Furnace & AC Capacitors

Match the microfarads exactly and never round. The µF rating is tuned to the motor's start winding, so a 45+5 can replaces a 45+5 can and nothing else — "close enough" is a motor running hotter than designed for every hour of its remaining life. Voltage is the one number you may go up on: a capacitor's voltage rating is a ceiling, not a target, so 440V safely replaces 370V in any application. Never the reverse.

Dual or single is decided by your cabinet, not by preference. A dual can carries two capacitors sharing a common terminal, serving the compressor (HERM, the larger value) and the condenser fan (FAN, the smaller) from one housing. If one section fails you replace the whole can — that is not a manufacturer's trick, it is what "one housing" means. Two singles wired to a shared common do the same job if you have somewhere to strap them.

Round or oval is purely mechanical: the strap on your unit decides it, and the electrical spec is identical. Rated life is quoted around 60,000 hours at rated ambient, which is roughly ten cooling seasons — but nothing about the inside of a condenser cabinet in August is rated ambient, so five to eight years is the realistic field figure. Units in direct sun or with restricted airflow run at the bottom of that range.

Buy the contactor at the same time. The contactor and the capacitor sit in the same cabinet, cook in the same heat and accumulate the same run hours, which is why they fail together 41% of the time in our own order data. If the panel is already off, the second part costs you a screwdriver turn instead of a second afternoon.