Saturday, November 23, 2013

Flower Pot Heater

After seeing a Youtube video of a radiant heater made from some clay flower pots and a couple of candles, I had to give it a try. Naturally the comments were full of hand wringing hysterics wailing about how unsafe it was and how we'd all set ourselves on fire. One particularly shrill nannypants, who apparently stalked down everyone who had made a similar video in order to voice his objections, insisted a child would see the video, create the heater, and subsequently burn to death, and he of course would be there to offer his "common sense testimony" to the lawsuit that the video maker would earn from it.

I really hate the nannypants crowd.
Unlike the video makers, I didn't want this for my house but for my aquaponics cold frame. I figured I could set one under each grow bed and create enough heat in that small enclosed space to keep the system comfortable during the worst of the winter.  Off to Home Depot we went to get supplies for two flower pot heaters.

Some people used two pots, others went with three. Since the little pot was only .78 I figured I'd do three. Each heater required one 8" pot, one 6" pot, and one 3" pot, plus a 6" saucer, one 5/8" x 6" carriage bolt (not galvanized), six 5/8" x 1 1/2" washer, and three 5/8" hex nuts (again, not galvanized). You also need some candles and two bricks to set the pots on. Home Depot had small pavers for .48 each so I got two of those. I had a bunch of votives so I grabbed one of those, but if this works like it should then I'll order the 10 hour votives in bulk online.

Your pots will sit down into each other like this.

Always use a washer wherever there's contact with the pot. It'll go Bolt, Washer, 8" Pot, Washer, Nut, Washer, 6" Pot, Washer, Nut, Washer, 3" Pot, Washer, Nut. You want them snug but not tight because you risk cracking the clay. These cheap terracotta pots are rarely fired properly. I used to have a friend with a pottery studio who would let me use her kiln to refire my clay pots and they lasted so much longer, but those days are gone along with my misspent youth.

In less time than it usually takes me to drop a brick on my foot and hop around the garage swearing, I had both flower pot heaters finished. I wanted to try them out, but in a rare flash of common sense decided the top of the freezer might not be the best place to fire things up.

This was a complete bust. One votive barely made the pots warm. Three made the pot warm but if I moved the thermometer two inches away the temperature showed no difference in the surrounding air. If all you need is something warm to put your cold hands on, it's great, but to warm a room? Um, no. The candles kept extinguishing themselves, and even when they didn't it did nothing to warm the surrounding air. If anything the pots stole all the heat. 

I ended up pulling these out from under the grow beds and putting a foil lined pie pan with 4 votive candles under instead. Temps dropped to 20F but the bare naked candles kept things going just fine. However, after crawling under there every 10 hours to replace candles, I wised up and shoved a little space heater under instead.

Yes I know putting clay pots over a candle won't magically make it put out more BTU, but the thermal mass idea made sense as far as storing the heat up. Oh well, one of them did wind up making a nice hand warmer on my desk. :)

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