Supplemental Heat for a Solar Kiln
From Gene Wengert, forum technical advisor:
To the original questioner: You need a different type of heater; propane is often used. You also must be careful that you do not over-heat and cause a fire. Hence, use plenty of safety devices. A double layer on the clear roof will really help the heating.
Contributor A - Did you add this heat from a few light bulbs in a solar kiln? The heat losses are typically so large in a solar kiln that you need a huge amount of power.
From contributor R:
A non-thermostatically controlled kerosene jet heater and a thermostat from a hot water heater will give you lot of heat that is easy to control.
From the original questioner:
I thought about propane, but thought that might add moisture into the lumber. I may look into that but I will add the second layer for sure and see how much that will raise the temp.
From contributor A:
No, my kiln is not solar. It is a small 500 BF DH kiln with electric supplementary heat. I added the heat to get above 130F to kill PPB's at the very end of the cycle.
From contributor C:
I used emergency heat strips out of an air handler from a home AC system. You must have a fan blowing over the heat strips to keep them from glowing and burning in two. I heat my kiln to 160 degrees. The air handler will also have the appropriate safety cutout switches, thermal fuses, 24 volt transformer, contactors, etc. You can get a digital programmable thermostat for about $35. Check with industrial suppliers and refrigeration suppliers.
The fan motor is a different story. I had to run the squirrel cage fan by belt and put the motor outside the kiln away from the heat to keep it from overheating and shutting off because of the thermal protection in the motor.
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