Keep the Fridge Door Closed--And we have the data to prove it!

Submitted by DaveBakker on Mon, 10/16/2017 - 18:12

keep calm and close the fridge door

We've all hear this a million times from our parents (or said it a million times to our kids). Is it really that big of a deal?

It turns out that the data is pretty interesting, and it's pretty clear that even opening the door about once per hour wreaks havoc with the internal temperature and humidity.

In this brief test, opening the door about every 30 minutes, the fridge used twice as much energy compared to leaving it closed!

I put a PocketLab Weather in the fridge at 9pm - almost bedtime, and let it run over night collecting temp, humidity and light once per second. The reason for the collecting light data is so I can know when the door opens.

Here's a chart of about 3 hours of data starting a 9pm (the memory filled up at about 12,000 seconds):

3 hours of temp, humidity, and light data

Here are some interesting observations:

1. The chart starts at 9pm, when we put stuff away from dinner - it takes about 30 minutes at least for the fridge to recover to base temp, which looks to be about 33 degrees - maybe because of the stuff we put in the fridge was room temp?

2. The fridge was opened twice over the next hour - the temp recovered much quicker, but it's easy to see the warming/cooling cycle is pretty fast, so the cooler is running longer.

3. When the door stayed closed for an extended time, the cooling unit runs about 300 seconds to bring the fridge down to base temp, and then about 600 secs off - so roughly a 30% duty cycle.

It's easy to see that for the first hour when the door was opening and closing, the duty cycle was much higher than 30% - from the first hour I estimate that the cooler was on about 60% of the time - twice the time!

So the bottom line: with the door opening and closing, it is possible that the fridge is using twice as much energy!!

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