Pump sizing recommendation

[dclatt]

My pump motor failed and I'm in the market for a new one but am confused and a bit overwhelmed by the relationship between head/flow rate/HP. So I suppose I'm here looking for advice.
We have an indoor pool that around 25,000 gallons with a Raypak Avia 399,000btu heater, a Hayward S244T filter (I replaced the sand with the cotton ball style media), Hayward SP0714 multiport valve, and a Hayward 1HP Super pump. I attempted to calculate the head and did so to the best of my ability since I'm not sure how the underground portion of the piping is built. We have 2 pressure returns and a single skimmer that the main drain attached to for run-dry protection. The skimmer to the pump room is 1.5" PVC. I stepped everything in the pump room up to 2" with the exception of the multiport valve and the strainer housing (those step down when entering and up when exiting and will be replaced in the future. I also updated all above ground 90s to sweep 90s. The existing outgoing pipe to the pressure side is 2" but I wouldn't be overly surprised if it steps down to 1.5" when it exits, though I can't even examine where it exits because it's literally under the furnace for the room heat. I did my head calculations based on the idea that the pressure side is 2" all the way since I don't know and that's how it has been set up to exit since we moved in. I calculated the estimated head based on 3 different flow rates; they're as follows:
97.43ft @ 60gpm
68.58ft @ 50gpm
46.17ft @ 40gpm
The heater requires a minimum of 40gpm, and I'm aware of the 44gpm soft-limit of 1.5" pipe so there's a very slim margin before I start wasting energy by going about the 44gpm.
I looked at a Hayward chart plotting different sized pumps against head/GPM and failed to come to a conclusion. The 3/4HP motor looked to fall more closer to the bare minimum I need, the 1HP and 1.5HP lines didn't really make sense to me on how to interpret them as they don't match my GPM/head values anywhere.
So I contacted inyo pools to seek advice because I tend to like the quality of their site and articles. They suggested to me that I get a 1.5HP pump motor.
Does this sound reasonable or will I be overpowered and overworking the pump?
Any advice would be helpful! Thanks in advance!

 

[dclatt]

I forgot to mention that I do not plan on going multi-speed or variable speed as we use WiFi timers to run the pool and then turn it on and off remotely if we want to heat it up more for an evening swim (the Avia heater is WiFi controllable). So I'm just looking at Single speed options. Thanks again!

 

[1poolman1]

My pump motor failed and I'm in the market for a new one but am confused and a bit overwhelmed by the relationship between head/flow rate/HP. So I suppose I'm here looking for advice.
We have an indoor pool that around 25,000 gallons with a Raypak Avia 399,000btu heater, a Hayward S244T filter (I replaced the sand with the cotton ball style media), Hayward SP0714 multiport valve, and a Hayward 1HP Super pump. I attempted to calculate the head and did so to the best of my ability since I'm not sure how the underground portion of the piping is built. We have 2 pressure returns and a single skimmer that the main drain attached to for run-dry protection. The skimmer to the pump room is 1.5" PVC. I stepped everything in the pump room up to 2" with the exception of the multiport valve and the strainer housing (those step down when entering and up when exiting and will be replaced in the future. I also updated all above ground 90s to sweep 90s. The existing outgoing pipe to the pressure side is 2" but I wouldn't be overly surprised if it steps down to 1.5" when it exits, though I can't even examine where it exits because it's literally under the furnace for the room heat. I did my head calculations based on the idea that the pressure side is 2" all the way since I don't know and that's how it has been set up to exit since we moved in. I calculated the estimated head based on 3 different flow rates; they're as follows:
97.43ft @ 60gpm
68.58ft @ 50gpm
46.17ft @ 40gpm
The heater requires a minimum of 40gpm, and I'm aware of the 44gpm soft-limit of 1.5" pipe so there's a very slim margin before I start wasting energy by going about the 44gpm.
I looked at a Hayward chart plotting different sized pumps against head/GPM and failed to come to a conclusion. The 3/4HP motor looked to fall more closer to the bare minimum I need, the 1HP and 1.5HP lines didn't really make sense to me on how to interpret them as they don't match my GPM/head values anywhere.
So I contacted inyo pools to seek advice because I tend to like the quality of their site and articles. They suggested to me that I get a 1.5HP pump motor.
Does this sound reasonable or will I be overpowered and overworking the pump?
Any advice would be helpful! Thanks in advance!

