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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7919
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have just had a Hayward EcoStar SP3400VSP pump installed

Resolved Question:

I have just had a Hayward EcoStar SP3400VSP pump installed in my pool. I'm in the process of programing the settings.

The suction pipe is 3". According to the manual, max flow rate with 3" pipes is 160 GPM. I assume that flow rate occurs when the pump is operating at Max. speed of 3450 rpm. According to my calculations, that would turn over 57,600 gallons in 6 hours. My pool is a 20,000 gallon pool.

I prefer to run the pump at lower rpms, and need to be able to calculate the number of hours necessary to turnover my pool at a selected lower rpm. Can you email a table (or website) indicating GPM at different rpm's for this model pump with a 3" suction pipe?
Submitted: 5 years ago.
Category: HVAC
Expert:  Phil replied 5 years ago.

Phil :

Hi,This is risky business, not responsible for damages on your end. We *keep going until *you are happy. I come and go. be patient

Phil :

That set of pump speed vs capacity curves are near the bottom of this link,\

Phil :

Look it over and get back to me, we can go from there

Phil :

Phil

Customer:

I am not familiar with the units of the dependent variable on this graph (Total Head (Ft of Water). What is that referring to? How is it calculated or determined?

Phil :

1 pound of pressure per square inch will push up 2.3 feet of water (in a column)

Phil :

that was arranged so that all you had to do, to size a pump pushing water up hill was measure between the bottom of the pump suction to the top of the hill.. to get the pounds pressure per square inch it takes to move the water barely to the top of pipe outlet. then of course you need more pounds pressure to pressurize that outlet so it will push water through what ever device, set of valves and whatever you have a the top of the hill

Phil :

Look that over, see if it makes any sense to you and we can go from there

Phil :

tell me how many times per day you want to turn the water in your pool and I will give you an approximate speed setting for your pump

Phil :

Phil

Customer:

So, then... to be accurate with my calculation, I really need to know the vertical distance between the suction intake at the pool, and the pump. If I can determine that value, that would be the "total head"?

Phil :

Hello again, total head would have to include the pressure losses in ft of head, through the filter, pipe fittings, valves and exit and entry losses from the discharge outlet into the pool at the suction from the pool... a fairly extensive calculation

Phil :

in your case there is generally no need to be that precise.

Phil :

You will probably end up running the pump at 1/2 speed, then if you deem that is not getting the water clean enough .. you will speed the pump up... then later you might find you need to run it faster in the summer than in the winter etc.

Phil :

Let me know if you need further elaboration

Phil :

We can go from there

Phil :

Phil

Customer:

So... I'm really just looking at trial-and-error?

Customer:

Are there no estimates for friction-dependent pressure reduction, per unit distance, in a 3" pipe, that you are aware of? I recognize changes in direction at angled couplings will also increase frictional resistance and attenuate pressure accordingly. This is a programable, variable speed pump, and I'd like to be able to calculate as close as possible, a program that will maximize energy efficiency in accomplishing the necessary filtration.

Phil :

Hello again, Ive been engineering these sorts of systems for 50 years, lately mostly larger ones in buildings and for industry,

Phil :

Doing a that calculation will take data that you and I are probably not privy to, such as the pressure drop at the suction intake protection plate, and how many elbows and if they are long radius or short radius etc

Phil :

also the pressure drop varies through the sand filter is loads up and flushes and then seasonally gets a more thorough cleaning, then there are line strainers. the load with debris.

Phil :

botXXXXX XXXXXne its not worth the effort because the pressure drop changes constantly.. that is why they have provided you with variable speed.. that is designed to solve all these issues.

Phil :

Here at JA, though I am qualified, the fee structure will not support such extensive calculations, and if it did I would advise not to waste your time, due to these very large pressure drop variables, that change daily, through the filters, and strainers...and over time as the pipe surfaces accumulate various mineral and organic deposits.

Phil :

Then, beyond all that, is the pump rating curves themselves.. they are always optimistic., tested no less by UL labs and certified, but done on a finely tuned test pump.. actual performance falls off, for a range or reasons, impeller fit on the shaft can be a thousandths of an inch off. and the length of straight pipe fit to the pump inlet and suction.

Phil :

the practicalities in this case out weigh what can be calculated by a factor of 5 to 1 or so,

Phil :

Let me know if you need further elaboration, Phil

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