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This picture shows furnace flue condensation problems. This problem is caused by hot gases cooling too quickly in the flue. As the hot gasses cool, the moisture in the gases condenses and starts dripping back down the flue. Typically, there is a combustion issue or bad flue design.
Flue Condensation Problems
See the related furnace flue videos below
This problem can be solved by making sure the gases are hot enough to be vented into the atmosphere. Vented up the flue before the moisture condenses in the gases. It could be a problem that requires a slight adjustment at the burner. Furthermore, it is a good idea when you observe a furnace flue condensation problem where the condensation is dripping back down the pipe, to call a professional.
They can analyze the combustion process and make the precise adjustments necessary to prevent this problem. Condensation dripping back down the flue causes the flue to corrode and rust prematurely. Flue condensation problems, if left alone, can cause the flue duct to rot and vent hot gases in an area where it could be hazardous to the occupants of the building. Furthermore, there is carbon monoxide present in these gases, and carbon monoxide is very dangerous.
Safety First Flue Condensation Problems
These issues have been observed on all kinds of furnaces, including gas and oil furnaces. Furthermore, if you have this problem or see it on your furnace heating system please consult a professional. If not repaired, eventually, the corrosive condensation dripping down the flue will cause a flue or ventilation failure. Finally, that is a serious hazard to your health.
Additionally, for everyone who occupies the building where this is occurring.
Many HVAC companies have policies always to recommend carbon monoxide detectors be installed. Installed in buildings that have any fossil fuel burners. That includes furnaces, cooking appliances, and other things, including gas logs or water heaters. Furthermore, Safety First!
For information on various flue venting materials and the ratings for those materials see the flue venting materials table. All furnace venting should comply with the Fuel-Gas Code and the Mechanical Code.
Flue Condensation Problems
At my property some people are getting a small water stain on their ceiling from their furnace exhaust condensation. Is there anything I can do to stop this from happening again?
Insulate the pipe
I. Have an exhaust pipe in center of cold air return. Will the cool air from heater cold air return combined with hot air from the hot water heater exhaust cause condensation to drip/stain sheet rock.?.
Will insulating the exhaust pipe resolve this?
Bill, I would say its not a good idea to do something that (actually, potentially dangerous) and is a code violation. It should be re-piped to remove it from the duct.