AC capacitors: just 1 or 3 taped together?

Two 30's in parallel totals to 60, but if one fails by shorting (not likely), the other will also look shorted and will not provide phase shift to start the motor. If one fails by opening, the phase shift will not be large enough to start well, although it might, but if it doesn't, the motor may burn up since the high starting current has no back emf as it would if running. The 5 uF is more than likely the run capacitor.

If I had a choice, the safer option would be to use a single 60 uF. If it fails open, the motor will simply fail to start but won't burn up. If it fails shorted, then that's another story similar to above.

Do you have a circuit drawing? I am not familiar with your terminology.

capacitors in series are treated mathematically similar to the way resistors are treated when in parallel. (1/Ct=1/C1+1/C2+1/C3 etc.) Capacitors in parallel (and resistors in series) are additive, so two 30 Mfd capacitors in parallel are equal to 60 Mfd.

One thing about Capacitors in parallel, since their ESR (Equivalent Series Resistance, or the leakage resistance from one side of the capacitor to the other.) is in parallel, the total ESR for two capacitors in parallel is lower than a single large capacitor. so two capacitors in parallel should dissipate less power and they should run cooler. (and therefore last longer since they won't boil off their electrolyte so fast.). Switch mode power supplies often have multiple capacitors in parallel for this reason since the ripple currents can result in a large amount of power dissipation.

I think I'd be happy with either configuration. Especially if the guy happened to have had two 30Mfd caps on his truck but no 60 Mfd and it was a saturday afternoon in August in Texas and all the AC supply shops are closed..... Think of it as "situational electronics."

Electrically it's correct but the more components the more possible faults...

guest; usually the 5 mfd is for the condenser fan motor. perry

Now, the first company said no, it's widely accepted in the profession to use several smaller ones properly joined together

Only if your too lazy to bother to supply the correct parts. This sort of bad engineering is only good for short-term emergency repairs (remember, unlike standard capacitors filtering AC across a DC supply the motor start capacitors are in series with the winding and are passing a lot of ac current). As someone who has tested single phase motors and had start capacitors blow up on him I would not advise this, even if the two 30uF capacitors look like they are the same (and certainly not with two 30uF's and a 5uF).