Freezer to Refrigerator Conversion

From Open Source Ecology
Jump to: navigation, search

HintLightbulb.png Hint: Good job Dorkmo

/Manufacturing Instructions


Video mentions the refrigerator conversion - video from Open Source PV System


Convert a freezer to a refrigerator, and reduce energy consumption 12x so that your refrigerator uses 8 Watts of average power.

This translates to about 50 million megawatt hours of electricity (126M households with 1 fridge) saved per year in the USA if everyone converted to an energy saving fridge from a 1kWhr/day scenario today. This is about $5 billion dollars saved per year in America.

Nearly every household on Earth has a verticaldoor fridge that uses 100W of power on average - or about 2.4 kWh per day. In a country of a few million households, replacing vertical door refrigerators with chestfridges can save enough energy to allow closing down at least one large power station. Alternatively, construction of a new power station to meet the increasing energy demand could be avoided or delayed.

In money terms, the Superfridge costs 2 cents per day to run (assuming 10 cent per kWh electricity cost). This is about $7 per year - compared to $88 for an average fridge.

For the Seed Eco-Home, the cost is actually even better. The off-grid energy system cost $3000 for 3kW not including labor. This translates to 2 cents per kWh energy cost over a 20 year life of the PV system. That is about $1.50 electricity cost to run the refrigerator for a whole year!

Original Work

This work is based on the Mt_Best_Freezer_to_Refrigerator_Conversion.


Wiring Diagram

OSE Fridge Conversion Wiring.png

google doc

Wiring Harness

OSE - Fridge Conversion v0318 - Wiring Harness.png

google doc


HintLightbulb.png Hint: Transition to Arduino Nano, which is less expensive and appears not to get compilation errors like the Sparkfun Pro Micro

Bill of Materials' lists all parts required to build a machine.



Luxury Edition


  • step drill bit amazon
    • drill
  • butt connector crimper amazon
  • small blade screw driver
  • phillips head screw driver
  • soldering iron - for adding headers amazon
  • electrical tape ace

Arduino Code

HintLightbulb.png Hint: Sparkfun Pro Micro controller appears to require Arduino IDE v1.0.1. Not. See installation notes at

HintLightbulb.png Hint: The trigger values below did not work. See Talk:Freezer to Refrigerator Conversion. Try 300 and 310

Code history - File:Fridge code.ini

//A1 read voltage
//D3 sensor power
//D14 relay (-)

  volatile int sensorvalue = 328; //define the variable
  int triggeron = 328;         //number that will trigger fridge on
  int triggeroff = 304;        //number that will trigger fridge off

// the setup function only runs once every time the chip is reset
void setup() {
  digitalWrite(3, HIGH); //for powering thermister  
  digitalWrite(14, HIGH);  //for switching relay
  pinMode(3, OUTPUT);    //begin operating pin
  pinMode(14, OUTPUT);    //begin operating pin
  delay(20000);          // wait for thermister to get a good initial reading

// the loop function runs over and over again forever
void loop() {
  sensorvalue = analogRead(A1);   //read sensor
if (sensorvalue > triggeron){     //if sensor reads over triggeron, turn on
  digitalWrite(14, LOW);       //turn on relay
  delay(8000);                 //wait 8 seconds
if (triggeroff > sensorvalue){   //if sensor reads below triggeroff, turn off
  digitalWrite(14, HIGH);         //turn off relay
  delay(8000);                  //wait 8 seconds


Refrigerator + Compressor

  • Fridgecompressor.jpg
  • 7.4 LRA on the label. See definition of LRA
  • Info about the panasonic compressor: [1], PDF -[2]
  • Replacement part on ebay: [3]
  • This is the fridge we got (it cost $450): [4]
  • This is the closest (in terms of size and price) currently available: [5]
  • Best Buy has a 10 cu ft for $270 and 14 cu ft for $370: [6]
  • Sam's club has 10 cu ft for $240: [7]
  • Notes on how a Refrigerator Compressor works

Other Options

Further Reading