Replacement pump selection for 50,000 gal inground pool

[Mmonaco]

First off, thank you all for your help! I've been using this board for the last year and the information on it has been very helpful.

I purchased an in ground vinyl liner pool (used off craigslist, but that's another story) and installed it August of last year.

The equipment came with the package - a Pentair Challenger 1.65 THP pump and 2 Pentair Tagelus 50GPM Filters.

I want to replace the pump for 2 reasons:

1. Electricity is expensive! $.40 per KWH. California does one thing better than any other state - high energy costs.
2. I need a pump for something else that doesn't get used often.

I love the idea of a variable speed pump, and know in the long run it may save more money, but that's if there isn't a problem with the electronics after the warranty runs out. I don't like the idea of not being able to 'just' replace the motor if there is a problem. Plus there is only a 1 year warranty which seems crazy for such an expensive pump.

So i was thinking of a 2 speed pump.

Currently i have a 1.67 THP pump running at 8Amps that pushes 90GPM at 40' of head. It did a great job all last year keeping my pool clean, and i ran it far less than is recommended (no full turnover per day.)

So, with energy efficiency in mind, I was thinking about the WhisperFlo 2 speed pump series. It will pump 100GPM at 40' of head at 7.8A. That's more water and less electricity. Plus there's a low speed, which i will use often.

The Superflo series doesn't seem to give me a benefit. It uses less electricity than what i am replacing, but only has 80 GPM at 40' of head.

BUT - I now realize my filters are rated for 100GPM combined. From all I've read, filters are better if oversized, and I'm pushing it here.

Although i haven't calculated my head, my guess is it's pretty low. I have 2 skimmers with 2" pipe, and a main drain with 1 1/2" pipe. I use 3-4 returns with 1 1/2" pipe. The filters run at 10PSI.

So here are my questions:
Am I crazy to not want a VS pump?
Should i upgrade my filter (or buy a third?) How oversized should it be?
And most importantly - Are there recommendations on an energy efficient 2 speed pump besides the Whisperflo pump series? Should i be looking at Hayward or another manufacturer?

Hopefully this makes sense. Thank You in advance for your help! This is a great forum and i hope to be able to contribute here and give back once i figure out what I'm doing!

Matt

 

[JasonLion]

You aren't crazy to not want a variable speed, even though that is what I would recommend given your electrical rates. Problems with variable speeds are fairly rare, but they do happen. In effect you are gambling the the pump won't have any problems. Going with a two speed will have a higher expected total cost, but is less money up front and lower risk of expensive problem later. You get the majority of your savings by going to a two speed, so even though a variable speed would save more, it isn't a huge amount more.

You might want to consider the 3/4 HP WhisperFlo. That would be a bit smaller than your 1.5 HP Challenger, but safer for your filter. The superFlo is only interesting when you want something even smaller than the 3/4 HP WhisperFlo, since the SuperFlo is actually a smaller pump than the WhisperFlo at the same HP rating. mas985 will have a better grasp of which pump is most appropriate. Hopefully he will stop by soon.

 

[Mmonaco]

Thanks for the information! I was thinking about the 3/4 HP Whisperflo, but I keep dismissing the idea because the pool is so big. That being said, the pump would be plenty big enough, but I may have to run it longer if I run into water quality issues.

I'll stop looking at the Superflo.

Matt

 

[mas985]

The 3/4 HP Whisperflo is probably a good choice but just to make sure, it might be worth while to run some calculations on the plumbing.

Although i haven't calculated my head, my guess is it's pretty low. I have 2 skimmers with 2" pipe, and a main drain with 1 1/2" pipe. I use 3-4 returns with 1 1/2" pipe. The filters run at 10PSI.

So does this mean the suction pipes run all the way to the pump individually and combine at the pump?

What is the length of each suction line?

What is the filter gauge height relative to the pool water level?

 

[woohoo]

Being in California, have you checked into rebates on the variable speed pumps? Might be worth it to look into it and see what the rules are regarding
purchase on-line vs. local, etc. Are you using automation at all? If so, the manufacturer of the automation might be the same way to go if you opt for
a variable speed pump. Good luck.

 

[Mmonaco]

There is a $100 rebate on a VS pump from our electric provider, and it looks like it can be purchased anywhere. I am not using automation and don't plan to in the near future.