Better choices, DOE legal:
Pentair EC-015583
Sta-Rite 348185

 

[dclatt]

Better choices, DOE legal:
Pentair EC-015583
Sta-Rite 348185

Thanks for the response and I'm looking into those motors now!
I'm not worried about DOE compliancy, in my reading of government regulation of the pool industry it's become quite clear that they are clueless (as usual). But I do want an energy efficient motor regardless, so I found this:

Century (A.O. Smith) 1.5 HP Up Rate Energy Efficient Motor, Round Flange 56J Frame, Single Speed - Model UCT1152 - INYOPools.com

Century 1.5 HP Round Flange 56J Up Rate EE Motor - UCT1152

www.inyopools.com

It's also available in 3/4 and 1HP versions. And it would bolt up to my current housing to get me up and running immediately. I'm more concerned about much power I actually need.

 

[1poolman1]

Thanks for the response and I'm looking into those motors now!
I'm not worried about DOE compliancy, in my reading of government regulation of the pool industry it's become quite clear that they are clueless (as usual). But I do want an energy efficient motor regardless, so I found this:

Century (A.O. Smith) 1.5 HP Up Rate Energy Efficient Motor, Round Flange 56J Frame, Single Speed - Model UCT1152 - INYOPools.com

Century 1.5 HP Round Flange 56J Up Rate EE Motor - UCT1152

www.inyopools.com

It's also available in 3/4 and 1HP versions. And it would bolt up to my current housing to get me up and running immediately. I'm more concerned about much power I actually need.

Can't just slap any motor on and call it good. Too small (3/4) and it burns up. Too large (1.5) and it wastes energy for zero return. There's more to sizing a motor.
When California law made people change to variable-speed there was a lot of resentment until the pool stayed cleaner and the savings have amounted to, for some, more than the cost of the pump.

 

[dclatt]

Can't just slap any motor on and call it good. Too small (3/4) and it burns up. Too large (1.5) and it wastes energy for zero return. There's more to sizing a motor.
When California law made people change to variable-speed there was a lot of resentment until the pool stayed cleaner and the savings have amounted to, for some, more than the cost of the pump.

That's why I've asked inyo and why I'm here looking for further advice. I even stated in my original question how I understand the idea of losing energy due to the 44gpm limitations of 1.5", as well as calculated head, made improvement to my plumbing and sated plans to do more in the future, etc. I'm clearly not just slapping a motor on and calling it good.
I have nothing against variable speed, I just don't need it because I run in strict times cycles and my pool is indoors and does not get any outdoor debris so it doesn't need a 24hr variable cycle. Heck, I don't even have to run constant chlorine to keep the levels good.
I'm not entirely sold on the advice of a single company so I'm here looking for further opinions.
The cost of a variable speed motor takes around 2yrs on average to pay for itself if you're only running at 22gpm, and my heater needs 40gpm to operate at all. The 3/4HP version of the motor I linked would use less than 300 watt hours more than a VS but still meet the 40gpm minimum.
The 1HP version of that same motor runs >= the amps the motors you previously linked do, without the DOE stamp of approval.
I do appreciate your advice, I really do, but historically speaking, government mandates raise prices for questionable outcome.
Say for example that I have a single speed pump running 44gpm (max of 1.5" PVC before significant energy loss). It will take around 9.5hrs to turn over a 25k pool like mine. At the 5.5amps.at 240v like the century motor offers, this is around 12,500 watt hours and my heater is primed to run at all times.
With a VS, it would have to get up to a minimum of 40gpm to run the heater. So assuming the heater doesn't need to run the whole time, we will say it runs for half the volume of the pool. So it likely uses 6250k+ watt hours and still needs to process the rest of the pool. Processing the rest at half of that would take around 10.4hrs and result in another 6250k watt hours. These together add up to the same amount as the 1HP pump. And this will vary greatly depending on time of year and climate. I'd pay 4x as much for a VS motor and save basically nothing.

 

[mas985]

That's why I've asked inyo and why I'm here looking for further advice. I even stated in my original question how I understand the idea of losing energy due to the 44gpm limitations of 1.5", as well as calculated head, made improvement to my plumbing and sated plans to do more in the future, etc. I'm clearly not just slapping a motor on and calling it good.

