Dual speed pump hydraulics

[DrZach]

How can you tell from these pump head curves that are provided for these dual speed pumps what the flow rates are at the low Vs high speeds?
I have searched everywhere and cannot find any info to tell the flow difference between these two pumps for the low and high speed or any head curves that looks like one that I would expect for a dual flow.

My system is fairly simple, 1.5" flex hose pipe AG pool with single inline skimmer to pump sitting on the groung to filter back to pool (not sure what head loss that I should expect)

Here are the pumps I am trying to look at

Pentair Dynamo Pump 1 HP 2 Spd. (no cord) - 340204 - INYOPools.com

Pentair Dynamo Pump 1 HP 2 Spd. (no cord) - 340204 - INYOPools.com


Thanks!

 

[jblizzle]

Determining the flow rate is non-trivial because you need to know the head loss in your system. Mark has a spreadsheet that can estimated given some of your pool parameters, but there is really no need to know the flow rate generally.

To compare two pumps, just pick a head loss and compare the flow rates between the two pumps at that head loss.

 

[CJadamec]

In general you will get about 1/3-1/2 the flow on low speed as you get on high speed depending on the amount of head your pump is running at. You have no equipment that is flow rate dependent to operate so the low speed flow rate doesn't matter. You will still get good skimming action on low and it will be more than enough to circulate the water in your pool.

As I said before the 1.5hp and 1hp dynamo pumps have identical flow charts so that tells me its the same pump and motor but they have pulled a marketing trick and made the 1.5hp pump "sound" more powerful by playing with the service rating of the electrical motor. We Americans always think more power is better and will pay more money for more power. Pool pump marketers take advantage of that and trick you into buying the more HP for more money when you are really just buying the same pump but in a fancier box.

 

[DrZach]

I agree entirely with you given the hydraulics article read, where I got lost was the company put the same head curve for both pumps (even though they draw different amperage) so I'm not sure how to compare the two.
Where is that other resource?

 

[JohnFoe]

How can you tell from these pump head curves that are provided for these dual speed pumps what the flow rates are at the low Vs high speeds?
I have searched everywhere and cannot find any info to tell the flow difference between these two pumps for the low and high speed or any head curves that looks like one that I would expect for a dual flow.

My system is fairly simple, 1.5" flex hose pipe AG pool with single inline skimmer to pump sitting on the groung to filter back to pool (not sure what head loss that I should expect)

Here are the pumps I am trying to look at

Pentair Dynamo Pump 1 HP 2 Spd. (no cord) - 340204 - INYOPools.com

Pentair Dynamo Pump 1 HP 2 Spd. (no cord) - 340204 - INYOPools.com


Thanks!

I just installed this same exact pump from inyopools.com today.

If you have a simple setup, just assume 25 foot of head loss.

I don't know the GPM on the low speed, but I'm estimating I get 35 GPM on low. There is significant flow, but high pressure definitely "feels" the same as the 1.5HP version of the same pump I replaced. It might be less, but it can't be much less.

I wish I could give you more information. I asked inyopools.com and they didn't know the GPM on the low setting. They recommended me to call the manufacture.

A basic rule is half of the high setting, but I don't have the tools to actually measure it.