensor NTC 10K / 3435 thermister for the temperature sensor, and that the display is only in Celsius (not a deal breaker) and that there is a menu system that must be used to enter the desired set-point, and upper limit set-point, and lower limit set-point, and upper-limit alarm, and lower limit alarm, and hysterisis.

Sounds interesting so far. Could turn out to be a Chinese puzzle.

More later.

-AC

AC_Hacker 05-14-13 01:48 PM

The Inscrutable Thermostat Menu
 
7 Attachment(s)
I worked on the thermostat this morning, the menu in particular, and I found that there were actually some aspects where the where the Chinese 'manual' and the downloaded 'manual' and the menu in the device that displays on the front of the thermostat, actually agree... but then sometimes not so much.

So here is what I found out...

This is a typical display, there are two LEDs that may or may not be lit, depending on their status on the left side of the display. Right now the display is showing the temperature and neither of the status LEDs are on.


The upper LED, 'WORK' comes on whenever the internal relay is active and off when the relay is inactive.


The lower LED, 'SET' comes on whenever the 'SET' mode is active, and goes off whenever the set mode is not active.


To set the temperature to the trigger point at which you want the thermostat to turn on (or off, depending on whether you want to use this device to control cooling or heating) you push the 'SET' control once and use the up and down arrows to set the 'trigger point'. The display will return to the usual display in a few seconds after sensing no activity from the buttons.


To enter 'MENU' mode, press the 'SET' button and hold for 3 or more seconds.


I found 6 menu items, and they were: HC, P7, CA, H5, L5, and d.


This is the 'HC' menu item. press 'SET' again and you will enter the HC menu, where you will be able to choose 'HC' (for chill) or 'HH' (for heat). HC will allow you to use the thermostat for a cooling device (turning on a cooler if the target temperature is exceeded). Likewise, HH will allow you to use the thermostat for a heating device (turning on a heater if the target temperature is too low).


This is the 'P7' menu item. It is supposed to be understood as 'PT'. The range of values available was 0 through 10.


This is the 'CA' menu item and it is used for calibration. You can use this to shift the displayed temperature to agree with the actual temperature. I found I needed to use this. The thermistor was accurate at room temperature, but at refrigerator temperature, it was off by 3 degrees C or more. I was able to adjust the displayed temp to very accurately agree with a more reliable thermometer.


This is the 'H5' menu item. It is supposed to be understood as 'HS'. The range is large. With this menu item, you can adjust the upper temperature range. Possibly this can be used for an alarm?


This is the 'L5' menu item. It is supposed to be understood as 'LS'. The range is large. With this menu item, you can adjust the lower temperature range. Possibly this can be used for an alarm?


This is the 'd' menu item. It is used to adjust the hysteresis of the system. Perhaps the 'd' means 'deviation', and so allows the user to set the deviation range before the thermostat triggers, thus preventing short cycling.

[NOTE: Both the Chinese instruction manual that came with the thermostat unit and the English on-line manual indicated that there were more choices available in the menu, specifically choices for setting alarms (which could be very useful), that did not appear in the menu of the unit I received. Possibly terminals #5 & #6 that have Chinese descriptors are for an alarm.]


This is what I have uncovered so far... not yet complete.

I am still running the Freezerator with the old Teensy thermostat, and I have the WH7016 running in parallel, monitoring its readout and the status of the output relay.

When they are pretty close to equivalent, I'll switch over.

Best,

-AC

jeff5may 05-14-13 03:46 PM

Awesome! I've seen these controllers on ebay but have yet to pull the trigger on one. Let us know how it works and if not more trouble than it's worth, I may end up using one in the next monster project. The price seems too good to be true, but if the thing actually does its job well, that would be great! I look forward to your opinions on the unit.

AC_Hacker 05-15-13 01:38 AM

The Inscrutable Thermostat works just great!
 
1 Attachment(s)
I switched over from my Teensy thermostat to the Chinese model I bought on ebay, and the inscrutable thermostat works just great!

Here is a log of operation:


The new thermostat works just fine. I have the hysteresis set to minimum (1) and the temp swings are as you see above.

I did a previous run, then adjusted the temperature set point up one degree, to 3 degrees C which would be 37.4 degrees F.

Previously, the lower swing got too close to freezing, which can be rough on produce, so now the adjustment is about right.

