Variable Speed Pumps

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jblizzle said:
That does not make any sense ... with lower flow rates, the bubbles would have more time to "dissolve" in the water before entering the pool and escaping to the atmosphere.
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This was my first day running my vsp pump, 2 hrs at 3400 rpm, then 1400 the rest. I tested the FC in the morning it was 8.5 at the end of the day it was 10, running 11 hrs. Well I guess I need to do some tweaking, my target is 8..I think what you are saying seems to be correct.

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Jason, at high flow rates I don't see any bubbles at all. Maybe there are no bubbles or the bubbles are so small I can't see them.

A possible explanation is that higher, more turbulent flow produces smaller bubbles at the cell, and small bubbles dissolve much faster than large bubbles.
 
My swg works just fine @1000 rpm. It may work better @ 1500 rpm but DSP says no difference. The installer said my Polaris will work at 1000rpm too, but I haven't checked that out either. But definitely, the skimmers work better @ 1500rpm. Love my vs pump!
 
I'm running at 1500rpm from 8am-8 pm then 1000rpm from 8pm-7am. I'm running My swg @ 80% but need to dial that down since my fc has pretty much stabilized @ 14ppm. I might disable that over night run. Then see what I can do to Stabilize my fc @ ~7 my water temp has gone down quite a bit lately.
 
2-speed pumps will give the bulk of the benefit but there are two situations where a variable-speed pump gives benefits not available in a 2-speed pump.

First is that one can tune the variable-speed specifically so can tweak out additional savings at high speeds. In my own pool I used to have a single-speed 1 HP full-rated (1.65 SF) Jandy HHP pump which when used with my solar system was running at around 55 GPM at 3450 RPM and consumed 1800 Watts. The Pentair Intelliflo VF that I used to replace it would actually be less efficient if run at the same speed and would be around 2100 Watts, but I lowered the speed to 4 GPM per panel (12 of them) for 48 GPM at 3000 RPM that consumes 1500 Watts, so a savings of 300 Watts.

When the solar is off, I run at 26 GPM at 1500 RPM and consume 275 Watts. With a 2-speed pump running at low-speed 1725 RPM it would be higher energy usage, perhaps 400 Watts (22% of 1800W). Also, this may be at 29 GPM which is on the edge of what is required if I want to run my gas heater which has a minimum flow rate at 30 GPM and even then the higher temperature in the heater can wear it out faster so 40 GPM might be preferable. With my VF with the gas heater I run at 40 GPM at 2075 RPM and consume 615 Watts.

Finally, I was also able to get rid of my 0.75 HP booster pump at 1400 Watts for my pressure-side cleaner and instead use The Pool Cleaner with my Intelliflo VF set to 15 GPM and 540 Watts. I couldn't do this with a 2-speed pump without using a valve for partial flow and I found using such valves were not very reliable at providing consistent flow. So instead, my VF is used with a valve that switches completely over to the dedicated line to the pressure-side cleaner.

My overall savings cut my pump electricity costs roughly in half from $1500 to $700 (today it's more like $1700 to $750 given even higher marginal electricity rates of 40 cents per KWh).

A 2-speed pump would give me the majority of the savings, but not as much.
 
boston62, timerguy, I din't think you can directly compare rpm even if you have the same pump. After reading Mark's terrific posts in Hyraulics 101 I understand the gpm put out by your pump will vary considerably depending upon the head it's pumping against. To find out the gpm your pump puts out you first have to calibrate it, and the easiest way to calibrate is to run it at 3450 rpm and note the watts. You then compare this to data available from CEC or APSP for your specific model.

For example the CEC data for my pump at 3450 rpm is:

1990 watts, 43 gpm
2340 watts, 71 gpm
2720 watts, 97 gpm

So the lower the watts, the lower the flow, and the variance can be huge depending on the head loss in your system.

My pump draws 2866 watts at 3450 rpm so I figure its pumping about 106 gpm. If I understood Mark's posts correctly, the gpm at any other speed is directly proportional to rpm, so for me the gpm at 1500 rpm would be 106*1500/3450 = 46 gpm. but for you guys it could be way different depending upon your plumbing.

It's really interesting to run the pump at different speeds, note the watts and then calculate the watts/gpm for your pump and your system. My pump goes from 4.2 watts/gpm at 800 rpm, up to 27 watts/gpm at 3450.

I guess another advantage of VS pumps is they generate enough information to keep geeks interested and out of other mischief. :D
 
An easier way to dial in your rpm settings is adding a flow meter. I bought one for about $35 and added it to my system. Now I can see the difference when the solar is on, and can adjust my pump setting for various tasks.
 

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should i cut down run time?
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You can cut back run time as much as you want but you should probably have at least 2 hours per day for circulation. The rest of the time is just for skimming and bottom cleaning if you have an automatic cleaner.
 
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