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Start Capacitor Questions

1K views 3 replies 4 participants last post by  Mycrossover 
#1 ·
Hi


I have a couple of questions for you guys.


1) In the picture below of the two capacitors, can I use the newer capacitor with a 270-325mfd to replace the older one that is 216-259mfd? Both are 110vAC.



2) How do you tell which side is positive & which is negative on these capacitors or does it matter? If it doesn't matter then question 3 doesn't need to be answered .



3) As I was removing the cover for the capacitor the wires going to the capacitor popped off and the connectors fell apart before I could see how they were connected to the capacitor. How do I tell which wire goes to positive and which one goes to negative, "both wires are black"?
 

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#2 ·
A capacitor is often marked where the negative is like a car battery is marked. If not if it has one connection closer to the outside that one would be negative.

I would keep the mfd as close as possible when changing them out. Think of a capacitor as a battery and the larger the number the more power. A capacitor stores electricity so it can give the motor an extra kick at start up to get it turning. Too much kick and you might damage the motor.
 
#3 · (Edited)
It makes no difference which wire goes to as long as they both are on


It is a good idea to replace with the same MFD if not try to get close, the one you have is a little high but it would work


A start cap works by shifting the start and run windings farther out of phase to get more torque on start up, as the motor accelerates you will hear a little click that is the centrifugal opening and dropping the cap from the circuit, and you will hear it again as it coasts down closing
 
#4 ·
They even sell capacitor kits with potential relays that can be wired to a motor that already has a start cap but needs a little more help. Going a little bigger is an old trick to boost start torque. But if you have no start problem with the original value I would stay with that value or a moderate increase.

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