Speaking of evaporator coil drains, it appears my main drain pan in my A/C coil in the attic is rusted thru and the condensation is leaking into my secondary pan. Just what I need....a 15 year old unit go south and the system is R22.
I know that replacing the inner pan is a pain as it is part of the coil housing.
Bummer! We have two A/C systems also attic mounted. The originals were true horizontal units, I replaced the one for the big part of the house at the 22 year mark. The horizontal evap coil cabinet had a vertical-mount flat coil in it. Later when I looked at the pieces I pulled out, the drain pan and the bottom of the case was just a rust mess. Surprised it hadn't leaked. With its flat-coil design, it would have been possible with some galvanized steel to repair and replace the pan and its supports.
Both replacement systems I installed are actually gas basement upflow furnaces and A-coils, but laid down on their sides. I lucked out in that the guts were installed at the factory so they could be laid down on their left sides, which is the way I needed. Otherwise, I would have had to unbolt everything inside and flip it over.
Unfortunately, I don't remember how the side drain pan for an A-coil that can be laid on it's side is attached, as to how difficult it would be to replace it in the field without discharging the system.
For an A-coil cabinet, there is usually a sheet metal access panel in the side of the cabinet that can be removed for coil cleaning, that would allow a peek inside, to see where the drain pan in use is, and how it is fastened, if it is a separate pan, and not integral with the bottom of the cabinet.
My bigger unit has a separate white plastic pan, and the white plastic can be seen where I attached the PVC pipes to for the drain line.