8 hours run time for variable speed pumps -- at what rpm?

[szmad]

I read the post "determining pump run time," which recommends 8 hours of run time if your pump is capable of running on lower speeds. I have a variable speed pump that goes from 800 rpm to over 3000 rpm, as follows:

800 rpm 105 W 10 gpm
1200 rpm 175 W 25 gpm
1600 rpm 315 W 60 gpm
2050 rpm 490 W 80 gpm
3000 rpm 1700 W

where gpm is gallons per minute.

Right now I'm running 18 hours at 1200 rpm and 6 hours at 1600, and everything is fine, but I think I'm overdoing it. On the other hand, I suspect that 8 hours at the lowest speed, 800 rpm, won't cut it. (For perspective, I estimate that would provide 0.4 pool turnovers [I know the aforementioned post doesn't use a turnover rule of thumb, but this is just for some perspective].) If I run 1200 rpm for 8 hours in the middle of the day I get one full turnover, for $11/month total cost (based on weighted average TOU electricity prices). I have an alternate plan that varies between 800 and 1450 rpm for 14 hours and provides 2 turnovers for $18/month. I sweep and skim just about daily, and keep the pool covered 75% of the time.

Pump motor/seal life also is an issue, but my own general knowledge and what I've read here suggest that motor calendar life cannot be related in any simple way to hours run time per day.

Any comments appreciated.

 

[needsajet]

Whatever speed works to achieve circulation needs and skimming under average to favorable conditions. Try 1500 and see how it goes. Adjust from there. If you want skimming to be perfect under unfavorable conditions, crank it up.

If there are any components with minimum flow requirements, such as SWG, heater, etc. then those flow rates must be met.

Duration you can tell from the clarity of the water. Run it as long as it takes to meet your standard for water clarity. Your FC feeder may need a minimum duration.

Good luck with the tuning!

 

[szmad]

Thanks needsajet. I don't have a SWG or a heater, and I can adjust the flow on my cl feeder as needed (right now it's at 1.5 out of 6 running 24/7, so assuming the feeder scale is cardinal in mathematical terms, I can cut down to 6 hours and still get adequate cl from the feeder). So it looks like it is trial-and-error tuning. My sense now is that 800 rpm is just too low, even 24/7; 1200 rpm 24/7 is fine (crystal-clear water), but probably not necessary. I'm thinking of either 1500 rpm for 7 hours, mid-day, or 1200 rpm for 14 hours, daytime. Both give the same pool turnover (again, just using this for perspective), but 1200/14 is $2/month more.

 

[needsajet]

I run mine 8-11 hrs at 200 watts, ~25 gpm, in summer