new pump questions

Greetings everybody! I followed this forum several years ago, when I successfully installed a SWG which has been wonderful.

My pump has failed after at least 12.5 years of operation (that's as long as I've owned the house). It's a single-speed Pentair Whisperflo with a 3/4 HP motor, SF 1.6 (5.6/11.2A). It still runs, but the thermal overload trips after 3-4 minutes.

I called my pool guy and asked for a replacement bid. He suggested a variable-speed Pentair Inlelliflo with a 3 HP motor, which he would purchase and install for $2,000. Ouch! I can't bring myself to spend that much money. Besides, the pump lists for $880 on Amazon, and even at $100/hour for the labor, I can't see that it would take more than a couple of hours at most. Also, 3 HP seems totally overkill. I understand it's VS but why oversize it so grossly?

I could replace the motor for about $180, but I suspect I would be better off replacing the entire pump, as I am not sure that the impeller bearings aren't partially responsible for the failure. I am leaning towards the Hayward Super Pump, either the 1/2 HP or the 3/4 HP models. My pool is about 30" x 15" irregular, about 10 or 15,000 gallons. In the summer the pump needs to send water up to the solar panels, about 15 ft or so from the pool level. (The pump is about 8 ft below the pool level but that should not matter much).

I have a few questions.

First, strangely, Amazon lists a 1.0 service factor for the 3/4 HP pump, and 1.6 for the 1/2 HP. Maybe it's a mistake. But the pump I have is 3/4 HP and 1.6 SF, so am I undersizing with either of these?

Second, I can't tell what kind of PVC fitting to use to plumb the pump. The PDF manuals don't say that either. It looks like it's a threaded female, but I can't tell if it's standard. Does anybody know what parts to get, so I don't have to make two separate purchases? I would prefer to put some standard unions.

Third, should I go for a two-speed pump instead? I only need to run the pump 4-5 hours/day, so I could go for a lower flow/longer time. But if the flow is too low, then I fear that air might enter continuously through the solar panels drain valve. I know that this setup works fine so I'd rather be conservative.

Thank you for any help!
Luigi

1. Those motors would be undersized. The motor you want is B2980 (230v) or B2981 (115v)

2. Not sure what you are asking here. IF you replace the motor, you shouldn't need to replace any of the plumbing.

3. Yes, go for a two speed. That would be less up front than a VS but won't save as much on energy.

Thank you and sorry if I didn't explain very well. I am thinking of replacing the entire pump, because it's fairly old and I am not sure that replacing the motor only will fix the problem.

Also, I am thinking of replacing the pump with a 1-speed pump (the 1-speed Hayward Super Pump). I am not sure that a 2-speed pump will work properly because I don't know if, at low speed, the flow to the solar panels in the roof will be sufficient to prevent gravity from pulling air down into the system.

My uncertainty is that I am replacing a 3/4 HP pump with a 1.6 SF with another 3/4 HP pump but with a 1.0 SF. In other words, it's possible that the old pump has been running at more than 3/4 HP---hard to tell. As far as I understand, a 3/4 HP motor with 1.6 SF is really a 1.2 HP motor.

Thanks again!

The wet end of a pump can well out last the motor so replacing just the motor should fix your problem based upon the symptoms you described. You can buy a new pump if want to but I was suggesting that you don't have to if you don't want to. 12 years is a long time.

If you are replacing the entire pump and motor, then the HP and SF really don't matter much. Either will work just fine. HP and SF only matter if you are replacing just the motor and using the same wet end.

As for two speed, I have a two speed pump with solar on a two story roof. I run solar on high speed and use low speed when solar is not required or during the winter. That alone saves quite a bit on energy costs so don't dismiss a two speed so quickly.

Most kind of you, thanks. The two-speed suggestion is very good.