Living on Solar Energy – Chest Freezer Conversion

All my electricity needs are supplied by my modest .312kwH off the grid Solar System. So to ensure I have plenty of power to charge batteries for my power tools and run my Espresso Coffee machine I decided to convert a 160L chest freezer into a fridge.

The theory is simple, every time you open your upright fridge door all the cold air escapes out the bottom because cold air falls naturally. The fridge motor starts every time the temperature rises inside your fridge and given we let a great deal of cold air out every time we grab a snack or worse stand gazing blankly into the open fridge hoping for some inspiration.

Alternatively, when we open the ‘lid’ of a chest freezer(now fridge) the cold air can’t escape as it is held at the bottom of the chest box.

Running the motor chews up a certain amount of power depending on the size and age of your unit – thus refrigeration demands a great deal of our daily electricity needs next to heating water. So to reduce the power consumption of the fridge makes a lot of sense – common sense really.

So what I have achieved is to control the temperature of the freezer to only cool to 4 degrees C instead of the usual -17 degrees C and due to maintaining cooler temps due to retained cold, my Fridge only runs for approx’ 1.5 to 3 minutes approx’ 16 times in 24hrs. I have timed the motor during the day, so these numbers are really estimates as the ambient heat on a hot day in the kitchen will also impact the results.

Parts Needed:

1 x STC-1000 Digital Temperature Controller available on Ebay. Making sure it is compatible with 220/240V

1 x old or new 1m extension power lead

1 x Utility Junction Box – Jaycar

some small zip ties to secure the wires

Here is a PDF of the instructions I followed but note this person uses a power socket instead of a power lead.

Essentially I repeated the wiring pattern, noting in Australia Blue is Neutral, Brown is active and Green is Earth.

I have now mounted the controller box up high behind the fridge.

The numbers :

My Freezer runs on .7amps/hour = 168W/hour divide this by 60 (minutes) = 2.8W/minute. Multiply 2.8W x 3 minute run time = 8.4W per run time. Multiply this by 16 run times in 24 hours = 134.4W/24 hours = 48 minutes of run time in 24 hours

Compare this to this article of info on “how long does a conventional upright fridge run in a day”.

“This is difficult to answer, because it depends on many factors — how often the door is opened, the ambient temperature, how much is in the refrigerator, and whether new items were recently added to the refrigerator and need to be cooled down.

Most frost-free refrigerators have a timer that runs them for 6 hours, then defrosts them for 30-35 minutes. This means, at the the upper limit a refrigerator might run 24 hours out of every 26 hours, or an equivalent of 22.1 hours per day. (The timer only runs when the compressor runs on energy saving models, so if the compressor motor doesn’t run continuously, the intervals between defrost periods will be longer than 6 hours.)

Once the contents are cooled down, a modern refrigerator in good condition might be expected to run 27% to 37% of the time at an ambient temperature of 70°F, i.e., 6.5 to 8.9 hours per day, and 45% to 61% of the time at an ambient temperature of 90°°F, i.e., 10.8 to 14.6 hours per day.

The only practical way to determine how long a refrigerator runs each day is to connect a run-time counter to the compressor motor circuit and operate the refrigerator for one to two weeks, or longer, then read the total run time from the counter and calculate the average number of hours the refrigerator ran each day.” source

Concluding, I realise not everyone has the patience to rat around down inside a chest fridge to find the salami or last nights pizza, but what I feel is important to grasp is how can we all minimize our reliance on fossil fuels and coal fire powered electricity? The biggest polluters of our time – so isn’t it about time we took our power back by using less energy and using renewable energy sources? Its your future in your hands.

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