+/- 5% deviation in capacitor ratings

[laszlo]

I have several 15 mF capacitors for a compressor. Measured several of them, and they come in at 14.5 mF.  Never at 15. 14.5 mFarad is within the +-5% deviation, but I am wondering if there is a pattern, ie.: this is some way to save materials for manufacturer, or maybe this is temperature related?

[boB]

Yeah, capacitors ALWAYS seem to be on the LOW side !

It's a specification numbers game I'm pretty sure.

[TomW]

Yeah, capacitors ALWAYS seem to be on the LOW side !

It's a specification numbers game I'm pretty sure.

Back when dinosaurs roamed the Earth and I learned this stuff my feeble memory recalls many components were actually +- 20%.

I am pretty sure it is a numbers game. a few square meters of foil & insulator over a run of a few million capacitors probably saves enough to "justify" a target value below rating but within what they call manufacturing tolerances.

Or not.

Tom

[boB]

Yeah, capacitors ALWAYS seem to be on the LOW side !

It's a specification numbers game I'm pretty sure.

Back when dinosaurs roamed the Earth and I learned this stuff my feeble memory recalls many components were actually +- 20%.

I am pretty sure it is a numbers game. a few square meters of foil & insulator over a run of a few million capacitors probably saves enough to "justify" a target value below rating but within what they call manufacturing tolerances.

Or not.

Tom

Yes, I also seem to remember specs something like  +5%  -20%  on electrolytic capacitors.  Might have been +10 %  but it was lop-sided.