The temperature swings with the Teensy thermostat were smaller, and the compressor kicked on more frequently. I'll do a power calculation after a couple of days of running to see if there is any change in power use.

* * *

My goal was to see if an upright freezer, when converted to refrigerator duty, had any appreciable power savings over a comparable refrigerator. My tests indicate that the converted freezer will use roughly half the power of a comparably sized refrigerator. In this case, I used a rather unspectacular freezer candidate (NOT Energy Star), and it is performing much better than the same-sized Energy Star refrigerators. I would expect that if I had started with an Energy Star Freezer, the resulting Freezerator would have performed even better.

Doing this conversion with a cheap Chinese thermostat is really easy.

Now that I have some modest experience with Teensy/Arduino, making my own thermostat was really easy, too.

So, all in all, this has been a very successful project.

Best,

-AC_Hacker

AC_Hacker 05-15-13 07:18 PM

Wrap-up
 
1 Attachment(s)

A final wrap-up on the Freezerator...

I did a calculation on the energy used over the last 24 hours and 58 minutes, and the daily power use, calculated for a 24 hour day, was 278.74 w-h/day. which sounds astoundingly good, but the weather has been on the chilly side, and since I don't heat my kitchen unless it is a byproduct of cooking, it has been cool in there, and as can be seen in the chart above, the regular temperature in the kitchen is in the low 60's.

I intentionally made sure that the Mulitlogger board, with it's own 1-wire temperature sensor was close to the top of the refrigerator so that the heat given off by the condenser would be clearly shown.

Again, it is clear that the work of the compressor is an inverse image of the temperature inside the Freezerator. Pretty good indication that if you have one of these refrigerators with internal condenser coils, you don't want to inhibit airflow to that surface. In the case of my Freezerator, the back, the sides and even the top is a heat-dump surface.

The discontinuity at the 50 minute mark was me getting food for lunch.

All is working well.

-AC

Daox 05-16-13 08:22 AM

Very nice work AC! Thanks for sharing.

ham789 06-06-13 08:13 PM

What was the roadblock to just using the freezer thermostat?
Maybe with some tweaking of the range...

AC_Hacker 06-06-13 08:27 PM

Quote:

Originally Posted by ham789 (Post 30163)
What was the roadblock to just using the freezer thermostat?
Maybe with some tweaking of the range...

That would be a good idea... if you can get to the range you want.

As an after-note, I am finding my particular thermostat to be problematic, as it only adjusts in whole degrees C.

I'm going to return to the Arduino thermostat... much tighter control, both of temperature and hysteresis.

It turns out that 'just right' and 'too much' are very close together.

-AC

Daox 06-07-13 08:32 AM

How do you have it setup to run with the Arduino?

Mobile Master Tech 06-07-13 08:53 AM

Not bad! My 15 year old Maytag full size freezer-on-top fridge takes around 1500 watt-hours per day.

AC_Hacker 06-07-13 09:44 AM

Quote:

Originally Posted by Daox (Post 30169)
How do you have it setup to run with the Arduino?

The first post in this thread illustrated the controller.

I'm using the word Arduino interchangeably with the word Teensy. They are the same thing, with the exception of the reference number of some of the pins. The body of the code just the same. In the head of the code, the pins are defined, and you just reassign the pin numbers to the appropriate Arduino pin numbers.

I can get 'imperfect' Teensies for $10 each, plus I personally know the guy that designed and makes them. That's why the Teensy.

But, I like 1-wire temperature sensors way better that analog sensors, so in 'rev 2' I will be using 1-wire. This will require that I include a 1-wire library, the rest should be very similar.

Also, now that I am aware of how critical temperature adjustment is, I'll make sure that my temperature-relevant variables are floating point and not integer.

Best,

-AC

Daox 06-07-13 09:58 AM

I mean what is your temperature setting and allowable range? A quick look at your code suggests 38 +/- 2 degrees F. But your latest posts seems to suggest you want the temperature held more steady.

AC_Hacker 06-10-13 09:06 AM

Quote:

Originally Posted by Daox (Post 30176)
I mean what is your temperature setting and allowable range? A quick look at your code suggests 38 +/- 2 degrees F. But your latest posts seems to suggest you want the temperature held more steady.

OK, just to make sure that we're on the same page, I ordered a Chinese thermostat, and while I was waiting for it to arrive, I hacked together a Teensy (Arduino) thermostat that used an analog temperature sensor. Aside from the fact that it didn't have a temperature display, it worked pretty well.

