Our system was installed in the sixties and has a detailed time clock which i never really understood with night and day settings etc. We just switched on the heating when required and then manually switched it off when no longer needed. If the system would not come on we pressed a red button which overrided the clock..dont know if this is the correct term. My query is whether one can permanently disable the clock and just switch on and off when required. I am pretty ignorant re these matters