I went through six different methods to heat the silica beads when they needed to be recharged. They all failed to reach to 60°C (140°F) temperature needed to recharge the beads, even though each method on paper looked promising – well the fish tank heater was too hot and would shutdown due to overheating so technically it was hot enough. After some head scratching, using high wattage resistors popped into my head. I found a chart to convert heat generated for a given amount of power running through a resistor. Some math narrowed down size of resistors I would need and soon enough parts were on order. Even with the math there was some trial and error to narrow down the best combination. The first version assembled I used three 330 ohm resisters in series, which were put in parallel with a second set of three 330 ohm resisters in series (effectively two individual 990 ohm resistors each connected to 120VAC). My current version uses the nine resistors (3 sets of 3 resistors in series, which are parallel with each set) in the 25W metal case that are screwed to a 1-1/4″ flat bar – a huge improvement to distributing the heat and improved safety
Fix methods of to recharge the silica beads were attempted:
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