Originally Posted by suzy
50/7.5 capacitor with a 50/5.0 one as well as the fan motor.
The old capacitor registered 4.8,
is this 5.0 really enough for this unit?
It becomes a question of likelihoods. The guy might have gotten lucky.
If the 7.5 had a tolerance of +/- 50%, the value can be between 3.8 uF and 11 uF 95% or 99% of the time, depending on the quality control of the capacitor manuf.
Probably 4.8 uF does not work if his diagnosis was correct. Without looking up the Normal Distribution curve and all thathttp://en.wikipedia.org/wiki/Normal_distribution
about 1/6th of the 5 uF caps that he picks at random will work in this application.
When you add in that the 5 uF also has a tolerance, this 1/6th becomes less.
He might have gotten lucky. And if that cap drifts off of 5 uF in the wrong direction it will fail sooner than one whose value is centered on 7.5 uF.
It was probably late in the day or he was tired.
On second thought -
In a way, there is a contradiction here. If the design center value is 7.5 uF and he declares 4.8 uF to be unacceptably out of tolerance then he should not turn around and replace the 4.8 with a 5.0. He might as well have left the 4.8 in place.
So my first objection was on the grounds of bad practice, and my second is that he is contradicting himself. I hope you at least got a good price.