What's Wrong With This Picture? Dryer Vent vs. Forced Air Furnace Vent
Answer: Improper venting configuration.
A perfect reason to have a home inspection! This find by one of our home inspectors may have saved a life.
The upper pipe the inspector is pointing to is the clothes dryer vent pipe. The lower pipe is the forced air furnace exhaust vent. While conducting an inspection of the dryer venting components, the inspector noticed heat from the operating furnace (exhaust?) coming through the dryer. At this particular moment, the forced air furnace was running and appeared to be functioning normally. The gas flame within the furance was bright blue and vibrant. Turning the clothes dryer on changed everything, immediately revealing a very depressed, lazy, and yellow flame at the furnace, indicating improper and possibly dangerous combustion conditions.The pressure and movement of forced air from the dryer venting was suppressing the atmospheric condition of the chimney and not allowing the furnace to evacuate it's exhaust gases. Some of those gases, including dangerous CO, at this point in time, are being pushed back into the home.
The inspector also noticed the furnace began short cycling about every 3 minutes. Short cycling is a term used when the appliance comes on and then shuts down repeatedly. Furnace sensors are being given mixed messages and attempting to respond. Turning off the dryer allowed the flame and furnace function to return to normal. Turning the dryer back on, the short cycling resumed. How frequently do you suppose the homeowner was drying clothes when the furnace was operating? Probably a lot during the home heating season!
The Issue Revealed.
Forcing dangerous exhaust gases into the living area is only one of a whole host of potential issues with this configuration. There are more, including lint buildup and fire potential. Understand this, a dryer vent should never be vented into the same chimney as a gas appliance. Dryer vents are required to have their own venting system, separate and distinct from other appliances.
Thank you Timothy Shelton of our Maryland area inspection team for this submission. Very good catch!