Keep in mind that reducing head loss with a single speed pump actually increases energy use, not decreases. Shifting the operating point to the right on the head curve uses more energy. This is why a VS works better for lower head loss plumbing because you can reduce RPM to compensate.

Also, 1.5" plumbing does not "LIMIT" flow rate to 44 GPM. That is simply a recommendation. There is no fundamental limit to flow rate in pipes. Only recommendations.

The cost of a variable speed motor takes around 2yrs on average to pay for itself if you're only running at 22gpm, and my heater needs 40gpm to operate at all. The 3/4HP version of the motor I linked would use less than 300 watt hours more than a VS but still meet the 40gpm minimum.

The motor you posted draws over 1600 watts but the Intelliflo3 at 40 GPM on typical 1.5" plumbing draws only 450 watts so less than a 1/3rd. More than likely, they would both need to run for the same amount of time so depending on your electrical costs, it may not take too long to pay for itself.

The 1HP version of that same motor runs >= the amps the motors you previously linked do, without the DOE stamp of approval.
I do appreciate your advice, I really do, but historically speaking, government mandates raise prices for questionable outcome.

Just so we are clear, DOE regulations prohibit the manufacture of single and dual speed pumps not the use. So as long as you can find one, you can use it. So far, motors are excluded from DOE but California has their own regulations which limit what kind of motor you can buy. So you can still find replacement motors if you live outside of CA.

Say for example that I have a single speed pump running 44gpm (max of 1.5" PVC before significant energy loss). It will take around 9.5hrs to turn over a 25k pool like mine. At the 5.5amps.at 240v like the century motor offers, this is around 12,500 watt hours and my heater is primed to run at all times.

Turnovers are irrelevant. They are a very poor predictor of pool cleanliness. Some pools need less that 1/10th of a turnover to keep clean but most don't need even 1 turnover per day. This is why many with VS pumps run 24hr at lower speeds but still do not turnover the pool once per day. It doesn't matter, the pools are clean and perfectly maintained.

Turnover of Pool Water - Further Reading

www.troublefreepool.com

 

[dclatt]

Keep in mind that reducing head loss with a single speed pump actually increases energy use, not decreases. Shifting the operating point to the right on the head curve uses more energy. This is why a VS works better for lower head loss plumbing because you can reduce RPM to compensate.

Also, 1.5" plumbing does not "LIMIT" flow rate to 44 GPM. That is simply a recommendation. There is no fundamental limit to flow rate in pipes. Only recommendations.


The motor you posted draws over 1600 watts but the Intelliflo3 at 40 GPM on typical 1.5" plumbing draws only 450 watts so less than a 1/3rd. More than likely, they would both need to run for the same amount of time so depending on your electrical costs, it may not take too long to pay for itself.


Just so we are clear, DOE regulations prohibit the manufacture of single and dual speed pumps not the use. So as long as you can find one, you can use it. So far, motors are excluded from DOE but California has their own regulations which limit what kind of motor you can buy. So you can still find replacement motors if you live outside of CA.


Turnovers are irrelevant. They are a very poor predictor of pool cleanliness. Some pools need less that 1/10th of a turnover to keep clean but most don't need even 1 turnover per day. This is why many with VS pumps run 24hr at lower speeds but still do not turnover the pool once per day. It doesn't matter, the pools are clean and perfectly maintained.

