I finally got the chance to set up my chest freezer as a fridge a couple of weeks ago, and I’ve been testing it out so I could write up this post.
You may recall I mentioned that we had an old fridge/freezer running in our garage as a second fridge. With three young kids in the house, we go through a lot of milk, juice, yoghurt and wine. Having a second fridge lets us buy larger quantities of these things once a week, instead of needing to go to the shops every day or two.
I measured the energy use of the old clunker with my MS5116 mains power meter, and was surprised to learn that it was using 2.5 kWh of electricity per day. Our total household energy consumption at the time was around 20 kWh per day, so this thing was responsible for 1/8th of that!
A lot of hard-core sustainability geeks around the internet (especially those living off-grid) have toyed with the idea of converting a chest freezer into a fridge. The theory is that it will use a lot less electricity because the horizontal lid doesn’t let the cold air fall out when it’s opened, and it has very thick insulation compared to a fridge. People are claiming some amazing power consumption figures, but would it really work that well?
I bought a 210L chest freezer for $90 second-hand, and ordered a FridgeMate MkII digital temperature controller online for $50.
A little bit of wiring is required to set up the digital temperature controller. It’s basically a temperature sensor that can switch a 240v power supply on or off. The simplest way to install it is to take a short electrical extension cord and cut it in half. You can then strip back the wires and connect them into the back of the FridgeMate according to the supplied wiring diagram. This gives you an extension cord with a temperature controller in the middle. One end of the power cord plugs into your powerpoint, and the freezer plugs into the other end.
The photo below shows how mine is wired up – it should help if you’re having trouble following the schematic wiring diagram. In the photo, the right-hand cord is the end with the male plug (i.e. that plugs into the power point) and the left-hand cord has the female plug (i.e. where the fridge plugs in). The cord in the middle with the red and white wires is the temperature sensor, which needs to sit somewhere inside your freezer but not touching the walls. For safety, the controller should be mounted in a project box so nothing can come in contact with the live wires on the back of it.
The FridgeMate can either cut the power when the temperature rises above the set point (if you’re using it to control a heating mat or belt), or it can cut the power when the temperature drops below the set point (if you’re using it to control a fridge or cooling coil). It has a lot of configurable parameters, and comes with an instruction book on how to modify them all, but the instructions list out the recommended settings for use with a fridge. This makes it very easy to program.
Once it’s all set up, the freezer can be plugged in and the power turned on. It didn’t take long for my little freezer to drop to my set point of 3 degrees C, at which point the FridgeMate cut the power. I then opened the lid for a while, and as the temperature rose the FridgeMate cut back in and cooled it down again. Perfect!
So, how much electricity does my chest fridge use?
Once it was loaded up and stabilised, I left the MS6115 on the chest fridge for 24 hours. When I came back, it was reading a cumulative usage of just 0.2 kWh! Given the limited 1-decimal-place reading, I’m calling that 0.2-0.3 kWh. Not bad at all – it’s around 1/10th of the old fridge (at 2.5 kWh/day).
And how is it in use?
I thought it was fine, but the true test of the usability of the chest fridge was what Megan thought. After a week or so of use, she’s quite happy with it. We’re keeping all the bottles of milk, juice and wine on the bottom of the fridge. Smaller bottles (beer, ginger beer, etc) go on the step, and items like yoghurt, butter, etc go in the basket. Megan actually finds it easier to lift and rearrange the bottles from above than to slide everything in and out on a normal fridge shelf. You have very easy access to everything in the fridge without having to move stuff around.
Someone asked me what the ambient temperature was when I did these power tests. I didn’t actually measure it at the time, but it would have been around 20 degrees C during the day in the spot where the fridge sits. It probably dropped to about 10-12 degrees C overnight, I’d guess.
Saturday, 23. May 2009
To quote from the text: “With three young kids in the house, we go through a lot of … wine.”
So I got to ask, is it the kids who go through the wine, or the parents because of the kids?
Saturday, 23. May 2009
@Jason: It was intentional – the parents go through the wine because of the kids
. A decent amount of home-brewed ginger beer seems to be consumed, too.
Sunday, 2. August 2009
Hi Darren-
I want to try this set up stateside in a camper… I have found a vendor for the Fridgemate MkII in a 110v model, but the description says nothing about whether or not it can handle the kickback of an inductive load. Are you implementing a relay or capacitor to handle inductive load, or does the MkII have a built in capacitor?
I am referencing Tom Chalko’s PDF document from mtbest.net on this subject. Within said document Tom states that the Jaycar WT2300 thermostat he tried first failed after six weeks of use when the relay started suddenly producing large and bright plasma arcs in his kitchen!!
