I Tried the Terra Cotta Heater

I Tried the Terra Cotta Heater

You know, the one going around Facebook.*

* The video doesn't seem to exist anymore.

Let me explain. Our furnace broke two days ago. We noticed it in the morning when the house was fricking cold and the thermostat was at 57 degrees. Brrr!

Having breakfast wearing all the things

I sent the landlord a note, and he gave me the number for his furnace guy, so I got on the horn and the guy knocked on the door and he looked at the furnace and said the ignition was out. Parts were due to arrive the next day.

The landlord offered to reimburse us on a space heater, but we weren't feeling it. We figured it would be just as easy to wait till the furnace was fixed. I mean, we have blankets. We don't need a heater to get us through the night.

Next day, email from the landlord telling us the furnace folks wouldn't be coming that day after all, and the offer of a space heater stands. We still weren't feeling it. Cold is uncomfortable but discomfort isn't a problem per se. I didn't want to run an errand. Call it laziness. What seemed more interesting to me, and didn't require running any errands, was to make one of those terra cotta heaters and see if the Internet was telling the truth about them or not. When evening rolled around, I decided to try it.

Thermostat showing temperature of 61 degrees F

Boots was skeptical. How much energy does a tea light store, and will the thermal mass of a couple plant pots really radiate that much heat? I said, well it's not thermal mass; it's convection. Who knows, maybe convection is a more efficient way to disperse the small amount of energy that the tea light does store. Maybe it increases perceived heat, even if the total heat it has to offer isn't much to speak of. Point being, I was curious.

Terra Cotta Heater Collage

I set up another one on the mantle. It was tricky to get the candle to stay lit. Took some fiddling. King Sturdy was fascinated and wanted to check on it often. It was his job to blow out the match each time we relit.

Terra Cotta heater on the mantle

The terra cotta heaters were up and running around 5pm. The inner pots were quite hot, the outermost pots were warm to the touch, and if you held your hand over the hole at the top you could feel a nice little stream of warm air.

At 6 or 7 o' clock, the thermostat showed no change. I went grocery shopping. When I got back, what to my wondering eyes should appear? A whole degree of difference!

Thermostat showing temperature of 62 degrees F

Except it doesn't mean anything. While I was out, Boots was washing dishes with whole floods of steaming hot water and also cooking things for the boy, and a hot stovetop generates so much heat. I often drink tea standing next to the burner in the kitchen because the warmth is so delicious. One day I'll have a woodstove.

Anyway, there you have it. Two little terra cotta heaters are not enough to heat a house. Fun, but useless. Of course, there's no saying it couldn't work if you added more candles and tried it in a smaller space, like the guy in the video; then again, he had a computer or two in that office, didn't he? That's where his heat was coming from.

We'll be going with the space heater.

3 Comments on “I Tried the Terra Cotta Heater

  1. Interesting! Our heater went out last winter, but as homeowners, it was my duty to decide what to do about it.

    We woke up to a cold house as you did – 55 degrees. Having no other responsibilities more pressing that day, and being a DIY guy who hates to pay a repairman, I climbed up in the attic and poked and fiddled. A high temp protection switch had been tripped, and it turned out the blower fan was not spinning, causing the gas to overheat the system and shut down. The internet said 90% of the time this certain kind of fan motor dies, it’s actually the control electronics inside that die. Repair places won’t sell to homeowners – HVAC industry only – and the cheapest replacement motor I could find was $400 and would arrive in a week. We ran our (radiant type) space heater with a fan on it to make it work harder and tripped the breaker when running the microwave at the same time. We ran the oven at 200 with the door open (a trick my sister used years ago when her heater broke, only she put a little fan blowing into it also), shut doors to rooms we didn’t need, and kept the house in the high 50s (it was 20s and 30s outside those days). Blankets and coats!

    The next day, being unwilling to spend $400 and wait a week, or maybe $1,000 for a repairman to come, I pulled out the fan and took it apart. Most of these controllers die due to a bad capacitor, which is cheap and easy to replace and I could find one locally. I was pretty shocked to find that it wasn’t actually the controller broken – one of the magnets on the rotor had come unglued, and was sticking to the stator and jamming it. I glued and clamped the hell out of it with Gorilla glue, put it back together, installed it in the furnace, and it’s still working. Score 1 for DIY!

    I saw that terra cotta heater a while back. It’s a pretty good idea – basically the 1-room indoor equivalent of turning a campfire into a masonry heater. Note that he does it with up to 4 candles for what looks like 100 square feet of office. The setup won’t get more heat from the candle – that’s a fixed output – but adding lots of thermal mass to radiate heat instead of letting it fly away into the air helps hold the heat and keep the temp more stable.

    If you’re still feeling like experimenting, the way to scale up to house size is to use oil (Olive works well, just not extra virgin) as a fuel source, and multiple large wicks, in a large container like a dutch oven. This is like making your own kerosene heater. You can use twine-size or larger cotton rope and bend wire hangers to hold the wicks up just above the level of the oil. You’ll need to keep pulling the wick through the looped wire holder as it burns down, and adding more oil as the level drops. But you could get 5-8 large flames from one dutch oven, and if you stack big ceramic planters on top for the masonry heater effect, you’d see some nice heat. Depending on the size and number of your wicks, it would be like running 50 tea lights’ worth of the terra cotta heater.

    Or, just run the oven with the door open and point a fan into it. That takes advantage of the 4-5 megawatts in the oven heater instead of being limited to the 1,500 watts from a space heater. You just can’t take it into the bedroom!

    • Wow, those are great thoughts. I remember when your heater broke … DIY wins again!

      And oh yeah, I actually made my terra cotta heaters before I’d seen the video (of course), so some of the details slipped past me. I was working in a coffee shop when I first came across the link, so didn’t play the sound; then later, when I was making my own, I just looked at what Google images had to say about the setup rather than playing the video. Afterward (today), I watched it and saw he was using four tea lights, whereas my little heaters combined were only running on two. But, like you said, it wouldn’t really make a difference. I’m trying to heat much more than just 100 square feet.

      Your dutch oven oil heater idea is intriguing. I do have oil and a dutch oven. (I also have a kerosene lamp, come to think of it.) And I hadn’t even thought about putting the oven on low – great idea! Will go and do that now.

      • Your kerosene (probably liquid parrafin, actually) lamp will put out a lot more heat than a few little tea lights. It’s all about how big the wick is; a larger wick can burn fuel a lot faster. The upside down pots (or whatever you use for radiant thermal mass – cast iron probably works better) only help distribute the existing heat. Still, hold your hand over the lamp versus the candle – even a few candles won’t burn your hand as fast as a good oil lamp!

        Set a fan on the open door of your oven pointing in, it’ll blow the heat out the top and turn your oven into a nice space heater, with more power and the same efficiency as anything you get at the store. Use the normal space heater in a bedroom. That’s much easier than experimenting with cotton rope and olive oil! But I’d probably be experimenting as well as using electricity – liquid fuels are cheaper than electricity and more fun. If you feel inclined, don’t use extra virgin olive oil – just doesn’t burn very well. Some vegetable cooking oils can work, but I’ve heard mixed results and haven’t tried them.