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Heating, Air Conditioning, Fridge, HVAC/outside vent to cold air return ductwork


My wife and I recently purchased an 11 year old home. The furnace and central air are Tappan, the model of the furnace is FG6Rc 060c-12a. When the weather gets below zero the furnace seems to turn off and right back on a quite a bit. I was looking things over and I noticed that one of the vents to the outside of the home is a flexible insulated pipe that connects directly to the cold air return ductwork. What purpose does this serve? It seems to me that although this would add fresh air to the house, it has to take more energy to heat very cold air from outside. The furnace does have the air intake and exhaust pipes like other high efficiency furnaces, I just have never seen an outside vent attached to a cold air return. If this is just for fresh air, would it cause any harm to seal it off during very cold stretches to reduce how hard the furnace has to work to heat the air? Thank you for your help!!

Unless there is some reason to exhaust air from the house, there is no real reason to have it.  It may have been put there by the previous owners you wanted fresh air added in.  Blocking it off should not hurt anything.  Building codes do differ from place to place, so it might be there due to some kind of building code.


Heating, Air Conditioning, Fridge, HVAC

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Craig HVAC Expert


I have been in the HVAC field for the past 18 years. I can help with most HVAC questions. I work on commerical buildings for the most part, and have yet to find anything I could not troubleshoot and repair, when repairable. I work on small 1 ton units to a 2500 ton chiller. Troubleshoot air flow, elect, and control problems. I attend regular classes to keep up with the latest and greatest.


I work on commerical sites, hospitals, gov't buildings. I can troubleshoot just about anything in the HVAC business.

5 years trade school, VFD training classes, Liebert factory training, some York and Trane factory training.

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