03151 Chest Refrigerator

I always think if you have to cook once, it should feed you twice. If you're going to make a big chicken and vegetable soup for lunch on Monday, you stick it in the refrigerator and it's also for Wednesday's dinner. — Curtis Stone

Several years ago, I researched refrigeration options. I found very efficient fridges on the market — all of which were insanely expensive (Sunfrost, et al), starting at $2,000 and going up from there.

Then an internet search turned up these links —

http://mtbest.net/chest_fridge.html

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

These links describe insanely cheap way to get maximum energy efficiency AND energy conservatism for your refrigeration needs.

How? Transform a chest freezer into a chest refrigerator by using an external thermostat to operate the freezer at refrigerator temperatures.

So I got a free chest freezer from a friend, and bought an external thermostat for $60 from an online supply house.

These thermostats are often available at local home brew stores, since home brewers use them to age their brews in chest freezers kept at the proper “beer aging” temperature. See http://tinyurl.com/yjnajkd for an example.

I plugged the external thermostat into the wall outlet, and plugged the chest freezer into the thermostat. I put the sensor (a long coiled wire with a metal sensor at the end) inside the chest freezer, resting it on a piece of metal toward the middle that was probably designed to hold a rack. You don’t want the sensor at the bottom of the chest refrigerator, because cold air tends to sink and the items toward the top will not be properly cooled. I did not do any of the “surgery” on the thermostat described in the articles at the links above, in fact, I think I have a different kind of external thermostat.

I ran the metal wire into the chest refrigerator by simply laying it in place over the lip of the refrigerator on the gasket. The door closes just fine and the gasket prevents any cool air from escaping.

I organize the items inside the chest refrigerator in boxes and a basket. I put frequently used items (like butter and ketchup) in the basket. Meats, dairy, veggies — all have their own boxes. Leftovers go in individual containers right on top, so we use them quickly. I put an empty box with a rack on it (from the refrigerator this replaced) to keep the items up off the floor of the chest refrigerator. Over time I’ve used different boxes. Sometimes they are color coded. Sometimes I write what’s inside on their lids. All the boxes I’ve used are plastic. I have not found boxes made with more sustainable materials that will work in this particular application.

It took about one week to get used to the top down orientation, as opposed to the side view of a conventional refrigerator. It took even less time to get used to a new flat space in the kitchen. Now it has additional functions — sorting mail, staging groceries into the pantry, and food prep. The lid doesn’t accumulate stuff because people open it several times during the day.

After about a year, I replaced the original chest fridge with a new chest freezer. The first one was quite large (18 cubic ft) and that was too big. I replaced it with a 10 CF chest freezer. That works just fine for our household of five.

The chest refrigerator needs to be cleaned each week. Moisture collects on the floor of the chest refrigerator. If the chest refrigerator doesn't connect to a drain hose, you will need to clean that out each week.

The size and efficiency of the original chest freezer matter. I started with one that was older, less efficient, not-so-much insulation, and nearly twice as large as I needed. It’s power consumption was nearly twice the consumption of the smaller/newer chest freezer I bought in 2007.

The brand of external thermostat I have swings 4 degrees on either side of its setting. I keep mine set at 37 degrees.

Why does this work?

In a regular upright refrigerator, every time you open the door, the cold air, which is heavier than the warmer air in the kitchen, falls out. When you open the door of a chest refrigerator, no cold air falls out, since it’s already lower than the warmer kitchen air.

Freezers are much better insulated than refrigerators.

The chest configuration seems to hold more items than the same amount of cubic feet in an upright configuration. With a system of boxes, you can make (for example) your “veggie storage area” bigger or smaller based on how much you have — you just use a larger box or an additional box for veggie storage if you have a lot of refrigerated veggies on hand.

On July 17, 2007, after 184 hours of running (7.7 days), the chest refrigerator had used 3.5 kWh of electricity, or .46 kWh per day. That average daily electrical consumption held steady through the next reading on July 24, 2007, a total of 15 days running. That gave me a base line for the hot months of the year.

I began measuring again in the fall.

On October 27, 2007, after 98.5 hours runtime (4.1 days), 1.31 kWh had been used, or .32 per day. I measured again on January 21, 208, after 507 hours of runtime (21.1 days). During that period, it used 6.09 kWh, or an average of .32/kWh/day.

On June 23, 2008, after 411 hours runtime (17.1 days), the chest fridge registered 8.02 kWh consumption, or .47/day.

So I take .32 kWh/day as the cold season average consumption and .46 kWh/day as the warm season average usage.

This totals an annual electrical consumption of 142.35 kilowatt hours for the chest refrigerator.

A typical American refrigerator consumes between 500 and 1000 kilowatt hours per year. A Sunfrost Refrigerator, which is a super-efficient refrigerator, consumes about the same amount of energy as the chest refrigerator. They cost about $2,200 for a unit that holds the same amount as our chest freezer. We paid about $250 for our chest freezer and $60 for the external thermostat. Our total cost was about $310.