Then when to Chinese version arrived I started using it (and as of this writing, still am). That's when I noticed the too-large swings and too-large steps in targeting the set-point temperature.

The reason this is important is that it looks possible to me that this setup may be capable of keeping food acceptably cool while avoiding most, if not all problems associated with frost buildup. This is because the chill area is larger than in a normal refrigerator, and the temps don't have to go as low in the evaporator coil to provide the cooling. It's the same thing as low temperature heating, only this is high temperature cooling. Low exergy, etc.

So, the behavior of the Freezerator seems to be such that if I can get right at the 'sweet spot' it should work better.

I have found that there is an optimum hysteresis swing amplitude, and that if the hysteresis is too tight, the compressor cycles too often, and that uses up more energy... if it's too loose, the system bounces between food-too-warm and frost formation on the coils.

Another issue connected to frost buildup is that making frost requires the refrigerator to supply additional energy that would not be required if I can avoid too-cold temperatures or too-low hysteresis swings.

A third issue with frost buildup is that it has a de-hydrating effect on produce, and shortens its storage life. Since I am becoming a vegetarian, this is a big deal. I have noticed that in general, the humidity inside the Freezerator is unusually high for a refrigerator, and my produce like it that way.

Another issue with the Freezerator Rev 1 is that my previous analog sensor was exhibiting irregularity that may have been due to humidity... I don't know for sure, but I do know that keeping the sensor dry is a good thing.

So in the next revision, I want to use a 1-wire sensor that is properly protected from humidity. And I want to make sure that I have precise control over temperature and hysteresis. And a display, and a proper interface that will give me the ability to change the set-point and hysteresis by using buttons rather than needing to hook up my PC to my refrigerator.

Hope this addressed your question.

-AC

Daox 06-10-13 10:32 AM

Thanks, that was a great answer. How do you plan on going about testing for this sweet spot?

jeff5may 06-10-13 01:47 PM

So what is your overall impression of the chinese temp controller? I mean, other than your desire for total control of all parameters (which may or may not be possible with the off-the-shelf Chinese unit), how does the unit track and/or learn or respond to its environment? I see it strayed or drifted a bit on you. I'm seriously considering using one to control some sort of heat pump monster in the near future. Regular heat pump thermostats are not that much more expensive, and some have lag and swing controls built in also. Probably not as wide-range as the Chinese unit, but then again the temp sensors don't drift either.

Some of your frustration may be built into the deep freeze itself. I'm sure the unit was built for lower ultimate temp, rather than rapid pulldown. With a cap tube setup, this means lower mass flow and suction pressure, regardless of ambient or box temp by design (longer cap tube). It may not be advantageous to try to limit your box temp/evap temp to prevent frost unless there is some kind of airflow inside the chamber.

With the teensy controlling things, you might be able to add more sensors and gain insight into the temps of everything, but with the stratification and lag (due to the lack of airflow) in box temps, I'm not sure it would do so much good. As temps get close to freezing, you may NEED to have frost to transfer enough energy out of the box. I guess it all depends on how short you want the cooling runs to cycle vs the inherent lag.

AC_Hacker 06-11-13 07:51 AM

Quote:

Originally Posted by Daox (Post 30239)
Thanks, that was a great answer. How do you plan on going about testing for this sweet spot?

First is build the new controller. I already have all the parts, including a water proof 1-wire sensor, and a spare LCD I can use for the readout.

After that it will be closely monitored trial & error.

I was scheming a way to make the Teensy (Arduino) automatically increase & decrease the hysterisis until the unit reached maximum efficiency, but then reality set in and I decided that trial & error would the best approach to a one-shot problem.

-AC

AC_Hacker 06-11-13 08:03 AM

Quote:

Originally Posted by jeff5may (Post 30246)
So what is your overall impression of the chinese temp controller?

It is working pretty well. It has a menu for correcting any gross errors in the sensor, it has buttons for easily setting the set-point temp, and also for the hysteresis.

It doesn't have any kind of 'learning' ability, liked PID controllers. It doesn't have the ability to do a delayed start.

It can be used for cooling or for heating through a menu selection.

Apparently, it was designed for controlling a peltier cooler or heater that needs no consideration as to delayed start. It has a relay output and inductive loads will probably shorten the relay life.

It is simple and cheap and works.