I am REALLY trying to avoid anything that could be a fire hazard, and so the relay contacts must be able to handle inductive load.
It seems a nobrainer… if yours is still working, then it must be able to handle it??
Sunday, 2. August 2009
@James: To be honest, I’m not sure about how well it handles an inductive load. But it is a “fridgemate”, designed to switch fridges, so I would have to think it can handle them OK. The Jaycar thermostat may be of a more general-purpose design and that’s why it couldn’t handle the job? Dunno. I did see one chest fridge conversion that added a circuit to dampen the startup spike, for use with batteries and an inverter – possibly it was the Mt Best one, but I can’t recall. My FridgeMate is still working fine!
Sunday, 16. August 2009
Thank you for posting this, nice to finally see that at least one other human being, after Tom Chalko, has taken up the challenge to produce what the entire global refrigeration industry has failed to provide. I intend to be the third, unless I can find a commercially made version.
I am outraged that this is not made available to regular consumers. Have I just not been looking hard enough, or is the concept of chest fridges really that rare?
Monday, 24. August 2009
@Yosh Hash: I know of a few people who’ve done this, I guess most of them don’t have blogs or feel the need to tell everyone about it like I do
. The big problem with chest fridges going mainstream is the amount of testing etc involved in bringing a new appliance to the Australian market. There’s a lot of testing for electrical safety, standards compliance, Energy Star rating, etc that the manufacturer has to pay for before they can even sell one unit. And let’s face it, these things are never going to sell as many units as an LG side-by-side with water and ice dispenser.
It’s a pity, but then I don’t think they could make them as cheap as my one anyway! It really wasn’t hard to set up, and it’s been working great so far.
Let me know how you go!
Saturday, 3. October 2009
Hi Mate
Have just been reading your website. Just wanted to thankyou. Throughly enjoyed the read. Some great info.
Cheers Patrick
Monday, 5. October 2009
http://www.haieramerica.com/en/category/Home_Appliances/Freezers/Access_Plus_Dual_Zone_Freezers
Well, well, it seems there is at least one actual manufacturer. Haier apparently sells a lot of products to major retailers like Walmart and Home Depot, so it shouldn’t take much to have them stock it- people just need to ask for it and buy it. Here in Canada, they don’t seem to have them, but I’m going to keep making inquiries until they do.
Tuesday, 6. October 2009
@Patrick: Thanks mate, hope it was of some use (or at least entertainment!) to you.
Tuesday, 6. October 2009
@yoshhash: Thanks for the link, that’s really interesting. If anybody sees one of these in a store, please let us know!
Wednesday, 21. October 2009
Hi Darren Thanks for posting this! I am interested in converting a chest freezer to a “can cooler” for cooling my milk– I milk goats and don’t have enough of them to merit a bulk tank. I know of people who have done this and love how it works. Basically it will be a freezer filled with water that is kept just over freezing level.
I think the process would be the same as yours except that I am going to have water in mine and will need to seal the joints with caulking. My question for you is did you cut the original thermometer out of the freezer? What was this process like?
Thanks for any thoughts.
Wednesday, 21. October 2009
@Trillium Hill: There are two general approaches people use. One is to replace the existing thermostat with one that works at a higher temperature range (i.e. replace the freezer thermostat with a fridge thermostat). The other is to do what I did, and use a digital temperature controller with its own thermostat to simply turn the mains power on and off.
For your project, I’d try to find a waterproof tub or box that fits inside your chest freezer rather than sealing the freezer itself with caulking. The caulking may eventually leak. If you use the digital temperature controller method, you could put its temperature probe in your water bath and then set it to maintain a temperature just above freezing. That should work nicely.
I like your web site by the way (assuming it’s trilliumhillfarm.com, and not trilliumhill.com!). Vermont looks beautiful, and I’d like to get over there someday. My neighbour’s daughter and her family live on a farm somewhere in Vermont too.
Thursday, 3. December 2009
I’m very interested in this idea as im currently moving out of home and looking at purchasing a fridge. Since a fridge is a hefty investment, I’d like to think this solution would be the best.
My main concern is, what do most people use for a freezer then? Do they go without or do they run a second unit for freezing?
Also, I’ve been looking at Haier chest freezers, but would you suggest anything in particular to purchase?
Monday, 7. December 2009
@David: We have our two chest freezers side by side – one running as a fridge, and one as a freezer. It’s a lot more economical than the upright equivalent! Sorry, I don’t have the knowledge to recommend any particular brands or models. I’m a fan of buying second-hand, so I’m always limited in choice to what is currently available and I just research those online to come to a decision.
Monday, 7. December 2009
@Darren: I had the same idea, the bonus would be the huge amount of extra storage space for food, but the downside is that having two would take up much more room.