Intelliflow requires high RPM to function...why?

[beachbons]

I have a 15,000 gal inground with a Whisperflow pump with 1/2 hp motor & sand filter with Master Temp 400 propane heater. We are located 250 ft from the Gulf of Mexico. The motor was going into its 5th year of service when it seized. Up to that point the motor always performed well with no problems. We have 1 1/2 inch water lines.

My pool person installed an Intelliflow motor and control to the existing Whisperflow pump.

First problem was that the pump would not prime at the prime RPM of 3250. It sucked the water out of the lines too fast, according to the installer. He said that the lines should be 2" and not 1 1/2". He then reduced the Prime speed to 2400 RPM. This allowed the pump to prime each morning. OK, we seem to have the problem solved, except, the pump will not fill the "bowl" and maintain flow unless the constant speed is 2350 RPM. Additionally, the heater will not remain "on" unless the 2350 RPM is maintained to keep the water flowing.

Pentair Factory Rep has agreed that the 2350 RPM is probably necessary to maintain flow. My question is, do I really need an Intelliflow if I must always run it at 2350 RPM's....I'm sure my savings is greatly diminished. Should I go back to a single-speed?

I have the Intelliflow on two other inround pools with no problems. They run at 3250 rpm for prime and 900 rpm for normal operation.

 

[Bama Rambler]

Welcome to TFP.


So the pool person stuck an Intelliflo motor and drive on a ½hp impeller? If that's the case, I don't doubt that it needs to run that impeller pretty fast to get it to prime and run with enough flow. You could have them change out the impeller to a larger size or you could have them install a 2-speed motor.

Now for a couple of questions.
1. Did they happen to change the impeller?
2. Is there any air in the pump basket when it's running at 2350 rpm?
3. What is the filter pressure when the running at 2350?
4. How far is it from the pool to the equipment pad?
5. Can you post a pic of the equipment pad?

(Yeah, I know that's more than a couple)

 

[Divin Dave]

Hi, and welcome to TFP.
is your old motor really a 1/2 HP, or is that a typo and you really meant 1 1/2?

 

[JasonLion]

Welcome to TFP!

If they only replaced the motor, and reused the existing impeller then the RPM limitations sound very reasonable. There isn't much point to running an IntelliFlo with a 1/2 HP impeller. Still, you will save some electricity over your old setup. The IntelliFlo motor has a higher inherent efficiency and you are running it at less than full speed, both of which will save on electricity.

 

[beachbons]

Thanks for the replies. So, the impeller should be rated to the motor? The installer used the same impeller. I spoke with a factory rep from Pentair and he never mentioned this as a possible concern. He spoke highly of the installer.

There is air in the basket at 2350 RPM; even more air at lower RPM. My other two pools with intelliflows have full baskets of water at 900 RPM
Filter pressure is 20 after back-wash.
The equipment is located about 15 ft from the pool and is on a 3 foot elevated platform due to building codes.

 

[JasonLion]

It is fine to run the pump with a smaller impeller, as long as you don't mind the lower flow rate. The behavior will be very different from what you would see with the standard IntelliFlo impeller. That is not necessarily a bad thing.

Seeing some air in the strainer basket at low speeds is normal. Since the impeller is smaller than expected, the effective speed is much lower than the actual speed, so what you describe is exactly what I would expect for that setup. It will not behave like other IntelliFlo pumps, because it has a different impeller. You will need to run it on a much higher speed than you would if it had the stock impeller to get the same effect. As long as you don't need to move all that much water around that isn't a problem.

 

[Bama Rambler]

I'll just jump in and agree with Jason that what you're seeing with a ½hp impeller is expected and that you can't compare it with any stock Intelliflo.