re: Capacitors

quote:

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max voltage # needs to match

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Just to clarify, you can see some capacitors that state 370V-440V. What that really means is it is a 440V Max volt capacitor and it will also replace any other AC condenser fan capacitor under 440V. A 440V Capacitor can replace a 370V capacitor, but if a system really needs a 440V capacitor, then a 370V capacitor cannot be used to replace a 440V capacitor. It was confusing to a lot of people in the past that a 440V capacitor replaces 370V capacitors so some manufacturers stamp 370V - 440V on what is essentially a 440V capacitor.

It is critical to match the microfarads for a replacement capacitor and to get a protected capacitor if the one you are replacing says it is protected. A capacitor that is stamped +-5% is better than one than one that says it is within +-10%. In fact if you test a capacitor you should replace it if it is outside of a 10% range. They usually lose capacitance over time, so as an example a 40 mfd run capacitor that drops to under 10% (under 36 mfd) should be replaced as the capacitor is now providing less current to the condenser fan and compressor than is in a normal range. I just recently replaced a 40 mfd run capacitor that was the problem. My multimeter measured the existing capacitor at 35.2 mfd which is too low. I replaced it with a new capacitor that measured 40.7 mfd with my multimeter. That fixed my problem.

Capacitor size and shape do not have to be an exact match although generally if you have a round cylinder shaped capacitor you would replace it with another cylinder shaped capacitor that otherwise has the same specs. If the diameter is larger or smaller you will have to adjust the bracket or galvanized pipe hanger strap that secures it.

It is also nice to have a decent multimeter on hand that tests capacitance so that you can test existing and new capacitors to make sure that they are in +-10% of stated value. As always, treat any capacitor like a loaded gun and make sure you know how to safely handle them and discharge them or get an HVAC Tech to do the work.