Single speed to two speed pump conversion

[dschlic1]

We currently have a single speed 1.5 HP pump on our pool. There are several good and valid reasons for having this size pump. However this pump will change the water in the pool in 1.5 hours. I will need to run it for most of the day because we have a SWG. For this reason, we would like to have a two speed pump.

My first thought was to see if I could replace the motor stator. However the motor manufacturer, A.O. Smith does not offer the stator as a spare part. That meant I will have to replace the entire motor, which is not a big problem.

The pump is a Sta-Rite model, and I looked at the differences in parts between the single speed and the two speed models. I noticed that the impellers have a slightly different part number. I e-mail Pent-air (contact for Sta-Rite pool products) about the difference between the impellers. They replied that for the conversion the impeller needs to be changed, however they did not know what the difference was.

The question I have for the forum is has anyone seen the two impellers and can they tell me the difference? Or should I just try changing the motor?

 

[mas985]

Usually the impeller is matched to the motor. If the braking HP (Label HP * Service Factor) is the same between motors then the impeller should work fine. If it is not, then you may be better off getting a matched impeller as well. Otherwise, you could over or under drive the motor.

 

[klondrie]

2 speed pump motor

I have a 1.5 hp pump motor on my pool with a SWG and the slower speed will not work when I run it on low speed. I have tried it with and without the solar panels in line. Hope this helps

 

[dschlic1]

Klondrie why did the SWG not work on low speed? Was the flow too low and the flow switch not activate? Or did it not generate enough chlorine?

 

[klondrie]

SWG flow

The flow was too low to activate the SWG. I recently purchased a flow meter, (which will be installed next season) To try and determine the flow rate on low speed. This is even without running the solar panels. If anyone has had a different expierence and can run on low speed with a SWG, (mine is an Autopilot-60) Or knows approx flow rates for the SWG, please chime in.

 

[dschlic1]

I have a Goldline Aqua Plus unit (the same as the Aqua Rite units). I e-mailed technical support on the min flow rates for the cell. It appears that the cell it self has not min flow rate, however the associated flow switch operates at about 11 gpm. So if at low speed the flow rate is above 11 gpm, my SWCG should work.

My Sta-Rite model P2RA5F-182L pump produces about 80 to 90 gpm at the pressures I am encountering. So if I half the speed, this should give me a flow rate about 20 gpm. I have been unable to find a pump curve for the two speed model at the low speed.

 

[mas985]

Actually, half the speed is half the GPM so you should have about 40 GPM.

Also, you will have about 1/4 the head loss and 1/4 filter PSI.