Hi James I have the chlorine dispenser with a couple of tablets and number 2 with the pump running 6 hrs a day
The tabs in the feeder continue to dissolve and this creates a corrosive soup of chlorine gas and acid that can/will migrate through the system and damage all equipment when the pump is off.
I was questioning why the heater cycles for1min every 20 min may be to check temperature not sure
Seems like an error condition like excessive refrigerant pressure causing a safety sensor trip.
Maybe get an HVAC tech to check everything.
It can be difficult and expensive to find qualified HVAC techs who are ready, willing and able to work on pool heat pumps.
Based on the age, I would not spend a lot of money on the heat pump.
It is a gamble every time you spend money because it might make the heat pump work correctly and it might not, which just wastes your money.
At some point, it makes more sense to replace it with a new heater.
Have the new heat pump installed by an HVAC company who will agree to warranty and service the heat pump as needed.
Pool companies are not qualified to work on heat pumps except for simple repairs not involving refrigerant.