Need a new pump

[flcroc]

So....

My 1 HP Hayward Superpump died and I need a replacement. I'm trying to determine if I can reduce the pump HP, maybe even as far as an uprated Pentair 1/2 HP. The relevant numbers:

18'x36' oblong (oval with straight sides), 3 ft shallow end and 8 ft deep end approx 21000 gallons
IC20 SWCG
(2) 1-1/2" suctions - 1 from skimmer, 1 from main drain
(1) 1-1/2" return line back feeding 2 returns
3.14 sq ft sand filter with Hayward multi-port valve - runs 10 or 11 psi when clean

I'm estimating 35 GPM at about 33 ft head for a 10-hr run time. I figure I will go with a single speed pump due to the SWCG that I have had issues with in the past (will post another topic in the proper place).

I'm confident I can drop to at least a 3/4 HP, but I'm wondering if the 1/2 HP can work. If I had to pick I'd rather run a little longer on a smaller pump than shorten the run time on a bigger one. Any recommendations?

 

[PoolGuyNJ]

If there is something wrong with the pump housing, I can see swapping it. If the motor died, swapping the motor, seal set and impeller will be significantly less money. The rest of the pump is the same and there would be no need for any plumbing changes.

A full rated 3/4 HP would be the right motor.

Scott

 

[mas985]

A 1/2 HP full rated Whisperflo is actually more powerful (i.e. produces higher flow rates) than the 1 HP up rated SuperPump. The 1 HP SuperPump is a fairly small and efficient pump so I would try to fix the pump first.

But I estimate, that you are closer to 52 GPM @ 41' of head for your current pump. If you replaced the motor with a 2 speed 1 HP up rated motor, at low speed, the flow rate should be around 26 GPM which should be enough for most SWCGs.

 

[flcroc]

Thanks to both of you.

The pump housing is crackedand the impeller is locked up so I'm playing it safe and replacing the whole pump unit.

Mas: As far as HP, you're loosely suggesting the 3/4 HP motor uprated to 1 HP, correct? Also, I'm interested in how you calculated the loss and flow...

 

[mas985]

Up rated and full rated are terms used in the pump industry to identify low and high service factor pumps. For pumps in the same pump line, a 3/4 HP full rated pump is identical to a 1 HP up rated pump. Also, if you were to replace your current pump motor, it is a 1 HP up rated motor which is equivalent to a 3/4 HP full rated motor but given the wet end is leaking, replacing the entire pump is a better solution.

Some pumps like the Whisperflo line are more powerful than the SuperFlo or SuperPump series with the same label HP. So in fact a 1/2 HP full rated Whisperflo is more powerful than a 1 HP up rated SuperPump/SuperFlo. So in terms of pump size, they line up this way from smallest to largest and the flow rates that they would provide on your plumbing (High/Low Speed).

SuperFlo 3/4 HP Up Rated (GPM:49/25)
SuperPump 1 HP Up Rated (GPM:52/26)
SuperFlo 1 HP Up Rated (GPM:55/28)
WhisperFlo 1/2 HP Full Rated (GPM: 57) - Only comes in single speed
WhisperFlo 1 HP Up Rated (GPM:63/32) - Same as the 3/4 HP full rated

My main point is that you have to be careful when choosing a pump because the label HP does not give an accurate representation of the pump power. The head curve is a much better indicator of how powerful a pump may be. But as you can see, you currently have one of the smallest pumps available. There is only one that is slightly smaller but it's efficiency is about the same as your current pump. In fact, the efficiency of all these pumps are pretty close.

Lastely, I determined your systems operating point using a hydraulic model that I developed and the information that you provided.

The IC20 has a minimum flow rate of 25 GPM so any of the pumps on low speed would probably work with the SWG unless you have a bypass built in but then you could shut that off.

 

[flcroc]

Gotcha. I just wanted to make sure I was on the same page as you.

Now for some more info (and if we need to move this I don't mind)...

I've been having trouble keeping the pool clean/clear after it really warms up, say after Memorial Day. It doesn't matter what I do with regards to pump run time vs. SWCG run time. The only constant is I have to run the IC20 so much that it drives up the pH andI do that dance all summer long. In my opinion the contractor that installed the IC20 screwed me with a borderline selection and shoudl have at least brought it up so I could decide whether to go with the IC20 or IC40. I'm not convinced that running the pump almost continuously didn't produce an overheat that burnt up this pump.

Anyway, I don't want to do a blind swap like-for-like on the pump if this might be part of the problem (and I realize that without having actual gauge readings we are shooting in the dark) - i.e. over flow/pressure, underflow, etc. I've never seen sand blown back into the pool and I've never had trouble with the Polaris 280. I guess I'm trying to reconcile low-speed pumping and the IC20 with guaranteed turnover.

 

[mas985]

A picture of the pad equipment would help to see how the SWG is plumbed. Also, what size are your return eyeballs? Sometimes you can increase the flow rate some if you change eyeball size.

Also, the minimum recommended flow rate is 25 GPM but I am not entirely sure that the unit will shut off below that. Futher down in the manual is says to operate at a minium of 20 GPM so I don't believe there is a hard lower limit. You might give Pentair a call and get clarification. With the pumps you are considering, the flow rate on low speed is close to 25 GPM but plus or minus a few, I don't think will matter much.

 

[swimcmp]

Manufacturers claim the hardest thing on an electric motor is starting and stopping it. I do believe in their therory though, I have had several customers burn out pumps on timers quicker than comparable systems that run 24/7.