Motor Run Capacitor Value

Usually they're "matched" to give max starting torque and minimum starting current (actually some happy medium on these). I'm not smart enough to figure which way does which, but you should see either a reduced starting torque or an increased starting current. I would estimate, based on my long years of burning up almost everything I've ever touched, that you would see at most about a 20% effect and that you can live with it.

Have you tried bathing her in the spring? That's when I do it, usually around April 1.

Have you tried bathing her in the spring?
Oooh you don't mess with Mrs Cat first thing in the morning.

The pump only runs for a few seconds at a time so I guess it will be fine. When I opened it up last night (not a pleasant job as the sump box thing was full of stale smelly water) I opened the top of the actual motor case and was surprised to find it full of oil...well nearly full cos I spilled a fair bit. 'Oh dear' I said... It's quite a nicely built unit all tightly sealed, I s'pose the oil filling helps with heat dissipation and lifelong lubrication.
It was deffinitely the cap' which had gone down..I measured it at work this morning...zilch microFarads, so if you want a 0.0uF at 450v, I have just the thing
I shall rebuild it tonight.
Del

Del-

The primary purpose of the oil is to keep water out of the motor...if you spilled some, you really should try to top it off. Of course, housing is never submerged above the sealed seam, then it won't matter much...

It will unbalance the magnetic field use to start the motor direction. The start windings magnetic field are incorporated into the run winding field as they are always there. May cause the motor to over heat. Or produce poor performance.

Ta.
I've ordered a correct value replacement, so if there is any sign of an adverse effect I'll change it...prob' is the right value one won't turn up for a day or so.
Del

IF you have ever looked at at typical motor run or motor start capacitor the better ones have the tolerances stamped on them. Most say -20% to +50% of the rated number.

8 uf over 6.3 uf is well within a normal working tolerance. Electric motors are not all that fussy about this stuff.

Woo hoo, bish bash bosh, job's a good 'un.
Mrs Cat's happy, so were all happy, right?

Del

MEOW !!!

It will simply work....

The only point to watch out for is that there are two (at least!) qualities of start caps. One is designed ONLY to start and a centrifugal switch in the motor cuts it out when running, the other higher quality stays in circuit and gives the motor more torque while running.

The ones for continual usage can be used in either motor, the start type only not.

It could be that the cap is defective because the motor centrifugal switch is not disconnecting as it should......

He said that it is a RUN capacitor, not a START capacitor. There shouldn't be any centrifugal switch.

Del, make sure that the replacement capacitor has a higher or equal voltage rating. The exact capacitance is not so critical.

Hi did, but I have seen so many people mistake one for the other. So I like to be very accurate and try to cover all/both bases......and be safe.....

Have a great day!

Dell,know that operating behaviour of capacitor motors depends on size of the capacitor.The higher the capacitance,the greater the starting torque.

At very high capacitances,the current in the auxilliary winding rises to very high level,thus causing overheating.So u have to watch out time to time to be sure the motor thus not overheat.In some cases,the capacitor could be cut off after starting,to avoid overheating,especially where u have auxilliary cap-Ca.ofcourse u can design to cut off Cb after starting yr motor as well.Depends on yr design based on how well u understand the circuit.

However,i hv replaced a 2.5μF cap with 3.5μF and it wrks fine,no excessive heating.So,yr 8μF may do the job with a greater torque than 6.3μF.Get a close value,say 6.5μF-7μF.8μF is not too critical a value,i dont know if its within range,but watchout for increased current and undue overheating with time,pending when u get the right replacement value for a longer life span of yr waste pump.

Going up in value,increases starting torque,increases current in auxilliary winding as well as causing overheating.overheating weakens yr coil gradually with time and may reduce performance of yr motor.

Going down in cap value reduces starting torque,poor performance of yr equipment and could likely heat up yr coil too if it stays longer.In some cases,it will not even start yr motor or equipment if the value is too low,far out of range.

The best is using the appropriately rated value(6.3μF) used in the manufacture of the equipment or written on the data or name plate of the equipment.This will give good performance,long life etc,as long as you do normal maintenance service on it.

Dont forget to check the rated current of the moyor,former operating current with the 6.3μF cap and the present operating current with 8μF cap.Ofcourse Mrs Cat wouldnt take it easy with u,if it fails in the long run.

Patrick Whowha

Cheers, I actually measure the 8uF cap and it was only 7.5 so I'm not too far out.
It only runs in short burst even when Mrs Cat is showering. It runs in a burst to empty the sump then waits for a bit. The shower only runs a couple of times a day.
Del

A run capacitor is in the motor circuit at all times when it is running.It is responsible for the phase shift that allows the motor to self-start and run.No centrifugal switch needed.A start cap is usually much higher value,100 to 250 or more MFD.A severly mis sized cap can cause the motor to overheat or stall.Sounds like you are in the ball park, but an ampere reading of the run current compared to the namelate data would be informative.The lost oil should be replaced,and the motor sealed.It cools and insulates the motor and provides a moisture barrier.

HTRN