I've recently replaced my central A/C system and now ended up with some motor run capacitors from the old A/C. (I tried to salvage the relay, but it's already worn so it's no good.) My question is, will a motor run capacitor withstand a direct connection to the mains for a long time? I think that one connected in parallel with the input of a UPS will help absorb electrical noise and help prevent nuisance tripping. The capacitor I'm planning to use is 5uF, 370VAC. BTW, is it possible to use a capacitor as a ballast for a fluorescent lamp?