-AC

Daox 07-15-13 09:39 AM

How goes the trial and error? Have you been able to reduce the power consumption any further?

AC_Hacker 07-15-13 01:28 PM

Quote:

Originally Posted by Daox (Post 30647)
How goes the trial and error? Have you been able to reduce the power consumption any further?

Thanks for asking...

My data logger is now doing duty as a whole house temperature logger, so I'm not sure what is going on with the power consumption. I am sure it is higher than it was when the weather was cooler, but I don't know how much.

But the Freezerator is working well. As I said previously, the humidity inside the box is higher than the typical refrigerator. This is very good for produce, which lasts far longer than in a normal refrigerator. It also presents a challenge. Right now, I'm dealing with it by using a water absorber pad in the bottom of the unit. A better fix would be a drain tube.


This Haier:


...has a drain tube built in and it's un-hacked specs are very attractive, so it would be a better choice for a Freezerator.

I'm considering the possibility of putting a drain tube into mine. If I could use some kind of heated cone-shaped metal and heat-form a dimple in the bottom of the lining material, then a drain would be quite possible.

But I could just sell my present unit on Craig's List and get the Haier, to hack into a much better Freezerator.

& & &

But my focus is now turning to putting in a radiant floor in my back room... I'm right now emptying everything out in preparation for demolition.

I have finally located some high-density insulating material to use under the PEX & aluminum.

More on that later.

Best,

-AC

oil pan 4 07-16-13 11:18 AM

This is very impressive because a lot of older frigs I have tested consume around 2kwh to 2.5kwh a day. A lot of people complain that the new energy star fridges don't use much less power than some of the older fridges with the large exposed rear mounted passive condenser.

Energy star my ***.

If you saw my post http://ecorenovator.org/forum/geothe...elsewhere.html
You would know my fridge isn't doing so well these days. It seems like it comes on all the time but that just might be because I notice the bathroom fan every time its on. I think I will put one of my Kill-a-watt meters on it and see how it does.
I do have an up right freezer with the large exposed passive condenser I may end up converting to a fridge.

AC_Hacker 07-16-13 02:29 PM

Quote:

Originally Posted by oil pan 4 (Post 30693)
This is very impressive because a lot of older frigs I have tested consume around 2kwh to 2.5kwh a day...

Yeah, it is pretty impressive... partly because it is utilizing the better construction of a freezer, and only asking the compressor to hold 37F or so, instead of 0F. It's also because I'm using a small refrigerator. I have found that I can get by just fine with a smaller system. It's curious that so few EcoRenovators seem to go for the smaller = better idea... oh well.

If you decide to go with a Freezerator conversion, It's quite easy, and if you don't like the results, you can easily switch back.

The Chinese thermostat was about $17. Some people use a beer cooler thermostat, better built for about $50.

I think it is fair to estimate that the Freezerator conversion will use approximately 50% as much power as your freezer normally uses.

It would be a great idea to get a Kill-a-Watt first and establish your freezer's current demand, and also measure the demand after the hack.

There's certainly room on this thread for your story...

Best,

-AC

ELGo 07-17-13 02:12 PM

Brilliant thread.

I came to similar conclusions why freezarators work so well - it is not the horizontal vs vertical orientation so much as just not having a freezer! In a similar vein, smaller is less energy, but again, the bulk of the savings is nixing the freezer.

My Whirlpool averages about 1 kWh a day in our home (rated 1.1 kWh a day by EPA.) It is about 2 parts fridge and 1 part freezer by volume. If I assume fridge temp is 35F (2C) and freezer temp 15F (-10C), and annual ambient about 68F (20C), then all else being equal, the fridge uses 60% of the energy required for the freezer for equal volumes. This means that my 20 c.f fridge/freezer would average 600 Wh a day if it was a 20 c.f. fridge only. If I had only the fridge space of ~ 13.3 c.f., the average daily consumption would be about 400 Wh a day.


I asked my wife if she would be OK with not having a freezer in the house and got shot down. I had to laugh when she said "What about the ice cream ?!" Even she smiled after she thought about her answer, since we make efforts to not gain weight. I'll have to get her used to the idea over time...

About those temperature swings:How about placing some water (in a container to avoid evaporation) in front of the air vent ? Seems to me that you want a solution that will provide buffer and heat capacity. Of course if the cooling device is efficient with short bursts you can just tighten your on and off limits.

