Northstar died - Simply question regarding replacement motor

[sws1]

My Northstar pump died (well, it was squealing like a pig and pool guy said it was dying). It was a 1.5 HP motor / 1.25 Service Factor.

I called around and found a company that had one in stock (the pool company wanted to charge double the price I could find everywhere). They told me they had a 1.5 HP AO Smith motor in stock, but didn't tell me what the Service Factor was. One one hand, it's an exact replacement for the one I have. On the other hand, it could be an uprated 1.5 HP motor, which creates overall "power" about 30% higher.

If they do install the more uprated motor into the pump chassis, does this mean I can run my pump less, since more water is moving through the filter per hour? I currently run it 12 hours / day (25k gal pool). Could I run it, say 9 hours instead?

 

[guamguy]

Re: Northstar died - Simply question regarding replacement m

The motor has to have the same or higher SFHP as the old motor. To get the SFHP, multiply the HP time the service factor. If you want to run a lower SFHP, you'll need to change the impeller in the pump end. When using a motor with a higher SFHP than the old one, the pump will move the same amount of water that the old one did, the motor will just have a lighter load on it.

 

[Bama Rambler]

Re: Northstar died - Simply question regarding replacement m

Guamguy said it. The impeller determines how much water it'll move not the motor.

 

[sws1]

Re: Northstar died - Simply question regarding replacement m

There is a graph on the Hayward web site that implies that higher models of the the Northstar pump have higher flow rates. The only difference between the models is the motor itself. Even the impeller is the same.

I have to imagine the higher powered motor (yes - I confirmed the new motor is 1.5 HP x 1.6 SF, as opposed to 1.5HP x 1.2 SF of the old one) would spin the propeller faster and thereby push more water.

 

[sws1]

Re: Northstar died - Simply question regarding replacement m

There is a graph on the Hayward web site that implies that higher models of the the Northstar pump have higher flow rates. The only difference between the models is the motor itself. Even the impeller is the same.

I have to imagine the higher powered motor (yes - I confirmed the new motor is 1.5 HP x 1.6 SF, as opposed to 1.5HP x 1.2 SF of the old one) would spin the propeller faster and thereby push more water.

Correction. I see on the website that there is a different impeller for different motors.

SO - the original pump has 1.5HPx1.2SF with a "4010" impeller. The new motor looks like it should be paired with a "4015" impeller. HOWEVER, the repairman didn't put in a new impeller. There still using the old one. Is that going to be a problem?

See parts here: http://www.hayward-pool.com/pdf/Parts%2 ... thStar.pdf

 

[Bama Rambler]

Re: Northstar died - Simply question regarding replacement m

Putting a smaller impeller on a larger motor isn't a problem. It's not quite as efficient as a properly matched setup but it's darn close.

 

[sws1]

Re: Northstar died - Simply question regarding replacement m

Putting a smaller impeller on a larger motor isn't a problem. It's not quite as efficient as a properly matched setup but it's darn close.

Would this cause the pressure reading in the filter to be a few PSI lower? With old motor, it showed 18. With new motor and same impeller, it shows 15.

 

[Bama Rambler]

Re: Northstar died - Simply question regarding replacement m

That shouldn't have anything to do with it unless you introduced a suction leak somewhere when you put the pump back together.

 

[ianspector]

Re: Northstar died - Simply question regarding replacement m

My Northstar presented with the same symptoms after 5 years continuous service. In fact the squealing got worse and worse until the pump seized. The pool guy had the bearings replaced and it worked well for 11 months then the noise started again. He replaced the bearings again and it lasted 4 weeks. I threw it away and installed an Intelliflo. Awesome new pump and uses only 170W whilst changing the water once in 20hrs run time. By the way, I bought my Northstar in the US and paid more to have the bearings replaced each time in France.

I concluded that the Northstar is a solid bit of kit but when its time arrives it is best to take it out into the woods and shoot it and not throw more money into it. Moreover, it is not the most efficient way of moving water around.

Ian