My setup currently
Hayward sand filter, 1.5hp pump, analog timer, Teledyne Laars Heater.
The heater has no electronics, it operates based on pressure. When the pressure increases the heater functions, when the pressure drops the heater turns off. Thus (I assumed) the timer for the filter controls the filtering times, and when the filter shuts off automatically so does the heater.
The heater has a Warning label which tells me the heater must be shutoff 20 minutes before the pump is shut off. - THEY MEAN IT!. I accidentally went to breakfast with the system on, and didn't realize the timer was about to turn off. I returned home to find the CPVC Plumbing (on the input side) has begun to melt and was spraying water.
SO now I know there is no latitude here, the heater MUST be off long before the pump stops circulating the water. But how can this be accomplished when I am not home and the system is run automatically?
I know that there is newer equipment with digital control of everything, but I have to believe that even though my system is older, it had to have worked at one time using the system the way it was originally designed. There is no conection for an auxiliary timer for the heater, there is no power to the heater to control. The heater has an on off switch, and a min/max dial for temp.
I guess this boils "pun" down to - How were these heaters originally intended to be setup and run, Mine did not come with instructions of any type.
I'll be out in the yard repairing my plumbing while I await your suggestions