I also split my run time. I do three hours at dusk primarily so I can be up and around when the filter turns on to make sure all is well with the pump, filter, SWCG etc. this also replenishes part of the chlorine lost during the day. The system turns on again at 4:00 a.m. for another 3-4 hours for two reasons. A) it is cooler in the morning for running the pump motor. B) all the chlorine is generated during the night (or early morning) . That way the full amount of chlorine is present to sanitize the pool before too much sun hits the pool and starts the burn off.