pump motor overheats

[Poconos]

Still laying in bed laptopping. I know...LAZY. One of the retirement perks. Going to be the last of the nice, warm, sunny days for a while here in the North Pole. Then snow later this week. Bah. Old backup pump is already set up to externally circulate water, and I like to play with water. Me feels an experiment happening a little later with suction side blockage. MAS may be on to something with the impeller but I doubt bad bearings would cause this. With enough drag on the motor to heat it up, the bearings would grind up real quick and you would need hearing protection.
Al

[matt4x4]

Did you verify that the motor and wet end are matched up, it sounds like the motor and impeller are mismatched - a common problem when not replacing the motor with an identical unit - HP is not the only spec in the equation. Seeing that it's draw is only 4A with no load, it looks like it's trying to push too much volume once under load, straining the motor - this could be because of a mismatch between the inpeller and motor.
You did not state whether the original motor was replaced with an identical unit, only that hte replacement was replaced with an identical unit - this is what's leading me to believe you're dealing with a mismatched motor.

[pmdelage]

Sorry I wasn't clearer. The motor that quit was a 1HP with, as it turns out, a 3/4 hp impeller. Took the impeller to the pool warehouse and proved that it was a 3/4 hp by comparing it part # and physically to a brand new 3/4 hp impeller.
Parts folks said they could see nothing wrong with impeller.

Pump is an Ultra-Flow and the diffuser is good from 1/2 hp to 1 1/2 hp. Both 3/4 hp motors exhibit same problem, high amps, high heat, cut out operates. Voltage while pumping is 238 at motor. New pressure gauge indicates 8 psi at filter.

We are trying to backflow suction lines. May have to find a pump to really get some flow in the lines as garden hose may not hack it.

[JohnT]

Have you tried running the filter with the valve set to waste to see if the current draw changes or if the overheating problem goes away? Setting it to waste would eliminate a restriction (if there is one) where the new SWG was installed. When something fails and is replaced, often there was something else wrong in the system that either caused or accelerated the failure of the part.

[mas985]

It sounds as though the impeller may be for a 3/4 HP full rated motor or a 1 HP uprated motor, they are typically the same. You may have chosen a 3/4 HP up rated motor for which the impeller would be mismatched.

What is the service factor of each motor, including the old one?

What is important is to match the HP * Service factor.

[Poconos]

For what it's worth. It appears as if restrictions on the suction side have the same effect on current as a restriction on the pressure side. Best I could do was plumb a ball valve in the suction side and start restricting it and watching the current. If I restrict it too much the pump basket starts getting sucked dry so I avoided that. Adding just a little restriction indeed dropped the current. The jury rig I use is airtight. Verified that years ago when I first started using this old pump to circulate before de-winterizing the real equipment. I always have air in the suction side and I think what's going on is air is coming out of solution under the vacuum. I see this more with colder water which makes sense. I can only easily use 1.25" pipe so that's a slight restriction right off.
Pump is an old Jacuzzi 1 HP SF-1 240V configuration
Running dry -- 3.7A
Full flow (best possible) -- 5.0A
Slight restriction -- 4.6A and down from there.
Al
Attachment 662