All electric flat - immersion water timers

Jay_c_2

Thanks alot for all of your responses. I had another look yesterday, now I have two timers on the wall. I automatically assumed top was top heater bottom was bottom, now I am not sure as there are no wires leading into the heater so I cant tell.
After no success with the bottom timer, I switched on the top one, from cold it has gone to full temperature in 4 hours could I just have been getting the timers mixed up and that the timer underneath is for added boost?