PoolPilot states that if you want to use the digital section to control pH the CyA has to be kept at between 30 and 50 ppm. If you want to keep the CyA in the 70 to 80 range it cannot be used.
Assuming a target Chlorine level of 8 (yellow algae/mustard gas issues in our area), the Power Level was just moved to 3 and at 82F it is running at 70% to acheive this level over a 5 hour period. This seems to be the minimum hours to acheive a Chlorine level of 8 without much fluctuation.
It was at Level 2 at around 93% to 97% but PoolPilot states it would be better for the SC60 cell to run it at a higher level (Level 3) and a percentage no higher than 75%. If the CyA was lowered to 50 it might be possible to acheive a Chlorine reading of 8 ppm, but then the pump would need to run for longer. As the KwH is around 35 cents in Honolulu it would start to get very expensive. At present in 5 hours it compensates for around a 3 ppm daily loss of chlorine.
The digital section is presently turned off and it doses a constant 2-3 oz of acid daily, adjusted back and forward every 4 days.
If the CYA level was at 50 ppm then would it be correct to assume the pump hours would have to increased considerably?
A second question for interest's sake, what is the daily loss percentage of Chlorine at a CyA of at 50 ppm and the loss at say 80 ppm?
The reason the CyA is kept in the 70 to 80 range is that it seems to cut down on acid usage considerably and the alkalinity stays at a constant 90, it never seems to move, I do not know why. When the CyA was kept at 35 both the usage of acid to control the pH and baking soda to control the alkalinity were very high. I suppose one "Cannot Have The Cake And Eat It To" at least in this case, with our soft Hawaiian water, whose pH is around 8.2 out of the tap.
Presumably areas with more acidic water might not have these issues.