New pump choice-- 2 speed or variable

[gworrel]

I believe I am spending too much money running my current pump. I am trying to decide if it is worth spending the money for an Intelliflo Variable Speed pump versus a 2 speed. I have looked at the Pentair site calculator which projects a savings of $334 or more a year compared to what I have now. Their calculator is based on CEC curve C which I don't think is a good match for my equipment. I just don't know if I would save less or more. http://www.pentairpool.com/pool-owner/r ... /index.htm. It is also not clear what assumptions they are making about the 2 speed pump option

My pool and current equipment:

21000 gallons in-ground gunite. Separate 700 gallon Teak Hot tub that uses same pump, filter, and heater. The hot tub has 4 jets.

Equipment is all in garage, with pump about 20 feet from Hot tub and 60 feet from pool skimmer. Return line to pool is about 20 feet from pump. All pipes outside of garage are 1.5". Inside garage all pipe and connections are upgraded to 2". Pool water level is about 12" above pump. Hot tub water line is about 36" above pump.

Aqualogic P4 controller with salt water chlorinator, 2 electric 3 way valves to direct water to/from pool and hot tub.

Raypak RP2100 natural gas heater

Sta-Rite Dura-glas pump P2R 5F-1251 with Century 1.5 HP motor, B842. SF 1.47. 9.6-8.8 amps. The original motor that came with the pump was a 1 HP and when it needed replacing I put on the 1.5 HP. I realize now that was probably a mistake. At least it is an energy efficient motor design.

Waterway Eliminator 570-048 DE filter 48 sq ft.

Praher SM20-1 2" multiport valve (max drop 5.5psi @95gpm)

2" Jandy check valve in suction line to prevent hot tub from draining into pool while valves are switching.

I have not yet opened the pool for the year but I believe the clean filter psi reading was about 15.

My electric rate is 13.5c /kwh but with taxes and surcharges, 15.7c.

There are lots of variables in the Pentair calculator. I think I was running the pump about 12 hours a day last year. That probably wasn't necessary but I have trees in the vicinity so debris is a problem. I would like to run it even more if I could run it on a low speed and get some skimming action. The Pentair calculator says I would save $499 with the Intelliflo and $365 with a 2 speed pump running 12 hours a day. It looks like I can get a good 2 speed 1HP pump (Pentair Superflo or Hayward Super Pump) for about $400-450. The Intelliflo is at least about $840 and $160 more for the automation interface to the Aqua Logic. Am I missing anything? Thanks for any help.

Greg

 

[JasonLion]

Using an oversized motor on your existing pump is fine. The electrical usage will actually be just slightly lower than it was for the original motor. The amount of water moved and thus the electrical usage is mostly a function of the impeller, which you didn't change.

The Pentair pump cost calculator makes a number of assumptions that don't always apply. In most cases it ends up giving somewhat optimistic estimates of how much electricity you can save.

With electricity around $0.16/kwh chances are you will save the most money by getting a two speed pump.

 

[gworrel]

Thanks Jason.

I like the flexibility of the Intelliflo. I am afraid that if the low speed of the 2 speed pump is too low to get good skimming then I will not want to use it all the time. The Intelliflo gives the option to bump up the speed a bit or run even lower speed for a longer time if it still works for skimming. It would still be nice to know that the price difference will pay off. I wonder if anyone has tried controlling the Intelliflo with the instructions given here:
http://technicalpoolrepair.blogspot.com ... h-and.html

 

[PSW]

I am afraid that if the low speed of the 2 speed pump is too low to get good skimming then I will not want to use it all the time.

The low speed on a 2-speed pump will be 1/4 hp. Typically, this is plenty to get good circulation and skimming..as long as you optimize the directions of your returns. To test the surface movement, you can toss a ping pong ball into the pool and watch it float around the surface!