Pictured below is a modified version of our standard Surplus Solar PV Immersion Controller a device designed to use electricity generated by photovoltaic solar panels to power a water heating immersion element rather than exporting the electricity to the grid.
This version works identically to the standard unit, the only difference is that instead of having a mains switching relay on the circuit board itself, there is a 12VDC output when then solar generation is above the user-set threshold which can be used to control a solid state relay or other relay in situations where the 16A relay we usually supply would not be up to the job – e.g. for a very large immersion element.
Pictured above for example is a 25A rated SSR (solid state relay). The 12VDC output from our controller connects to the terminals labelled 3 (+) and 4 (-), and then the mains live cable is switched through terminals 1 and 2.