Pac Fab Challenger with New Variable Speed motor primes but no pressure

[Cmasty]

I recently purchased a new variable speed motor from inyo pools (they were very helpful in getting me with the right model for my pump) . I installed the motor today and got it all wired back up and in place. Old motor was 1.5 hp uprated to 1.65 and new motor is 1.65 hp at full speed.

I start the pump and it primes no problem, however my pressure before putting in the pump was ~15psi and now wont come up above 7psi. It seems weird that it will prime but wont pressure up with motor running at 100%. Any thoughts?

 

[kimkats]

How does the pressure at the return feel?

Do you need to back wash the filter?

Does your gauge drop to 0 when the pump is off?

You might have a new "normal" with the pump. We will find out.

Kim

 

[CJadamec]

If you have the same wet end and are spinning the same impeller then the pump curves wont change. The pump will move the same amount of water for a given rpm. As long as the new motor is spinning at the same rpm as the old motor at full speed nothing should change.

Other than the pressure gauge being off do you have any other signs that something is off like return flow, weird noises from the pump, signs of suction leak?

 

[Cmasty]

I have backwashed within 1 week of motor change and did backwash with weak pressure after the motor change -- to no avail.

I'm fairly certain its not the pressure gauge. Previously, I could open the filter vent and it would spray water about 20' at 15psi and I couldnt seal with my thumb. It's at 6-7 psi now and i can easily cover the stream with my finger and keep it sealed. I can also tell that the water is moving less vigorously in the pump basket because of a large difference pre/post new motor. The pump does prime however, and is making water move as presented by the returns in my pool. The pressure is just 40% of what it used to be. Same RPM, Same HP.

 

[CJadamec]

HP is meaningless in this problem unless the motor isn't spinning at full rpm because it doesn't have enough hp.
Pump output is directly related to impeller rpm. Since you installed a variable speed motor are you sure you have the motor spinning at the right speed? Were the diffuser and impeller in good condition and go back in correctly when you put the pump back together?

 

[Cmasty]

Same RPM. Pump is on override @ 100%. Impeller looked fine. I'm going to take it apart again and see if the impeller is fouled by debris.

 

[CJadamec]

Make sure the defuser and wear ring are seated properly and not worn while you are in there inspecting the impeller. Double check all the parts are back in place in the right orientation.