Matching impeller to motor

[colesdaddy]

Current Specs:

Pump model: Sta-Rite Max E Pro
Motor: AO Smith (Century) SQ1152 1.5HP 1.47SF = 2.2 total HP <--- I believe this is a replacement motor from the previous owner
Impeller: C105-238PDBA (1.5 hp FR/2.0 hp UR)

I've got it pulled apart to tune up the pump since it was leaking. The seal and o-ring kit is on the way. However, the impeller is rated at 1.5 hp full rate and 2 hp uprate. I don't think they changed it when the motor was changed. I'm looking at the specs for the next impeller up, C105-238PEBA, and it's rated for 2 hp full rate/2.5 uprate. My brain is telling me to change the impeller to the higher rated model. What say you?

 

[ajw22]

It is doubtful you need a 2+ HP impeller. However we cant comment without knowing the equipment the pump is supporting.

Please read this before you post and put the details of your pool in your signature.

 

[colesdaddy]

It's an inground pool about 20x45' ~30,000 gallons ish. Has a Sta-Rite SRM-150 filter. Has a separate 3/4 HP booster pump for the sweep. Anything else?

 

[JamesW]

You can't upsize the impeller without a bigger motor.

The bigger impeller will burn out the motor.

If anything, I would go to a smaller impeller.

Is there any reason you need high flow?

 

[colesdaddy]

I was just looking at the impellers and comparing the specs relative to the motor and it seems reasonable that if the motor/pump and the rest of the equipment can handle the increased flow rate, then why not? You're saying the motor will be too stressed with the larger impeller, even though the impeller specs say otherwise?

Also, why go even smaller than what I have now? What dis/advantages does that give me over my present situation? Thanks.

 

[mas985]

I've got it pulled apart to tune up the pump since it was leaking. The seal and o-ring kit is on the way. However, the impeller is rated at 1.5 hp full rate and 2 hp uprate. I don't think they changed it when the motor was changed. I'm looking at the specs for the next impeller up, C105-238PEBA, and it's rated for 2 hp full rate/2.5 uprate. My brain is telling me to change the impeller to the higher rated model. What say you?

That impeller needs at least a 2.5 THP motor. So your motor is too small.

But in general, the smaller the impeller, the lower the energy use so the simple answer as to why go with a smaller impeller, is to save money.

 

[colesdaddy]

I see. Thanks. So the impeller specs are a little optimistic in relation to the motors... I will keep the current size. The well and pool are on a separate commercial meter so I don't really complain about the cost of running the pump...

 

[mas985]

It really has more to do with the ratings on the motors. Motor labels don't mean much without the service factor. Same thing applies to the impeller rating which mirrors motor ratings.