my fellow tech said it makes a difference to compressor operation, which voltage run cap you use. i say that voltage stated on the run cap is it`s dielectric limits, and the microfarads in new, should be same as old, at usual 208v to 240v conditions.
You are right. The voltage is just a maximum operating voltage and has nothing to do with the function as a capacitor. Operating within its voltage limits, any capacitor with the same MFD value will perform the same.
The voltage rating on a capacitor is the voltage limit of the capacitor. Exceeding the capacitor's rated voltage may cause the dielectric to break down and the capacitor to short out.
That said, you need to realize that a motor is an inductive device. When you the supply voltage is applied to the motor run winding, the voltage across the start windings will be increased to a higher voltage value. A motor acts like a transformer with the run winding acting as the primary and the start winding acting as the secondary.
This is why the capacitor has a much higher voltage rating than the supply voltage.
sopositly you can go up or down 5% but i always put in the same size mfd but only use 440v caps
less to carrier on the truck
5mfd and 7.5 mfd 370v and 440 v on truck
Had a blown up cap today at 5pm. It was a 40/3 370V cap and I didn't have one on the truck. So I took 2 10uf, and 4 5uf, and linked them with a 3uf so I could get them a/c until I could get the right cap. It was ugly and I had to strap it under the electrical box but it works.
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I would rather use the correct mfd than volts in an emergency.
