I am working on a arduino based solar hot water system. One little side project is to determine whether the hot water I am getting is heated solely by solar, or whether the Bosch Aquastar tankless hot water heater has turned on to boost the temperature.
My first thought was to use a CdS light sensor, appropriately placed to see the light of the gas flame. The readings I am getting are too widely fluctuating to work based just on a threshold value.
Anyone have any ideas for a better way to determine whether the heater has kicked in?
Thank You Kindly,