Flow Rate w/ Variable Speed Pump

[addds]

My PB set up a schedule for my pump to run 24/7. 16 hours at 60% and 8 hours at 100%.

1) is that necessary?

My filter capacity is 150gpm max. This theoretically turns over my pool in 3 hours.

2) can I assume that 60% pump speed is directly proportional to filtration rate? In other words, 150 gpm at 60%= 90 gpm. My basic knowledge of fluid dynamics says no.

 

[Texas Splash]

1 - No. Water turnover is a generic term some people use and not relevant here at TFP. You only need to move water long enough to skim the water's surface, mix chemicals, and support equipment (i.e. SWG, heater, etc). Now if you wish to run the pump 24/7 at a very low rpm (i.e. 1,200 - 1,400), that's fine. Many people do that.

2 - As long as you have adequate water flow for your SWG cell (flow switch), it's fine. I bet you could lower the rpm to around 1,400 and be just fine. Then only increase the rpm for cleaning, the waterfall, or to purge air once or twice a day from the pump pot.

 

[Jimrahbe]

A,

In most cases there is no need to run the pump faster than what will turn on your SWCG.

Not sure what that speed would be, as you have heater and other "stuff" in the water's path. You will just have to turn the speed down until the salt cell shows low flow and then turn it back up until the flow switch closes, and then just a little more.

The whole point of having a VS pump is to run as slow as you can to save on the electrical bill.

I personally love running 24/7 as it means I'm making a little chlorine all the time, and skimming all the time. I also like the look of the pool when there is a little water movement. That said, I do not have a heater, so I'm running at about 1200 RPM most of the time. Running 24/7 costs me less than $20 bucks a month.

Thanks,

Jim R.

 

[addds]

Thanks Jim and Texas!

I'm still new. When you say the SWG flow switch, do you mean what's in the picture?

How do I know its on and generating? My system measures ORP, which is still confusing to me.

Finally, my system runs on % of max speed, not rpms.

 

[Jimrahbe]

A,

% of max speed or RPMs it does not really matter. The basic concept is to run the pump as slow as possible and still get the job done.

You salt system has to have a certain amount of water flow through the cell for it to work. The salt system has a flow switch that closes when the right amount of water is flowing through the cell. On my system there is a light on the cell.. I suspect that your system has a flow light on the control panel somewhere.

The TFP pool care process does not work well with ORP control.. This is because you have to keep your CYA level very low.

Your pics is of a device to measure the water flow through the system. Not something that you need to even look at for now...

The Sense and Dispense system is sold as a system that automatically runs the pool for you. But like all fully automated systems it only works right up to the point of the crash.

Thanks,

Jim R.

 

[JamesW]

The maximum speed is 3,450 rpm, so you can convert from percentage to rpm by multiplying the percentage by 3,450 or you can change the reading from percentage to rpm in the settings.

How do you like the Pentair whisperflo XF 5.0 HP water features pump?

 

[HermanTX]

Thanks Jim and Texas!

I'm still new. When you say the SWG flow switch, do you mean what's in the picture?

How do I know its on and generating? My system measures ORP, which is still confusing to me.

Finally, my system runs on % of max speed, not rpms.

I have one of those same flow meters. I put it in just to see what my GPM was through my equipment.

I run my pump for 19 hours at about 25gpm (according to the flow meter) which is about 1500rpm for my pump and plumbing set up. The rest of the day it runs at a higher speed (about 40gpm on the flow meter) for skimming action. You can turn your pump much lower which will save you a lot of energy costs and still operate your SWCG to produce chlorine. So you might wish to try 40% for 18 hrs and 60% for 6 hrs. That is just a starting point and you can adjust from there that works best for you. There is no need to run a VS pump at 100% (unless it is priming which is for about 2 minutes)

My highest flow rate is when I use the heater which gets to about 60gpm. Other than that, the pump runs low speed (low gpm), quiet and very energy efficient and allows the SWCG to produce chlorine all day.

 

[addds]

A,

% of max speed or RPMs it does not really matter. The basic concept is to run the pump as slow as possible and still get the job done.

You salt system has to have a certain amount of water flow through the cell for it to work. The salt system has a flow switch that closes when the right amount of water is flowing through the cell. On my system there is a light on the cell.. I suspect that your system has a flow light on the control panel somewhere.

