I have a Lennox 2.5 ton a/c unit, model 13ACD-036-230-05, with a blown dual run capacitor (the run terminal for the compressor is burnt off the can, the fan and common terminals are still intact, fan still running).
I had the cap replaced a couple years ago when the fan quit working. I remember the 5/45 uf, 440 volt cap that was installed was close to the original cap that failed, but not exactly the same.
I ohm'd out the compressor and got 1.4 ohms S-C, 0.9 ohms R-C, 2.3 ohms S-R. These values seem possibly reasonable to me, but according to LennoxPros, "The resistance between start(S) to common(C) is typically three-to-five times higher than run to common winding…" but they didn't state what resistance is actually expected.
What is the original cap rating (uf and voltage) for this a/c unit and what are the normal compressor resistance measurements?
Best Answer
I went through the Lennox web site to find a "store" near me and found an actual Lennox service center. They confirmed the 5/45 uf 440v dual run capacitor was correct. They didn't have any specs on the compressor coil resistance.
The service center didn't have any caps in stock but I found one at a local electrical supply house for under $10. It can also be ordered from Home Depot online (not available in stores) for about the same price.
I checked the resistance from each compressor terminal to ground (29-30 meg ohm each), re-checked the coil resistances (no change), put in the new cap, and turned it on. I noticed the current draw is lower than expected (9.2A @ startup, 8.9A running @ 230V supply vs. 15.4A nameplate) but It's working fine so far.