Terra Cotta Heating Plan

As promised, as soon as it's been tested through freezing, I want to share this inexpensive, simple heating idea.  I haven't seen any of the videos, but I'm guessing they are all pretty similar.  Keep in mind there are videos though and other people may have better ideas or more efficient ideas than what I'm doing here.  I got this idea from seeing a Terra cotta fire pit last summer.




As I write, I am conducting experiments on candles, as well as various combinations of pots, but to date, this is what I've been using.  Photo and measures.

I went with a pretty small one, because heat rises and most of my plants in the green house are on the ground right now.  I may use the larger one when I start my bedding plants in January, but it placed the heat too far above the plants.


I have always had my greenhouse off grid, but I've developed different ways of heating it using candles, which I make.  To be honest, candle making isn't one of my pleasures in life.  I can do it, the candles are functional, but it's a necessity, not a hobby!  I've developed a few container candle ideas that really do work well in jars that cannot be used for canning.  Baby food and peanut better jars are my favorites, as the diameter of the mouth of the jars is relatively the same size as the container, for proper aeration for the flame.
This is a one cup measuring cup next to what I believe is the smallest baby food jar.



With longevity in mind, I ordered wax shavings or crystals or whatever the term from a candle supply company.  I don't even melt the wax to make my heat source candles.  I simply put the wax in the jars as it is.  I tamp it, but it's not packed tightly.  Just tight enough to keep the wick stationary.  I then, pour oil over the wax to just under the threaded part of the jar.  These are not decorative candles!  I am completely utilitarian when it comes to my candle making.

The small baby food jars will maintain throughout the night and the larger ones two nights, if it's warm enough in the daylight hours for the sun to warm.  The greenhouse averages 30 degrees above the outdoor temperature on a sunny day, even in winter.


Enough about candles, let's get to the nuts and bolts of this heater.  Two Terra cotta clay pots.  4 washers bigger than the holes in the bottom of the pots, 1 carriage bolt per project, and three nuts that fit the bolt.  The larger heater has a 5 inch bolt and the smaller one is 2 or 3 inches.  Turn large pot upside down and place washer over hole, then put the bolt through the hole.  Fasten a washer and a bolt on the inside, finger tight is ample.  I secured another nut about 1 inch from the end of the bolt, washer, then the smaller pot, with the last washer and nut to the end of the bolt.  Make sure the final nut threads completely on to the bolt.

Some may run the bolt the other way in the project, but doing it this way, I can still set the pot on end, when changing the candle or for storage.    While I was typing this article, I was testing using just one Terra cotta clay pot over a candle and not even enclosed in bricks, just propped up on two cans.  In one hour, a completely new tea light was totally melted just sitting on top of the single 6 inch pot.



The six inch pot in the test is the smaller pot to be used in my 12 inch larger heater, when the time and need arises.

I am using 3 "pavers" in my green house, with one on each side propped on the back one.  I am not sure if it adds extra surface heat to the pavers, thus dispersing more heat, but that's my hope!