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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have side wall concentric vent kit installed to my house.

Customer Question

I have side wall concentric vent kit installed to my house. when the furnace stop running I can feel cold air coming into heat registers. how can I stop this cold air coming back into house from the outside intake vent once the furnace stop running
JA: Did you check the furnace's filters?
Customer: Yes, I changed the filter.
JA: Do you plan on doing the work yourself?
Customer: yes
JA: Anything else we should know to help you best?
Customer: this did not solve my problem, cold air is returning back into house from the furnace when it stop running at the F/A inlet pipe. do u have any other subjects?
Submitted: 8 months ago.
Category: HVAC
Expert:  Regan Land replied 8 months ago.

Good afternoon. The air coming in through the concentric pipe should never go into the ductwork unless there's something majorly wrong with your heat exchangers. A more likely cause of cold air entering the duct system is leaks in the ductwork. I would recommend inspecting the supply and return air ductwork and see if you can spot any holes. If the air is coming out where you can feel it, then the hole should be easy to spot.

Customer: replied 8 months ago.
I get heat, put when it furnace stops that when the cold air come in. I had checked all the ductwork and sealed the holes. when I have taken off the door panel to the furnace I can feel the cold air coming back in after the furnace stop running from the F/A inlet pipe of the furnace. There a panel there just under the F/A pipe that blocks the air from blowing on the burners put the cold air is circulating within the burners box then go into ducts/registers. What do u suggest? should I invest in a damper and where should I place it on the system. What is the heat exchangers?
Expert:  Regan Land replied 8 months ago.

The burner box should be completely separate from the main blower that circulates air through the ductwork and into the house. The heat exchangers are what the flames go through. There should never be air coming from the burner box/heat exchanger into the ductwork.