Turnover of Pool Water - Further Reading

www.troublefreepool.com

I'm aware that 1.5" does not limit flow, that's why I referred to it as the max before significant energy loss. The pump works harder when you push beyond the "limits" and you become leff efficient.
I was using turnover as a measure of time and a simple way to compare energy costs. I could have used any set period of time but it was just what I picked at the time. I don't do full turnovers on mine because it stays far more clean being indoors.
I understand that DOE doesn't limit buying them, that would be impossible.
And I'm not sure whether it would need to run at the same amount of time, that seems dependent on GPM. Plus running slower through the heater causes energy loss there. So running at the bare minimum of my heater wouldn't be efficient at all. This is part of my dilemma as well. Greater heat loss through pipes at slower speeds and it would spend more energy attempting to heat water longer at a higher heat point as it moves slower vs cycling in more water at faster at a slightly lower temperature.
What I am curious about is how reducing head loss with a single speed pump would increase energy loss? I was under the understanding that if I run at a lower speed then my head decreases and so does energy usage due to needing a lesser HP motor. But I my issue is that I'm not even sure if the lesser HP motor will work due to the amount of head I have and it reducing my GPM below my minimum operating flow.
I'm not trying to move the curve to the right, as you say. I assume you're referring to buying a bigger pump motor to achieve more GPM. I know that this increases head. My problem is that I have so much head that I'm not sure the lower HP motors are pushing enough to meet my minimum GPM. I literally had an 18 month old 1HP century motor burn up that never ran dry. This is after installing the new heater with new plumbing, etc which added a significant amount of head to the system and I worry that I'm underpowered and causing the motor to burn up. Or it could have just been a bad motor. Hard to say. I understand that head loss and GPM are directly related in the sense that more GPM increases head and less decreases. That's why I've done all of the calculations for head loss at different GPM. And with the amount of head that I have, I would need at least a 3/4HP motor to push a minimum of 40GPM. I think that may be the info that your 40GPM at 450watts is missing.
I'm also curious as to where you get your information for the intelliflo only using 450watts at 40gpm, this making it roughly a 2A draw at a listed 230V. I've downloaded pamphlets, brochures, manuals, etc and have never found any info on that. I would assume that's running at 1/4 - 1/2HP?

 

[mas985]

And I'm not sure whether it would need to run at the same amount of time, that seems dependent on GPM.

There are several factors that determine run time dependent on your setup. Run time is mostly determined by the chlorination method (SWGs require more time than manual dosing), heating requirements (solar requires time when the sun shines or a HP requires a certain amount of time to heat) plus skimming (this has some GPM dependencies but usually it is usually much shorter than the other requirements). Skimming only dominates without SWGs and without heating requirements but even then, flow rate has less impact than you would think. Running have half speed does not necessarily mean that you need to run twice as long. Sometimes flow rates can be too fast and debris can rush past the skimmer.

Plus running slower through the heater causes energy loss there. So running at the bare minimum of my heater wouldn't be efficient at all.

Actually, it is not as bad as you think. It is true that slower water has higher heat loss but the pipes have a fixed surface area and PVC is not all that good and thermal transfer (<1% relative to metal) plus dry earth is a pretty good thermal insulator so the amount of heat loss does not change that much by GPM until you get to very low GPM levels. The pool loses far more heat than the pipes so the pipes are comparitively insignificant. It may become significant for pools with insulated covers and walls but it is still small.

What I am curious about is how reducing head loss with a single speed pump would increase energy loss? I was under the understanding that if I run at a lower speed then my head decreases and so does energy usage due to needing a lesser HP motor.

Yes, this part is true. Lower RPM results in lower head loss but ALSO lower GPM. The energy used to turn the impeller is proportional to the product of head loss AND GPM. With a centrifugal pump, GPM increases faster than head loss decreases when moving left to right on the head curve so the product increases and thus the power required increases.

But I my issue is that I'm not even sure if the lesser HP motor will work due to the amount of head I have and it reducing my GPM below my minimum operating flow.

With lower HP pumps, the GPM drops but the head loss does as well. The pump affinity equations show this relationship as well as the hydraulic HP relationship:

• GPM B = GPM A * (RPM B / RPM A)
• Head B = Head A * (RPM B / RPM A) ^ 2
• Hydraulic HP B = Hydraulic HP A * (RPM B / RPM A) ^ 3

There is more information in the Hydraulics 101 sticky:

Hydraulics 101 - Have you lost your head?

Edit - Before reading this article, you may want to first familiarize yourself with this Pool School article on Pump Basics Hydraulics 101 - Pump Head Curves, Plumbing Head Curves and Operating Points Hydraulic Head In fluid dynamics, head is a concept that relates the energy in an...

www.troublefreepool.com

But note, these formulas only apply to the same plumbing curve (i.e. fixed plumbing). When you change the plumbing the plumbing curve shifts along the head curve. So this is not the same effect.

I'm also curious as to where you get your information for the intelliflo only using 450watts at 40gpm, this making it roughly a 2A draw at a listed 230V. I've downloaded pamphlets, brochures, manuals, etc and have never found any info on that. I would assume that's running at 1/2HP?

