Kelly, I have used a 1500 watt waterheater element, inserted into a waterjackte of a 1" pipe through a "T" allowing the selfsiphon action to rise and return to the holding tank.. powered by two Photowatt 1000 24V panels on a Tace C 40, the amount of heat output is disappointing, it is fine for the load dump but would rather have more use of the power. I am thinking of using an old toaster next to see if it will provide more usable heat. At least I can shorten the wires to find an optimum result. Using the toaster with a computer fan for circulation, perhaps a daylight space heater, It is all an experiment.
