I have cleaned out the lines and still having the same problem of shutting off. I drain the water and it will run for a day and shut off again. I have read a answer to another post that said the installer might have installed the plumbing for the drain incorrectly. How do I know if that is true or not since I can't find any diagrams or pictures for a(12 yr old) Concord 90 high efficiency.

All condenser furnaces produce water. How is yours drained, gravity or pump?
If water backs up. It is either a plugged drain or bad pump. Water can also flow back from a poorly sloped exhaust pipe.

All condenser furnaces produce water. How is yours drained, gravity or pump?
If water backs up. It is either a plugged drain or bad pump. Water can also flow back from a poorly sloped exhaust pipe.

Thanks, My furnace is a gravity type, I'm going to check the slope of the exhaust.