Finally figured out why my Carrier unit was dripping water after shutoff

I had the same scare last August with my Mitsubishi Heavy Industries unit. Living in South Florida, the humidity is basically soup most of the year. I saw a decent puddle forming under the wall bracket and convinced myself the drain line was backed up or the R32 was leaking. I even climbed up a ladder with a flashlight at 11 PM to inspect the service valves because I was so paranoid about a repair bill. What I found was exactly what you described—the 'sweat' was mostly on the base pan and the underside of the compressor housing. I actualy used a kitchen thermometer to check the casing temprature, and it was sitting at about 54 degrees while the ambient air was 82 with 90% humidity. That temperature delta is a recipe for a mini rainstorm under the unit.

I ended up adding a small piece of foam tape to one of the vibration pads because the water was pooling in a weird spot and making a constant 'plink' sound on my patio cover. As long as the water is clear and not oily, you are usually in the clear. Now I just ignore it unless the air stops blowing cold.

My experience with a Daikin split system was acutally the opposite. While the OP is right about the metal casing sweating, I found that my 'condensation' was actually a clogged drain line that only started backing up when the humidity hit 85%. I kept ignoring the puddle on the patio thinking it was just external moisture, but it turned out the internal tray was holding about an inch of stagnant water because the installer didn't quite get the pitch right on the PVC pipe. I ended up using a shop vac on the exterior outlet and pulled out a massive 'snot' plug of algae. Now, even on the stickiest nights in Houston, the chassis stays relatively dry because the internal drainage is pulling that moisture away fast enough. If you’re seeing more than a light mist or a few drips, it might be the tray overflowing rather than just physics. I'd definatly recomend checking that the drain is actually flowing before assuming it's just the casing equalizing.

Have you guys actualy ruled out a gap in the armaflex insulation where the lines meet the service valves? It’s easy to blame the chassis sweating on physics, but if that insulation isn't taped tight, you're getting heavy condensation right on the brass. I’d also be skeptical about the 'it’s fine' mentality unless you’ve checked the level of the unit. If it’s tilted even a few degrees toward the wall, that condensation can track back along the pipework instead of dripping off the pan. It might look dry by noon, but have you looked for salt tracking or water marks on the bracket itself?

I ran into this with my Panasonic unit last summer. The sweating was driving me nuts, so I actually bought a cheap plastic drip tray designed for window units and rigged it under the wall bracket. I piped it into the main drain line with some vinyl tubing and zip ties. Problem solved. Now the water actually goes into the garden instead of making a slippery mess on my walkway. If the 'physics' of the sweat is normal, just manage where it lands so you don't have to look at it.

Spot on about the R32 units. I’ve seen this time and again with the Fujitsu Halcyon series too. People forget that those inverter compressors, like the ones in the 12LZAS, keep the refrigerant circulating at variable speeds even during a soft ramp down, which keeps that base pan freezing. If you're relly worried about the runoff, check the discharge temprature with a thermal camera. If the casing is hitting that 50-degree mark in high dew point zones, you're going to get rain. Just make sure your flared connections aren't the source; if that condensate looks oily or smells like a workshop, then you've got a real problem on your hands.