Air conditioner condensate leakage


The evaporator coil for a friend's central air conditioning is leaking condensate on the basement floor; however, the drain line is unobstructed and also flowing water.
This is a Carrier unit of unknown vintage, and it was installed with the access panel less than a foot from the basement wall, presumably because the refrigerant connections are right below the panel, and it's a direct shot from there to the outdoor unit. Whatever, it was a real pleasure taking the panel off and getting it back on.
Could not see much with the access panel off because of the restricted view, but I did see that the copper drain line was covered with water droplets. The drain runs from the "front" of the evaporator housing to the back where the drain hose connects. Thus the drain line runs through the inlet air plenum.
Noticed a small cover on one corner of the evaporator housing. Behind the cover was a very short drain pipe with a rubber plug in it; from the factory it appears. What is the purpose of this second drain connection? It connects to the same reservoir as the other drain, but a fair amount of water came out of it when I took the plug out.
I'm guessing that the condensate tray could have a leak in it, but I don't see any easy way of accessing it short of cutting a hole in the housing. I don't know what these trays are made of or if they are are prone to rusting out.
Alternatively, I'm wondering if the uninsulated drain line, which has cold condensate flowing through it, is condensing the humidity of the incoming air and that is what is leaking out of the nearby joint between the evaporator housing and the furnace housing that it's mounted on. That's where the water is showing up when the unit is operating. The existing drain line has a trap in it so there is no air flow through it.
My first thought is to put insulation on the drain pipe inside the evaporator housing, but it will be exceptionally difficult to reach. My second thought is to plug the present drain and install the hose on the presently unused drain so that there will be no flow in the uninsulated section and no condensation on its outside surface.
What do you suggest?
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Silver Surfer wrote:

You may have a condensate pan that has a leak maybe due to rusting. Sometimes they can be replaced but a new evaporator coil may be needed. The unwrapped drain line maybe the problem but if it is part of the problem then it most likely it would have leaked from the beginning when the system was installed..
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Unless only noticeable when the weather is exceptionally humid and moisture in incoming outside air IS condensing on the cool condensate pipe as suggested. The climate is changing you know!
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Some units have a second backup drain pipe in case the first one gets blocked. The fact that a lot of water ran out when you opened it suggests that the actual drain line is at least partially blocked and not flowing freely, or there would be very little water to run out.
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On Mon, 11 Aug 2008 21:44:36 -0400, "Silver Surfer"

I had water on the floor, also with a Carrier, from 1975.
FWIW, my outside unit is directly opposite the inside unit.
Everything worked fine for the first 5 or 10 years I lived here, plus I suppose the 4 years the other guy did.
Then it started going on the floor and not into the sump.
I took off the plastic drain pipe, and blew through it with my lungs. Twenty feet but it didn't seem clogged. Still I ran faucet water through it to flush it out, and the water came out full blast. Put it back together and it didn't work any better.
I cut open the plenum to look inside. Not a lot of water, but I probably hadn't been running the AC for days or weeks before that.
Everythign looked ok inside.
I may have done other thigns but this is what worked. The plastic pipe came out an inch, then turned down for 3 or 4 inches, then sideways to the wall a couple feet**, then down to the floor 4 feet, then along the wall 6 feet, then sideways to the sump 2 feet, and down an inch.
**This piece was horizontal, not uphill.
All I did was rearrange the pipes so instead of going down 3 inches, it goes down 2 feet before it turns sideways, same distance to the wallk and then down 2 more feet or so to make 4 feet total.
Now it works fine. It's hard enough to understand why it works better now than it did, but even harder to understand why it worked fine for 15 years and then didnt' work anymore.
I"m going to post and send you a copy. If the comcast people are reading, Hi, guys!

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Mr. mm,
Thanks for that valuable information. I will give your fix a try this coming weekend.
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