Estimating power use from variable speed pump on pool pop-up

[pfp]

First a little background...
I'm looking to add a grid tied solar system to the house that provides 100% of my yearly kWh use. This has nothing to do with the pool except that the solar array needs to be sized to account for whatever power the pool equipment uses.

The pool is small, approx 10,000 gallons, sand filter, salt generator, and in floor pop-up cleaning. The current pump is 1hp (3450rpm) which I've calculated to use about 1.9kWh (This roughly matches the hourly utility usage data). The pump runs for approx 5 hours per day which puts the annual power use at around 3600 kWh. Thats a rather large amount of power and by reducing it I can save money on the solar system by reducing it's size.

I'm looking at either the Intelliflo or Ecostar variable speed pumps which both appear to use far less electricty. From what I've been able to gather running either of these pumps at 1000 - 1500 should be enough for everything but the in floor cleaning and at those speeds would save a significant amount of power even if run all day long. I'm assuming that both the Pentair and Hayward power calculators use these low speeds in their calculations.

The piece I'm unsure of is how fast the pump will need to go for the in floor cleaning to operate and how much electricity would be used at that speed. Also I'm not sure how long the in floor cleaning needs to be run each day?

I'm currently guessing with 2 hours of infloor cleaning at 2720 watts (not sure why this would be higher than my current pump though) + 10 hours filtering at 200 watts. This leaves me at roughtly 7.5kWh per day which only about 13% less than the currnet 9.5kWh. Does this sound even remotely close?

 

[mas985]

Re: Estimating power use from variable speed pump on pool po

If your current pump is working well for the in-floor system, with a VS, it might have a little bit lower energy consumption at the same flow but to be safe, assume the same 1.9 kw.

Lower speed run time is dependent upon how much extra run time you will actually need. Just keep in mind that the skimmers and cleaners do not work as well on lower speeds as higher speeds.

Also, there have been studies done in Florida which suggest that a typical pool may be able to get away with as little as four hours per day in pump run time, independent of flow rate. So you may actually need very little low speed run time. It depends more on how much stuff is falling in the pool and how well skimming works on low speed. If skimming does not work well on low speed or you use a solar cover most of the time, then the only reason to run on low speed is to add chlorine.

Often times when I look at the lifetime cost of a VS vs a two speed pump, I find that the two speed has a much lower lifetime cost because of these factors. My main point is don't automatically assume that a VS is going to save you a ton of money, there are many other factors which determine the cost of running a pump. How you setup the run time is the biggest factor of all.

 

[pfp]

Re: Estimating power use from variable speed pump on pool po

I read somewhere that there is a maximum limit on GPM through any size pipe. I've seen different sources stating that this limit is either 73 or 80 for a 2" pipe. Is this correct? A diagram of my plumbing is shown below and all main pipe is 2", the water feature which is normally off is 2", the skimmer return is 1.5", the aerator which is also always off is .75". What is not shown in the diagram is the spider like thing where all the piping for the infloor cleaning goes out. based on this mean would my max GPM be 80?

This next chart is from Hayward for the ecostar pump. If my plumbing is limited to 80 gpm then there would be no reason to run the pump at 2450rpm unless my head was 80, correct?

If that's the case then I need to figure out the head for my pool to determine that max speed that I would ever need to run the pump? Without any specialized tools or know how is it possible to make a reasonable estimate of this?

Thank you

 

[mas985]

Re: Estimating power use from variable speed pump on pool po

I read somewhere that there is a maximum limit on GPM through any size pipe.

Not true. I cover the issue in the Hydraulics 101 sticky. I also have flow rate estimates for the Ecostar.

If that's the case then I need to figure out the head for my pool to determine that max speed that I would ever need to run the pump? Without any specialized tools or know how is it possible to make a reasonable estimate of this?

It is hard to do without the tools but luckily I have them. In any case, as I pointed out in the sticky, there really is no limit to flow rate in a pipe. Only recommendations.