Is the physical size of a capacitor important? My pool pump is making a
habit of blowing it's capacitor ever few weeks. The best price I can see on
line for this particular model is $75, however a capacitor with a similar
rating, just considerably smaller in size, is around $25.
I'm buying a new pump anyway, however I'd ideally like to get my old one
going just once more so I can clean the deep, dark green colour out of the
water before running the new pump.
So can someone tell me, as I only need it to work once, would a smaller
capacitor of a similar rating do the job?
If it is blowing the cap, check the centrifugal switch. If it hangs
and doesn't open the cap will blow.
As long as the cap is the same voltage, AC rated and MFD is the same
it will work.
I found a guy selling the cap for a 1hp Hayward pretty cheap on the
net. Shipped it was about $12 but they had a $25 minimum order so I
got some other stuff I needed.
Capacitors used with electric motors are rated by voltage, frequency, and
whether they are "Start" or "Run." Oh, and the actual capacitance
expressed in microFarads. Frankly, any replacement that "works" should be
about the same size.
As a "rule" with all other things being equal, the higher the voltage, the
larger the cap. "Run" caps are larger than the corresponding "Start" cap.
"Start" caps are switched in and our by either a special relay or by a
switch activated by the motor reaching a certain speed. "Run" caps are
permanently in the circuit when ever the pump is running.
Typically, pumps have "start" caps and there is some mechanism for switching
out the cap once the motor is running close to design speed. (Fans tend to
have "run" caps.)
$75 seems like a LOT of money for a cap for a pool pump.
You might want to look around for another vendor and get a "Run" rated cap
of a higher voltage rating but the same capacitance.
Caps do fail from time to time. If the cap was replaced with a unit with
the wrong capacitance and reduced voltage, it well might fail prematurely.
It could be that your pump has extra friction and is slowing down and
causing a "start" cap to switch in more often than it should. It's up to
you whether to spend the extra $money to keep a pump that you have decided
to replace "limping along" for another week or 2.
The physical size of the capacitor is only important if it will not fit in
The main thing is the number of MFD (microfrads) should be the same. Next
is the voltage rating. It must be atleast as large as the voltage it is
beig used at. The rating may be larger that the origional and infact may be
beter to go higher. I don't usually like to go over two or three times the
voltage rating, but woud if that is all I had handy.
If it is blowing the capacitor every few weeks, I would look into what is
going wrong. It may be someone put a capacitor rated for 120 volt service
on a 240 volt pump motor.
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