The TFP pool care process does not work well with ORP control.. This is because you have to keep your CYA level very low.

Your pics is of a device to measure the water flow through the system. Not something that you need to even look at for now...

The Sense and Dispense system is sold as a system that automatically runs the pool for you. But like all fully automated systems it only works right up to the point of the crash.

Thanks,

Jim R.

Do you have any recommendations on where to go to learn more on how to operate this system? Or is there a way to bypass or replace it?

 

[addds]

The maximum speed is 3,450 rpm, so you can convert from percentage to rpm by multiplying the percentage by 3,450 or you can change the reading from percentage to rpm in the settings.

How do you like the Pentair whisperflo XF 5.0 HP water features pump?

It is efficient, responsive and powers both 8 foot sheet- style water falls very well.

My equipment is about 50 feet from the pool and around the corner of the house. This pump is loud.

 

[Jimrahbe]

A,

VS pumps are just as loud when run at close to full speed, as any single speed pump...

One of the great things about a VS pump is that when run at a low speed they are very quiet. When I initially installed my 3 HP IntelliFlo pump, I actually had to touch the pump just to make sure it was running... I run mostly at 1200 RPM, and at that speed you can't hear the pump at all unless you really listen. The pump is about 5 feet from my the headboard of my bed, and in the 10 years that I have owned it, I have never heard it running from inside the house.

You obviously will need to run your pump at a pretty good clip to power an 8' sheer waterfall.. But, I assume your waterfall does not constantly run.

I don't know enough about your Sense and Dispense system to be able to provide you with any reliable help.. Even though I am not a fan of these types of systems in general, I would not recommend that you abandon it just yet. I would try to use it as is, and see how well it works for you. If all is well, great!! If not, we can go from there.

Show us several pics of your equipment pad and the S&D system, so we can see what you have.. Maybe we can come up with some better ideas.

Thanks,

Jim R.

 

[JamesW]

It is efficient, responsive and powers both 8 foot sheet- style water falls very well.

My equipment is about 50 feet from the pool and around the corner of the house. This pump is loud.

What speed do you run the pump?

How much flow is required for the water features?

Pumps are loud at RPMs above about 2,500 RPM, but there can be reasons for excessive noise like cavitation if the suction lines are too small.

If the suction side head loss is greater than about 17 feet, then that can put the pump at risk of cavitating.

For the 5 hp commercial WhisperFlo XF, the minimum suction pipe size should probably be about 4".

For 16 feet of sheers, you need about 200 GPM (16 foot at 12.5 GPM/Foot) for good projection.

If the lines are sized correctly, then the pump should be able to provide 200 GPM at 3,000 RPM or slightly lower.

Pipe Size and Flow Rates.​

You want to keep the water velocity below 6 ft/sec on the suction and below 8 ft/sec on the pressure side of the pump.

Pipe Size	6 ft/sec	8 ft/sec
1.5"	38 GPM	51 GPM
2"	63 GPM	84 GPM
2.5	90 GPM	119 GPM
3.0"	138 GPM	184 GPM
4.0"	235 GPM	312 GPM

https://www.bestbuypoolsupply.com/media/sheerdescentinstall.pdf

Note: NPSHr (Net Positive Suction Head Required) is the minimum pressure at the suction port of the pump to keep the pump from cavitating.

The NPSHa (Net Positive Suction Head Available) is 34 - head loss at sea level.

At 200 GPM, the NPSHr is 20 feet, so the NPSHa has to be higher than 20 feet, which means that the head loss has to be below 14 feet (34 - 14 = 20).

For a 3" pipe (100 feet total equivalent length) the head loss is about 7.9 feet (Dynamic).

You also have to add the static head loss, which is the height of the pump inlet above the surface of the water.

To avoid cavitation at 200 gpm and 3" pipe, the pump cannot be higher than 6.1 feet above the water.

 

[JamesW]

For 180 GPM (11.25 GPM/Foot), you would need about 2,500 RPM assuming the plumbing was sized correctly.

For 200 GPM (12.5 GPM/Foot), you would need about 2,750 RPM assuming the plumbing was sized correctly.

The range of sheer flow per foot is about 7 GPM/Foot to 20 GPM per foot with 10 to 12 GPM per foot being the average flow for average performance.