Q: I have a Pentair IC-40 5200 gallon pool, how many hours and what percentage should it run ?
Answer:
If you have an IC-40 on a 5200 gallon pool that is super oversized. I’d only run the chlorinator on the lowest setting for one hour a day because an IC40 can sanitize 40,000 gallons of water every 24 hour period, so you are only looking for about 1/8th of that.
They do make smaller cells, IC20 would even be 4x what you need (unless you mis-typed the gallons?)
So less in this case will be best.