New furnace leaks when heating, not cooling.
I'm bought and had installed a new central furnace/ac unit. It is a high efficiency furnace at I think 95%. I have had it for one month. All was fine while I was running the air conditioner. I could see the water running out of the hose into my sump pump. The other night I turned the furnace on as the wife was chilly. It came on and heated just fine. I went down to admire my investment and there was a pool of water around it. I opened the bottom of the unit and seen water dripping from the housing of the blower fan and the bottom of the unit had quite a bit of water standing in it. I called the people out to check it out. He told me the drip tray needed adjustment and the raised the drain tube up about an inch to allow a downhill run for the water. After they left I turned the furnace back on and within half an hour there was water running from above the blower fan and down around it and dripping back to the floor again. I turned the A/C back on to cool the house back down and the drip went away. My thoughts are that if it was the drip tray it would drip more with the a/c on than with the furnace on and that the problem is somewhere in the heating system, not the coils or drip tray.