Can impeller warp from higher HP motor?

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scheiner18

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Oct 4, 2013
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I have a 4 year old Pentair whisperflo 1HP pump that quit last month. Took the pump in to local pool store that replaced the motor with a new 1.5HP motor. After about 3 weeks, I noticed a buildup of corrosion on one of the outer pump housing screws (like when a battery leaks). There is a Resilience brand salt system on the pool. As I was uninstalling the pump, I noticed it was VERY hot. Took it back in to the same pool store to figure out why the corrosion was there and they said the pump had overheated (possibly from running dry or a blockage ... neither of which sounds feasible since I know it didn't run dry and there was not an above average accumulation of particles in the pump) and the impeller had melted/warped. They wanted to replace the impeller and give it back to me.

What caused the motor to overheat in the first place? What caused the corrosion after only 3 weeks of operation? Is the higher HP motor to blame?

Thank you for any assistance!
 
Motors overheat because of one of two things. Either they ran dry or there was excess load on the motor shaft which is usually caused by a bad bearing. However, because the impeller melted, it is most likely the pump ran dry. A bad bearing would just shut the motor down after some time.

Also, a higher HP motor is not to blame and would actually run a little cooler than the correct sized motor since it would be under loaded.
 
Welcome to tfp, scheiner18 :wave:

mas gave you great feedback, and he is our expert. You could post the pump model number and the new motor model number for us to check compatibility (rated hp alone does not always tell the full story). However, as mas stated, that should have nothing to do with the impeller melting. Since the pool store seems to be standing behind their work, I would have them replace the impeller and give it another shot keeping a close eye on the pump. Corrosion might be from a bad shaft seal...but again that wouldn't cause the impeller to melt.
 
Thank you for the reply. I guess I have to assume that it somehow ran dry despite what I believe. The model number of new motor is K63CXERY-4786 and the pump is 11513. I will be sure to check the shaft seal as well. Thanks again, guys!

As a side note, I called Pentair before original posting and although they had never heard of the impeller melting under said conditions, the tech assured me that a higher HP motor would indeed run hot and would incur a degraded lifespan when spinning a lower HP pump/impeller. Frustrating.
 
Motor picture attached. Again, I appreciate all your assistance. I'm going to replace the impeller with one designed for a 1.5 HP pump (although now, in light of our thread, it seems I didn't need to do that...but it is already ordered) and try again. I'll be sure to let you know if I melt another one.
 

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scheiner18 said:
Motor picture attached. Again, I appreciate all your assistance. I'm going to replace the impeller with one designed for a 1.5 HP pump (although now, in light of our thread, it seems I didn't need to do that...but it is already ordered) and try again. I'll be sure to let you know if I melt another one.
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Don't do that :!:

The motor you listed is a "uprated motor". You need to look at the rated hp X service factor (SF) = SFHP. You new motor is 1.5*1.1=1.65 SFHP and the whisperflow 1 hp "full-rated" motor would be 1.0*1.65= 1.65 SFHP

Bottom line, it looks like the motor they put on your pump is the right one, unless the impeller was not the right size for the pump model 11513 (the one you listed aka WFE-4). Make sure you replace the impeller with the one for the WFE-4 pump!

If you put a impeller that is rated for a higher SFHP motor, your current motor will fail prematurely.

What was the model of the impeller you ordered?
 
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