This instructable describes the building of a flower pot heater. It does not use tea candles to heat up but can. It uses gel fuel like that used in camping or to keep food hot in catering operations,buffets and such. The pot heater was built as a solution to a problem, specifically that my garage is in the back of my yard, is not insulated and it is cold in the winter here in Toronto, and I can't spray paint in temperatures in the -C's. This passive heater plus an active pot heater will provide the heat necessary to warm up a paint booth 36"x36"x21". This little six inc heater reached temperatures in the central core of more then 200 degrees Celsius and temperatures above 90 degrees Celsius on the outer pot within an hour. I stopped the observations after an hour.
Step 1: Flower Pot Thermal Reactor
Getting the Facts Straight
For thousands of years humans have been heating rocks to serve as heat sources during the night. Advanced per-industrial societies using similar technologies to heat their homes. Fireplaces being one.It is still being used today in poor areas. I don't know who or when somebody came up with the idea of using flower pots as heaters. During my research into this I came across many ideas and permutations on the flower pot heater idea. They all had the same basic parts plus a few other additions, but they all had short comings, that they all treated this as "Oh look at me I made this heater out of flower pots a steel rod some nuts and washers and tea candles". In all of them none of the flame from the candles was touching the rod. Then came the NAY SAYERS, THE TRUMP DISCIPLES trying to debunk the idea with science and to my observation failed miserably, the CHICKEN LITTLES on YouTube commenting that you should not do this because of the toxins in the clay. First of all flower pots are fired in order to seal them so that the moisture stays in for the plant to use. And then there are those I call VIRGINS, they haven't built anything but have the need to comment.
YOU HAVE TO PUT FIRE TO THE METAL otherwise this thing produces little heat and is useless.
3 x flower pots of different sizes
1 x piece threaded rod -mine six inches
some pop can bottoms
a piece of metal
some stainless steel wool
some aluminum strips
some bike wheel spokes
some 14 gauge copper wire
some 1/2 inch copper pipe
a piece of plywood
a metal tin can lid, you can use other metal or aluminum here
drill bits as needed
screw drivers as needed
1. SAFETY SAFETY SAFETY SAFETY and more SAFETY
The shinny stuff on the rod, the nuts and washers is galvanizing, to prevent rusting. It is BAD for you when heated. Before building one of these you MUST burn the shinny stuff off, use stainless steel or welding iron.Burn by creating a fire put the pieces in the fire and step away from the fire. Do this outside in ventilated space.See pictures. After the burn clean the metal with wire brush, wear a NOSH N95 mask.
Four pictures 1-shinny, 2-the burn, 3-after the burn, 4-after cleaning
2. The Build
a - The build of the heater differentiates from others in that I used a large metal plate at the bottom where the flame touches the metal, followed by a piece of 1/2 copper pipe, then followed by two pop can bottoms, followed by another piece of pipe, three more can bottoms. The small pot with five holes goes over the fins, one can bottom, the medium pot with 4 holes goes over small pot, one more can bottom followed by the large pot, a can bottom, washer and nut. The can bottoms afforded me the ability to finger tighten the assembly. After the initial assembly I applied heat to the unit with a heat gun. Result in picture 6
b - Stand and final assembly
The stand consists of a piece of plywood followed by a tin can lid, four aluminum strips for legs, and five bicycle tire spokes. Steel wool was placed in the gap between the small and medium pots.The steel wool helps with the transfer of heat.
3. Temperature Measurement
The temperature measurements were conducted in a outside kitchen / mud room.The outside temperature was -3Celcius, the temperature in the room was 6 Celsius as indicated by the analogue thermometer,
The temperature measurements lasted for an hour starting at 6:29AM to 7:35AM.
Used two oven thermometers and one infrared. One oven thermometer was used to measure the core temperature through a hole drilled through the external middle pots.The infrared was used at random to measure the temperature of the outer pot. At the end of the measurements I switched to the second oven thermometer to verify the outside pot temperature. As I could not attach the probe to the pot directly it was held in place by me resulting in a reading of 81 C, the infrared read 96 C, the core temperature read 206 C. Averaging the temperature of the infrared and oven thermometer on the outside pot is 88.5 C.
In conclusion, as shown by the temperature measurements the results show that this can be used to generate significant heat as long as the flame is applied to the metal. I built this using what was available to me. I had to go to several stores to get the pots and was able to get only these, The biggest 6 inches, the smallest 3,5 inches. It is out of season in most stores. I will be needing a couple of these in bigger format to warm my tunnel greenhouses next year and will be looking for bigger pots in flea markets. Will also investigate using candles in Crisco to extend the burning time of the candles. For those heaters i will use heavier metal for the bottom plate as well as thicker aluminum for the fins.
Some of you may ask where is the thermal reactor. Fire heats metal plate, heat radiates from metal plate to rod and fins and then outwards to the pots. It is I believe a thermal dynamics reaction.