AC_Hacker 07-17-13 03:24 PM

Quote:

Originally Posted by ELGo (Post 30717)
...This means that my 20 c.f fridge/freezer would average 600 Wh a day if it was a 20 c.f. fridge only. If I had only the fridge space of ~ 13.3 c.f., the average daily consumption would be about 400 Wh a day.

All things being equal, a smaller frig will require smaller power. But the relationship is not linear, because area increases at roughly a square function, and volume increases at roughly a cubic function... and heat loss is proportional to area.

Quote:

Originally Posted by ELGo (Post 30717)
I asked my wife if she would be OK with not having a freezer in the house and got shot down. I had to laugh when she said "What about the ice cream ?!" Even she smiled after she thought about her answer, since we make efforts to not gain weight. I'll have to get her used to the idea over time...

The old fashioned ice & salt hand-crank ice cream freezers are even more effective than self discipline...

Quote:

Originally Posted by ELGo (Post 30717)
About those temperature swings:How about placing some water (in a container to avoid evaporation) in front of the air vent ? Seems to me that you want a solution that will provide buffer and heat capacity. Of course if the cooling device is efficient with short bursts you can just tighten your on and off limits.

I do know that there is a startup inefficiency, and that longer runtimes favor efficiency. When I get the time, I'm going to return to an Arduino controller, because I can build in finer tuning increments, and as I said before, I'd like to zero in on the most efficient cycle time/temp swing compromise.

There might also be some efficiency to be gained with a suitable Phase Change Material (olive oil?)... but I have too many projects demanding my attention, to pursue that right now.

But, I really like the Freezerator project because it's simple, the reward is easily measurable, and the pay-off comes quickly. Lastly, if you're not satisfied with your hack, no irreversible change has been made to the freezer.

If you're going to try the Freezerator, it's important to find the most efficient freezer you can, whether it is chest-type or upright, because your final energy use will be about fifty-ish percent of the freezer consumption.

BTW, if you get a hand-crank ice cream maker, I have some killer recipes... but don't expect them to be low calorie.

Best,

-AC

ELGo 07-17-13 04:09 PM

Quote:

Originally Posted by AC_Hacker (Post 30719)
But the relationship is not linear, because area increases at roughly a square function, and volume increases at roughly a cubic function... and heat loss is proportional to area.

You are right with large numbers to focus on the exponents, but consider e.g. a rectangle that is elongated in height by 50%:

The surface area increases from
2xy + 2xh + 2yh to
2xy + 3xh + 3yh

While the volume increases from xyh to 1.5xyh.

Not that far off from linear in this range.

By the way, what is the temperature gradient in your fridge from bottom to top ? I'm wondering if extra external insulation on the top of the fridge would have much of an effect.

AC_Hacker 07-17-13 05:34 PM

Quote:

Originally Posted by ELGo (Post 30722)
You are right with large numbers to focus on the exponents, but consider e.g. a rectangle that is elongated in height by 50%:

The surface area increases from
2xy + 2xh + 2yh to
2xy + 3xh + 3yh

While the volume increases from xyh to 1.5xyh.

Not that far off from linear in this range.

If the size of the refrigerators was determined by a chainsaw, this would be correct, but smaller refrigerators tend to become narrower, and sometimes shallower, too.

Quote:

Originally Posted by ELGo (Post 30722)
...By the way, what is the temperature gradient in your fridge from bottom to top ? I'm wondering if extra external insulation on the top of the fridge would have much of an effect.

Yes, it would have a very significant effect.

My Freezerator, as most of the currently produced units, have the integral coils, and the outside surfaces become the heat radiating surface... the top, the two sides, and the back, all have integral coils. So to insulate would have a negative impact on efficiency.

Personally, I think that the integral coils feature costs the planet a huge amount of CO2. Only reason for it that I can imagine is that the coils are much less likely to be damaged during shipping. After shipping, it's down hill.

-AC

oil pan 4 07-19-13 03:41 AM

The current refrigerator we are using is consuming upwards of 5 kwh a day.
I think something is very wrong.

stevehull 07-19-13 05:19 PM

Just thinking here - and provoking AC to give us some thoughts (others too).

Clearly a square box is the simplest way to maximize volume with the smallest surface area (OK, I don't need smart *** comments on this really being a sphere!).

But if we were to built, from scratch, a 'fridge, how would we do it?

