A/C Capacitor Voltage

No,

The 440/370V cap is actually just a 440V cap.

I assume your system is running on 240-250VAC in a residential installation? If so, the 370v cap is fine, but I prefer the higher voltage ones as they should last longer.

I assume the "uf" rating on the new cap is identical to the old one? That's important. Something like, 5uf?

TL;DR: it's probably fine. If in doubt, get the higher rating.

Compressor, fan, dual? If you went to the supply house & they looked it up from the unit model & serial, I would imagine that's the right one. If you just crossed it over from the existing, I would've expected a 440 volt one, or dual rated. Like @ChrisJ and @EdTheHeaterMan said, a higher voltage rating will substitute for a lower—but not vice versa.

It's my understanding that the motor design determines the voltage of the cap. (I read that on the Internetz some time in the last few decades, so it must be true!) In any case, you can verify the voltage by simply measuring the voltage across the cap with the unit operating, it'll be around 370 volts, or it'll be around 440 volts. The outdoor fan motor and the compressor both should have a nameplate that specifies the capacitance and voltage of the required cap. Two separate ones work the same as a dual. Oval vs round is merely mechanical, you can use either if you can get it tucked up in there somewhere.

IDK either, but the ol' memory banks keep coming up with the same thing I said earlier. I think it was a motor manufacturer's website so I put a little more confidence in it than if it was from some rando blog. I did measure one once & found 37something. Slightly over the actual rated voltage, but I know from experience that they are reasonably reliable.

When it comes to Capacitors for HVAC repair I stopped stocking 20 different dual and 15 different single caps in favor of the Turbo 200. Three of those per truck and one of the larger Turbo caps greatly reduced truck inventory costs and space. I can also offer a 3 year warranty on them because Turbo offers a 5 year warranty. I just need to cover the labor portion. That Turbos are all rated at 440 and you can build the exact uf you need. I know that they are more expensive that the ones made of chinesuim but the warranty suggests that they will last longer. A better deal for the customer that is paying retail for repairs.

That's why I never dug too far into it.

I just automatically buy 440v caps, regardless, specifically Titan HD which say they're made in USA.

The life of an electrolytic cap is a function of voltage and temp. It will work a bit above its rated voltage for quite a while but won't get its rated life. You can get more life by using a cap with a significantly higher voltage rating than the working voltage.

Most caps are rated wvdc. Motor caps are rated v ac. I assume that is to deal with the peak vs rms in ac voltages and that people dealing with motors are bad at math. Motor caps are special in a number of other ways too because they are carrying significant current and I think they are also bipolar. Run caps have to carry a continuous current, start caps just have to carry that current briefly.

I was just wondering if everyone knows what uF stands for?

That symbol is not actually the letter "u" but the greek letter µ pronounced Mu like you might here a snobby cat from the upper east side say MEOW. The µF stands for Micro Farad and is sometimes labeled MFD or mfd. So… µF, uF, uf, mfd and MFD all mean the same thing depending on the letters available on your typewriter. But never say "you eff" for Micro-Farad because that is totally wrong. Always read uF as Micro Farad

That is the concludes todays Greek Lesson.

Just to recap (sorry). You can safely use a capacitor with a higher VOLTAGE rating than required. No problem. You can NOT use a capacitor with a capacitance much more than 10 percent higher or lower than required.

The OP said his old cap was rated 370/440.

Not sure I have ever seen a cap with a dual voltage rating.

A lot say that now. I think the Titan HD ones do as well. They're just 440v caps.

I've seen capacitors rated for all kinds of voltages

16, 35,50,63,75, 600 etc.

Try to look and see what the motor says on it. If the label is still legible it'll tell you what it needs.

Or buy a 440v cap online and swap it out and you'll know it'll last. Make sure the "uf" spec is identical.

There is only one downside to choosing a higher voltage rating (within reason!): it may be physically larger. There are a lot of upsides. One of the more important is that a capacitor with a higher voltage rating is more durable — both in terms of resistance to the odd voltage spike but also in sheer longevity. Now as you get into really high voltage ratings — upwards of several thousand volts — cost begins to rise as well.

In same electronics applications, the type of capacitor may matter as well, but not in motor starting or the like.