ok.. here is the scenario..

an above ground, fairly new, but seemingly low-end, jacuzzi with a cap run/cap start motor powering the jets. 240v. Problem is the motor buzzes like and angry hornet while
turning over and never properly kicks over, but only tries to spin, moving very very slowly,maybe 8-9 rpm. My first thought was a frozen impeller in the pump. so after
removing the motor and finding the impeller was flawless and that the motor
rotated freely without any impediment, I hooked it up to 240v and it seemed to
run fine with no load. Reinstall motor, add water to the plumbing and again,
buzzing and no appreciable rotation. My next thought is, ok, burned out start
capacitor. Ordered new start cap with specs identical to the original, install
the new cap, run the jacuzzi.. and when it came time for the motor to kick in,
it kicked in and ran fine for ~2 minutes, then the capacitor got hot, smoked
and leaked dielectric goo out of the case.

Now I am stumped. The motor seems fine, although I have no idea how it has
been used in past lives by previous owners (possibly overheated? and for how long?). This thing was acquired second
hand by its current owner (not me thank god) so I have no idea when this problem
first occurred. It had been sitting idle and unused for some time at the home
of its previous owner, so maybe that plays some role. I was called in by the
current owner because after having brought the thing to its new home,, I ran
pipe, wire, etc. to get it properly connected, at the moment of truth the
jets/pump didn't work. It has an electronic control box, wired to lo-volt
waterproofed controls "up top" that you can operate while immersed in the
jacuzzi. When the controls are set, the motor is getting a full 240v out of the
control unit. Faulty control box was one of my suspicions, but it seems not.
I am now reduced to one of two suspicions.. faulty cap or damaged motor. Can
anyone make any sense of the symptoms as I have described them? I am truly
stumped at this point. The behavior of the thing seems to indicate some damage
in the motor, but none is apparent. Any suggestions for tests that can be done in the field, to
quantify any problems would be appreciated..

It sounds like the centrifugal start switch is not kicking out when the motor rpm increases.The centrifugal switch disconnects the start cap and start windings from the circuit when the motor reaches a certain rpm.
The swith contacts may be fused. This would would fry your cap as you described and will eventually destroy your start winding as well.
I am no motor expert but thats my best guess considering your description.

rpms never get high enough for a centrifugal switch to kick out. I could spin this thing faster turning it myself with a crank...

How well does the motor spin when it is all put back together? You should be able to spin the shaft with a screwdriver or nut driver from the wiring end (depending on what holds the centrifugal plate on.) You can't spin it fast enough by hand to actually feel any head, even ful of water.

you can megger the motor to determin if its good or bad(you should see at least 4 or 5 Meg ohms), beyond that from what I understand the motor and cap came as a package together from the manufacture but never the less I would call them and verify the charge and discharge curv values of the cap needed and make sure thats what you have, to at least eliminat anything wrong there,
by the way what size wire is feeding the motor and whats the distance from the panel? (Im thinking voltage drop issues) dose the motor have the ability to be wired for 120V & 240V if so are we sure its not wired for 120V?
process of elimination Trollog youll get buddy good luck.

Hey Trollog

You mentioned that you changed the start cap and then the motor started and ran fine for 2 min. before the new cap got smoked again.
If the centrifugal switch was fused the new cap would go up in smoke. Then when you tried to start it again it would be doing what you describe simply because the new start cap is smoked.
Just a thought but might be worth exploring.

I second that idea that the centrifugal switch is fues closed...I've had quite a few projector motors go down in flames because of that.

Changing that switch isn't too difficult and the part is usually not too expensive. Check out Grainger's, they have the parts in stock for most motors. They may also have a replacement motor (use the Dayton brand, good value) which may be worth it in labor savings.

Keep us updated..

Yes, the centrifugal switch will be the next thing I investigate.

All the other variables.. voltage, wire size, distance, etc. I already planned for and did right the first time. For the record, the motor is getting 242v out of the power supply, so I know it doesn't have anyting to do with the power supplied to it. Don't know why a centrifugal switch didn't occur to me sooner. But then that's the value of this forum.. great sounding board when my thinking is muddled or immovably stuck in some rut.

Will do on the updates, and I will get some pics of the pieces/processes and damage, for whatever educational value may be in it for others to see real world examples of whatever damage it turns out this motor has..

Good idea Ryan,

A centrifugal switch is supposed to open at 75% full-load speed of the motor.
Might pay to check that the actuator for the centrifugal switch is moving freely, they can freeze up through lack of movement over time.

Although is sounds like a cap problem, with all the abuse is has recieved, the customer my be dollars ahead by replacing the motor. Everytime the motor is energized and does not spin properly, you will have aged the brushes and rotors. This will lead to pitting which will lead to crud and corosion within and the motor will die an early age. It is likely what it was a nearly new tub. The previous owner had problems with it and got rid of it. Did you also check the taps in the motor to ensure it tapped for the voltage?

sparkyinak:

There are no brushes in this type of motor. Purely induction