You won't find that information in any manufacture's brochure with the exception of the original Intelliflo which has a published head and energy curves:

Note how power increases from left to right. This happens will all centrifugal pumps.

However, a number of years ago before the DOE regulations, there were several sources of residential pool pump power databases where you could obtain information about various pumps. I put together a spreadsheet of all the various sources and data here:

Pump Database

docs.google.com

Each pump was measured on three different plumbing curves. These are defined as follows:

Curve A Head (ft) = 0.0167 * GPM^2 - Typical 1.5" Plumbing
Curve B Head (ft) = 0.05 * GPM^2 - Really high head loss Plumbing
Curve C Head (ft) = 0.0082 * GPM^2 - Typical 2" Plumbing

Using this data and theoretical formulations, I am able to interpolate and extrapolate to get any energy use for any plumbing system, any pump (in the DB) and any RPM. There are spreadsheets in my signature that do this automatically. There is also a spreadsheet that will compare the lifetime cost of various pumps for different plumbing systems so you can see more precisely how long will take for payback. Also, these spreadsheets can help predict flow rates for various pumps and plumbing configurations.

Hydraulics 101 - Have you lost your head?

Edit - Before reading this article, you may want to first familiarize yourself with this Pool School article on Pump Basics Hydraulics 101 - Pump Head Curves, Plumbing Head Curves and Operating Points Hydraulic Head In fluid dynamics, head is a concept that relates the energy in an...

www.troublefreepool.com

 

[dclatt]

There are several factors that determine run time dependent on your setup. Run time is mostly determined by the chlorination method (SWGs require more time than manual dosing), heating requirements (solar requires time when the sun shines or a HP requires a certain amount of time to heat) plus skimming (this has some GPM dependencies but usually it is usually much shorter than the other requirements). Skimming only dominates without SWGs and without heating requirements but even then, flow rate has less impact than you would think. Running have half speed does not necessarily mean that you need to run twice as long. Sometimes flow rates can be too fast and debris can rush past the skimmer.


Actually, it is not as bad as you think. It is true that slower water has higher heat loss but the pipes have a fixed surface area and PVC is not all that good and thermal transfer (<1% relative to metal) plus dry earth is a pretty good thermal insulator so the amount of heat loss does not change that much by GPM until you get to very low GPM levels. The pool loses far more heat than the pipes so the pipes are comparitively insignificant. It may become significant for pools with insulated covers and walls but it is still small.


Yes, this part is true. Lower RPM results in lower head loss but ALSO lower GPM. The energy used to turn the impeller is proportional to the product of head loss AND GPM. With a centrifugal pump, GPM increases faster than head loss decreases when moving left to right on the head curve so the product increases and thus the power required increases.


With lower HP pumps, the GPM drops but the head loss does as well. The pump affinity equations show this relationship as well as the hydraulic HP relationship:

There is more information in the Hydraulics 101 sticky:

Hydraulics 101 - Have you lost your head?

Edit - Before reading this article, you may want to first familiarize yourself with this Pool School article on Pump Basics Hydraulics 101 - Pump Head Curves, Plumbing Head Curves and Operating Points Hydraulic Head In fluid dynamics, head is a concept that relates the energy in an...

www.troublefreepool.com

But note, these formulas only apply to the same plumbing curve (i.e. fixed plumbing). When you change the plumbing the plumbing curve shifts along the head curve. So this is not the same effect.


You won't find that information in any manufacture's brochure with the exception of the original Intelliflo which has a published head and energy curves:

Note how power increases from left to right. This happens will all centrifugal pumps.

However, a number of years ago before the DOE regulations, there were several sources of residential pool pump power databases where you could obtain information about various pumps. I put together a spreadsheet of all the various sources and data here:

Pump Database

docs.google.com

Each pump was measured on three different plumbing curves. These are defined as follows:

Curve A Head (ft) = 0.0167 * GPM^2 - Typical 1.5" Plumbing
Curve B Head (ft) = 0.05 * GPM^2 - Really high head loss Plumbing
Curve C Head (ft) = 0.0082 * GPM^2 - Typical 2" Plumbing

Using this data and theoretical formulations, I am able to interpolate and extrapolate to get any energy use for any plumbing system, any pump (in the DB) and any RPM. There are spreadsheets in my signature that do this automatically. There is also a spreadsheet that will compare the lifetime cost of various pumps for different plumbing systems so you can see more precisely how long will take for payback. Also, these spreadsheets can help predict flow rates for various pumps and plumbing configurations.