The suction lines are approximately:
2" - 30' long
2" - 70' long
1.5" - 30' long

There are 2 skimmers on either side of the pool. The pad is closest to the deep end skimmer and main drain.

The lines combine at the pad right before the pump. All suction and returns were run separately.

The filter gauge is 3' above the water level.

I've seen these calculations made here, but where do you go to get information on making them? Everything i have seen is not directly related to pools.

Thanks for all the help everyone!

Matt

 

[mas985]

Hydraulic theory is universal and it really doesn't matter if it is a pool, house or water distribution system, the theory is the same. I developed my own tools to do the calculations but they are based upon several sources of data. The main source of pump data comes from the California Energy Commission's appliance database which shows the energy consumption of various pumps on three different sets of plumbing systems. The plumbing model is a variant of the Darcy-Weisbach empirical model. The fitting loses are based upon the Crane TP-410 manual. Finally, it is important to understand the theory so you can put all the pieces together. Because there is some information that is unknown, there is also a little bit of guess work involved. If you want to learn more about hydraulics, I recommend pumped101.com and I also have a few more links in the Hydraulics 101 sticky.

Anyway on to your pool. I have a few more questions.

Does the filter gauge go to zero when the pump shuts off?

Are there 3 or 4 return lines and what size are the eyeball openings?

Is your pad plumbing 1.5" also?

The Challenger pump that you have is it the high head or high flow version? Do you have a model#?

Is the pump really loud?

The reason I am asking more questions is because the operating point I am estimating is beyond runout for the pump.

 

[Locksmythe]

Does a loud pump mean something in particular to you here?

 

[Mmonaco]

Sorry for the delay - I was out today.

I primarily use 3 1 1/2" return lines, all have eyeballs on them, but i could use up to 4, and take eyeballs out of some.

The filter gauge does go to 0 when the pump shuts off.

The pad plumbing is all 2".

The Challenger pump is a CFII-N1-1-1/2A. It looks like it's a high flow pump.

The pump does not seem abnormally loud. If i restrict the number of returns or the suction lines, it does get louder, but as long as 2 returns and at least one of the skimmers is wide open it sounds 'normal.' I don't have any flow gauges, but it moves lot of water!

Thanks for all the help. I'll check out the sticky and the website later tonight.

Matt

 

[mas985]

Everything makes sense now. The difference was the high flow instead of the high head pump. Your plumbing is well suited for a medium head, high flow pump. Anyway, here are the operating points:

Challenger High Flow Operating Point

95 GPM @ 35' head & ?? watts, 9 hour turnover


Whisperflo WFDS-24/3 Estimated Operating Point

High: 94 GPM @ 34' head & 1600 watts, 9 hour turnover
Low: 47 GPM @ 9' head & 373 watts, 18 turnover

As you can see the Whisperflo can deliver about the same flow rate as the Challenger on high speed. The label HP of a pump can be a very poor indicator of a pump's true power. But if you compare the head curves of the two pumps, they are fairly close. I can't estimate the wattage of the Challenger because I don't have any test data for that pump but since the operating point is pretty close to the Whisperflo, my guess is the wattage should close as well.

Given that the performance of the two pumps is nearly the same, one alternative that would be easier and cheaper to do would be to just replace your current motor with a two speed.

 

[Mmonaco]

Well, I asked, and everyone said to get the smaller 2 speed Whisperflo, so that's what I'm doing!

I'm going to keep the challenger pump and use it for another project - it won't go to waste.

As an aside - I measured the energy usage of the pump with a my TED (The Energy Detective) and it consumed almost exactly 2000 watts. The nameplate says 8A at 230V, or 1840 watts. hmm..

Anyway, that being said, if i run the pump for 1 complete turnover a day on high speed, I save $.64 a day, or $230 a year.
If i run a complete turnover a day on low speed, i save $3.71 a day, or $1350 a year. Wow!

As a disclaimer - I'm comparing what looks like professional testing data with data from a relatively inexpensive home energy monitor. It's probably not accurate, but even if it's off by 20%, it's still worth the expense of a 2 speed pump. It will be interesting to see what TED says when i run the Whisperflo.

Again, thank you for the help everyone! It was much appreciated.

Matt