I bet we would build a modified rectangle, trying to be close to a cube, but wary of the deep recesses in back where "food goes to die" (quoting AC).

I bet we would choose an external "radiator" with stand offs and not one inside the metal cabinet - likely on the back (assuming an air to air compressor system).

I bet we would insulate with at least two inches of high performance foam (R10 per inch) and I bet we would forgo a freezer to maximize compressor performance with an interior temp of about 40 F.

Since the volume is small, how much water flow would it take to make this a water source compressor type fridge? I bet less than a fraction of a gallon per minute. (I know that as I use a rule of thumb of about 1-2 gallons/minute of water flow per 12,000 BTU of cooling.

Assume a 30 degree delta T with a house temp of 70 F (inside fridge temp of 40F).

Assume an outside 'fridge dimension of 4 feet tall, 3 feet wide and 2.5 feet deep (total surface area of 39 sq feet)

Given the above, what would it take to build this? I don't have my calculator available or I would calculate the net amount of BTUs needed to keep it at this design temp.

I bet a tiny compressor would be needed and a quart of water per minute (assuming an open loop system with a ten F delta T from water well temp to outflow temp.

Now, where could I get a fractional compressor real cheap . . . . (a compressor from a window AC unit would be far too big, same with auto and dehumidifier . . . .).

We all need a 'fridge and I bet this would not be a hard nut to crack!

Just thinking . . . .

Steve

AC_Hacker 07-19-13 08:05 PM

Quote:

Originally Posted by stevehull (Post 30754)
Just thinking here - and provoking AC to give us some thoughts (others too).

Just thinking . . . .

Steve

Good thinking here.

I've done some serious looking into available compressors (probably no surprise there), and small refrigerator compressors are available in the 100 to 200 watt size. Trouble with them is that they use a very strange coaxial cap tube arrangement that seem to me to be difficult to hack, or duplicate. I wouldn't want to discourage anyone from trying, but I was not able to visualize an easy solution. If this cap tube thing could be overcome, the size of the compressor just might be perfect.

On the other hand, very small compressor-type dehumidifiers (as opposed to peltier-junction) can be found. The smallest that I have seen in the wild is a 25 pint per day... which was the guts for my first heat pump. I know that Sears sells a 20 pint per day, with a really small compressor... smallest I know of. The dehumidifier will have a conventional cap tube that will be easy to salvage and re-use.

So, if you're going to do this right, the compressor & condenser should sit on top of the unit, for best efficiency... just like the very first home refrigerators.


Sunfrost uses this kind of arrangement... and their efficiency is legendary... but they haven't brought a water-source unit to market.

I think a good place to start would be to find some kind of pre-made plastic container that would be the right size for the inside of the refrigerator, and build upon that.

Best,

-AC

oil pan 4 07-20-13 02:20 AM

I agree, stuffing the compressor and condenser up under the fridge is stupid.
Over sized passive coils along the back or top coils are best, it almost seems if their engineers forgot about convection.

jeff5may 07-20-13 06:45 AM

Most of the newer (plastic) dehumidifiers are run by either a 4000 or 6000 btu compressor and use R22. The older (metal) dehumidifiers use R12 (ancient) or R134a (old) and have the size compressors in them you are looking for. I have seen a few with mini-fridge style compresssors in them that only draw 150 watts (including the fan). They run much more silently than the newer units. Check freecycle or craigslist in your area.

AC_Hacker 07-20-13 12:23 PM

Quote:

Originally Posted by jeff5may (Post 30762)
...Most of the newer (plastic) dehumidifiers are run by either a 4000 or 6000 btu compressor and use R22...

By "newer", you must be referring to newer used equipment.

R22 equipment is no longer allowed to be sold as new.

But the R22 used stuff is a very good fit for R290, and that makes it very attractive.

-AC

AC_Hacker 07-24-13 07:05 PM

Freezerator Update...
 
I was looking about for a spare Kill-a-Watt, when I realized that I had left one attached to the Freezerator since March (1705 hours to be exact).

So I ran the numbers from the stored data (28.08 kw-h), and I am pleased to say that the average power use calculates to:

395.26 watt-hr/day

(about 1/12th of what oil_pan_4 is pulling from his refrigerator)

It did rise a bit (see photo below) because of the higher ambient temp, but I think that it is really quite respectable.

-AC


Daox 07-25-13 07:52 AM

Very nice. :thumbup: That is about 1/3rd what my fridge uses.


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