Hydraulics 101 - Have you lost your head?

Edit - Before reading this article, you may want to first familiarize yourself with this Pool School article on Pump Basics Hydraulics 101 - Pump Head Curves, Plumbing Head Curves and Operating Points Hydraulic Head In fluid dynamics, head is a concept that relates the energy in an...

www.troublefreepool.com

My original post accounted for the information about the correlation between head loss and GPM. I appreciate all of the advice but the further this conversation goes on the more confused I am of whether you actually read my original post in its entirety. But that's the point. I've done head loss calculations at multiple different GPMs, as listed in my original post. You're saying I could move 40GPM at 450watts but according to the graph you shared, that would be with a head of ~20ft. I don't have that. I have 40-50ft.

 

[1poolman1]

My original post accounted for the information about the correlation between head loss and GPM. I appreciate all of the advice but the further this conversation goes on the more confused I am of whether you actually read my original post in its entirety. But that's the point. I've done head loss calculations at multiple different GPMs, as listed in my original post. You're saying I could move 40GPM at 450watts but according to the graph you shared, that would be with a head of ~20ft. I don't have that. I have 40-50ft.

Head number go "out the window" when the water slows down. As a rough measurement, for any given speed you can take a pressure reading at the filter in PSI and a suction reading at the pump in inches of mercury. Multiply the pressure by 2.31 and the suction by 1.13. Add them together and that is the total head on the system at that moment with the filter as dirty as it is, conditions are constantly changing in a pool. Slow the pump down and both numbers drop while the actual plumbing remains static.

 

[mas985]

Head loss changes with flow rate. How did you calculate it? Again, the spreadsheets might be helpful.

 

[mas985]

97.43ft @ 60gpm
68.58ft @ 50gpm
46.17ft @ 40gpm

Ok, so these numbers tell me that the plumbing curve is 0.027 which is very poor and much worse than typical 1.5" plumbing. This is the reason I didn't put too much credence into these numbers. They don't look correct.

But if they are correct, then the Intelliflo3 would use about 760 watts @ 2500 RPM (same flow rate and head as you posted).

 

[dclatt]

Ok, so these numbers tell me that the plumbing curve is 0.027 which is very poor and much worse than typical 1.5" plumbing. This is the reason I didn't put too much credence into these numbers. They don't look correct.

But if they are correct, then the Intelliflo3 would use about 760 watts @ 2500 RPM (same flow rate and head as you posted).

That's not just plumbing, that takes into consideration loss of everything else:

Head loss at multiport valve
16.17ft @ 60gpm
11.55ft @ 50gpm
6.93ft @ 40gpm

Head loss from heater
19.5ft @ 60gpm
16.5ft @ 50gpm
13.4ft @ 40gpm

Head loss from filter (sand, as I could not find data on how the filter balls effect the head loss)
31ft @ 60gpm
21ft @ 50gpm
14ft @ 40gpm

As well as head loss from pipe and pipe fittings.

Maybe my findings are wrong. I've went over and revised it countless times. Counted all the couplings, curves, tees, unions, feet of 2", feet of 1.5", elevation between water and pump, etc. I could give you all of that data if you want. I honestly may not be doing it right. I'm just going off of articles that I've read on sites like inyo. I mean, just the 3 items I listed about already have a head loss of 34.33ft @ 40gpm prior to adding in the pipe and fittings.
Don't get me wrong, I really do appreciate your advice and you clearly know faaaarrrr more than I do. I just think we're possibly having a failure in communication at times.
I'll have to look into your calculators in your signature.
Something I am taking away from this is that I could possibly buy a variable speed pump and run it at a lower RPM to save power. I really don't know that I would get the full benefit of a $1k intelliflo, but I was interested in this one:

Century (A.O. Smith) 1.65 HP Motor, V-Green, Round Flange 56J, Variable Speed, 208-230V - Model ECM16CU - INYOPools.com

V-Green 1.65 HP Round Flange 56J Variable Speed Motor - ECM16CU

www.inyopools.com

Any thoughts?

