Added a second SSR to turn on and off the lower water heater element as needed. The lower element was burned out but we only noticed when we had company and more hot water was needed. 

Only using the upper element and only heating the upper 1/3 of the tank is enough hot water for the two of us normally. The unheated lower part acts as a tempering tank, especially in winter when the incoming water is only 9C. It gains a few degrees just sitting in the basement which is a few degrees less that that upper element needs to heat.

The new lower element only turns on after the upper thermostat setpoint is reached and the upper element is off. The lower element is now enabled from the web page only when more hot water is needed in order to save energy and dollars.