Wednesday, December 19, 2007

Super-efficient "chest fridge" (with pictures)

Okay, since this keeps coming up, I thought I'd explain how we converted an old chest freezer into an amazingly efficient refrigerator. Now just to be clear, this was not my idea originally. I can take zero credit for any part of this concept. I'm just following in the footsteps of smarter people than me. The original concept came from here, and honestly, I've lost track of where I heard the suggestion for using the homebrewing thermostat instead of doing the wiring yourself.

Before I get to the pictures, let me tell you how "amazingly efficient" it actually is. Our "efficient" bottom-freezer upright refrigerator is rated at 594 kWh per year. This converted chest freezer should come in at about 55 kWh per year. To put this in perspective, that's about the same as two 15-watt compact fluorescent bulbs turned on for five hours a day. (Disclaimer: It's a good bit smaller than our conventional fridge, and has no freezer. But still...)

Okay, on with the pictures...

Here is the (former) freezer. It's a 5.5 cubic-foot GE, rated (as a freezer) for 242 kWh per year.
As you can probably tell, it's in our basement. The basement air will always be cooler, giving this little guy less work to do. It's also in close proximity to the area that we hope will become a root cellar, which, if we can enclose it and give it an outside air vent, will give the chest fridge almost no work to do. At least in the cooler months. (And if you look closely, you'll see our worm bin off to the side.)

Here is the external thermostat (purchased here for about $60). For the record, the thermostat is mechanical, not electrical. It consumes no power.

(this photo borrowed from HopTech)

Here's a close-up of the thermostat itself. Couldn't be simpler...

Here's a photo showing how the fridge plugs into the thermostat's cord (which then plugs into the wall).

Here's the temperature probe, held precariously in place by duct tape. It's best to keep the probe out of contact with the inside walls. After all, you want to control the air temperature, not the surface temperature of the wall.

You may not be able to tell from the photo, but some condensation does form on the inside. We alleviated this by opening the little drain plug in the bottom of the freezer (used for defrosting). No water drips out, but it seems to reduce the amount of condensation inside.

That's it. Five minutes to hook it up. No tools or expertise required.

It was using about 0.18 kWh per day in the summertime, and it's down to about 0.12 kWh this winter.

(And a big thanks to my camera for working. The little pocket one wouldn't have been able to cope with our basement at all.)



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At 12/22/2007 4:13 AM, Blogger Lisa said...

That is so cool (pun intended!) I will have to file that away for future reference. Thanks

At 8/14/2010 1:49 PM, Anonymous Anonymous said...

I. Am. SOOOO. Jealous! I've wanted to do this for a long time, but my husband says it looks stupid and it's not really efficient (it's a hoax or something), so he's not on board. Ah, well!!



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