 

[mas985]

That would be a better choice than a SS motor.

What is the make/model # of your current pump?

You may want to change the impeller as well.

Other things that cause head loss are skimmers, MDs, eyeballs. Basically anything that touches the water adds head loss. Everything needs to be included if you want to do it right. Also, splits in the plumbing complicates things. It isn't a trivial calculation. Some web sites make you think it is simple and sometimes have calculators but they almost always miss something. Also, when I use the term plumbing, it means anything that touches the water, equipment included.

 

[dclatt]

That would be a better choice than a SS motor.

What is the make/model # of your current pump?

You may want to change the impeller as well.

Other things that cause head loss are skimmers, MDs, eyeballs. Basically anything that touches the water adds head loss. Everything needs to be included if you want to do it right. Also, splits in the plumbing complicates things. It isn't a trivial calculation. Some web sites make you think it is simple and sometimes have calculators but they almost always miss something. Also, when I use the term plumbing, it means anything that touches the water, equipment included.

Yeah I added everything except the eyeballs, main drain, and skimmer because I couldn't find values for it. All of the math I found for fittings was done at 70GPM values so I multiplied it by .66 for 60GPM, then again for 50 and again for 40; because I noticed that the trend with most head loss/gom correlation is around 1/3 less head for every 10GPM less.
I couldn't find values for the main drain, eyes, and skimmer.
How does that motor I just linked compare to the intelliflo in your opinion? Aside from the obvious higher HP listing.

 

[mas985]

Yeah I added everything except the eyeballs, main drain, and skimmer because I couldn't find values for it. All of the math I found for fittings was done at 70GPM values so I multiplied it by .66 for 60GPM, then again for 50 and again for 40; because I noticed that the trend with most head loss/gom correlation is around 1/3 less head for every 10GPM less.

That isn't quite correct. Head loss varies with gpm^2 as the affinity equations show. In fact, you just need one gpm/head value to calculate the plumbing curve and that is good for all GPM and head values.

Head (ft) = C * GPM^2

C = Head (ft)/GPM^2

Then you can add all the C values for each piece of serial plumbing to get the total plumbing curve. But again, parallel plumbing reduces head loss because flow is split so you have to take that into account as well.

How does that motor I just linked compare to the intelliflo in your opinion? Aside from the obvious higher HP listing.

The higher HP means for a given flow rate, the RPM can be lower which means lower noise and usually better efficiency.

Also, it will talk to other Pentair equipment which is a plus IF you have a Pentair controller.

But you need to match the motor with the impeller which is why I asked the current pump make/model#.

 

[dclatt]

That isn't quite correct. Head loss varies with gpm^2 as the affinity equations show. In fact, you just need one gpm/head value to calculate the plumbing curve and that is good for all GPM and head values.

Head (ft) = C * GPM^2

C = Head (ft)/GPM^2

Then you can add all the C values for each piece of serial plumbing to get the total plumbing curve. But again, parallel plumbing reduces head loss because flow is split so you have to take that into account as well.



The higher HP means for a given flow rate, the RPM can be lower which means lower noise and usually better efficiency.

Also, it will talk to other Pentair equipment which is a plus IF you have a Pentair controller.

But you need to match the motor with the impeller which is why I asked the current pump make/model#.

Yeah I figured that the values for different flow rates for fittings likely wasn't entirely correct but I was trying to get a rough estimate. The fittings don't make a massive impact overall, I just wanted it to be as close as possible. I used the data on the inyo article to come up with my numbers and then owners manuals for my heater, filter, etc. The fittings were the only part that didn't have values given for different flow rates already.
And yeah I knew I would need a whole new impeller and such. I've been hesitant to do a VS motor due to the cost and the fact that I'll most likely just use it as a single speed motor due to how we run our pool. But one thing I was missing was the relationship between RPMs and watts.

 

[reggiehammond]

I love the discussion, but the Calimar 3HP VSP is $519.

 

[dclatt]

I love the discussion, but the Calimar 3HP VSP is $519.

I've seen ones with great ratings on Amazon that were 3HP VS for good prices as well. I'll definitely take your suggestion into consideration! I'm hoping to place an order this weekend but choosing the correct motor/pump has proven far more difficult than I ever anticipated.