Replace pump motor with dual speed?

[Brandoga]

I have an old 1.5 HP single speed high-flow Centurion motor on a CHII-N1-1 Pac-Fab pump. The motor has always been too big -- designed for a water feature that we never added. Pool equipment guys have told me it is oversized for my 25,000 gallon gunnite pool and 62 GPM sand filter. I've kept up the pool easily with the TFP formula, even though the main drain has never worked (2 skimmers, 2 returns) I've kept the pump maintained with occasional part replacements, and it's held up well for 18 years. I'm finally upgrading -- adding a SWG, and I'd also like to replace the motor with a smaller, dual-speed model with a manual switch. I have a couple of compatible part numbers for a 1 hp and 1.5 hp pump from Inyopools, but they keep pushing variable speed models. Any advice? Can I use the smaller motor, or should I stick with the 1.5? Suggestions appreciated.

 

[jblizzle]

You can only use a smaller motor on your existing pump if you also install a smaller impeller that matches the motor. Otherwise you will burn up the motor. The same might be true for a VS motor.

I started off with a 2-speed manual switch on my Superflo until I added a ProLogic Automation setup which now changes the speeds for me.

 

[Brandoga]

Thanks for the quick answer - I don't understand much about matching the impeller. Does that mean, though, that I can swap out the same size motor (1.5 hp) for a dual speed of the same rating?

 

[jblizzle]

Yes. You have to look at the HP and the SF (service factor) on your existing motor. Multiply them together. And make sure that the HP*SF of the new motor is not less than the original motor, it can be higher on the new motor, but will not pull more power as it is hooked up to the smaller existing impeller.