Using calculated head from old pump to size new pump?

[MitchRyan912]

According to the photos I took from my old pump, I was getting readings of 2" vacuum and about 20-25 psi of pressure, so that means I'm getting total head of about 48-60 feet of head with a 1.25 SFHP pump on high speed (3/4 HP x 1.6 SF). Unfortunately, I went through 3 motors last year (all burnt out) and am ready to scrap the wet end and buy a whole new pump, preferably 2-speed.

Are these number meaningful in any way to determine what I should be getting next, or is it only meaningful if I'm looking at a similarly rated 1.25 SFHP pump?

I'm wondering if I should get something slightly larger, like a 1.5 SFHP pump, but run it on its lower speed most of the time?

 

[jblizzle]

Why do you think you need to go larger? If you kept burning out motors, seems like a mismatch of the impeller and motor.

Do you have any high flow needs, if not, get a 1 hp 2 speed.

 

[MitchRyan912]

First motor came with the wet end, a single speed 1 HP with a SF of 1.25. It ran fine one season, then was burnt up at the midway point of its second season. I still have no idea why this happened.

Second motor was replacement but on the same wet end as above. It was a two speed 3/4 & 1/6 HP w/ SF of 1.6. First one burnt up nearly immediately, and a warranty replacement (third motor) burnt up within 6 weeks. I did not change the impeller when I put this two speed motor on the wet end.

At this point, it seems as is the motors I had were either too big or too small. I could never get the pump fully clear of air, as the basket would only get to about 90-95% full of water. When it would malfunction, it would almost get to fully primed, then the high speed would go into a thermal protection mode of sorts, but not fully shut down. I could switch it to low speed and it would run fine for about a minute, then it would shut down completely. It just seemed as if it was struggling to have enough power to pull water through the suction lines.

 

[jblizzle]

There had to be something wrong in the pump or a mismatch.

A pool pump should work fine regardless of the size on nearly any plumbing. Bigger pumps cost more, move more water, and use more power. Smaller pumps cost less, move less water, and use less power.

The wet end determines the amount of water moved. The same HP motor will move more or less water depending on the wet end design.

 

[MitchRyan912]

Had a builder come out to give a quote, and he suggested that the old house electrical panel may have played a part in the problem with these pumps failing, in that the panel was allowing too much current and not popping the breakers as it probably should have (I've taken readings as high as 45 A!)

Too much current = too much heat = possible deformed impeller and/or wet end. He also pointed out something I had done with the plumbing on the suction side (after the 1st motor failure) that likely overworked the 2nd and 3rd motors, which eventually caused too much current to be drawn.

That said, the builder says I should put a 1 HP Max E Pro (unclear if he means 1 HP or 1 SFHP) if not a bigger one, and recommended replacing my filter as well, "because it's 20 years old." I don't have any strong feelings about the filter, as I rebuild its guts last year (new laterals and hub), but I don't know if I did it properly. I'm pretty sure that the 1.25 SFHP single speed pump (P6E6D-205L) or the 1.65 SFHP dual speed pump (P6RA6YF-206L) are what I will end up wanting, but I think he's gonna push for larger...