6" fresh air intake with a manual damper running from outdoors to the main return duct under the house. This draws air whenever the blower in the forced air furnace is running. I don't see any place on the supply side main allowing this extra drawn in air to return to the outside world.
The question is: If say, there were 10cfm coming into the system from outdoors when the furnace blower comes on, then where does this extra 10cfm of air go when it leaves the supply side registers? It has to leave the house somehow.
Out through leaks in the construction of the house? The bathroom vent fans even if they aren't on? The fake fireplace flue?
Is there supposed to be a duct on the supply main under the house that takes an equal amount of air back outdoors? Am I underestimating just how leaky houses are?
If the house were really tight, how can this fresh air intake even suck any air in?
Lotta questions. Apologies, but if you can explain this and bring me some science I would appreciate it. Maybe link me to something that explains it.
The question is: If say, there were 10cfm coming into the system from outdoors when the furnace blower comes on, then where does this extra 10cfm of air go when it leaves the supply side registers? It has to leave the house somehow.
Out through leaks in the construction of the house? The bathroom vent fans even if they aren't on? The fake fireplace flue?
Is there supposed to be a duct on the supply main under the house that takes an equal amount of air back outdoors? Am I underestimating just how leaky houses are?
If the house were really tight, how can this fresh air intake even suck any air in?
Lotta questions. Apologies, but if you can explain this and bring me some science I would appreciate it. Maybe link me to something that explains it.
source https://hvac-talk.com/vbb/showthread.php?2224193-CFM-in-should-equal-CFM-out-right&goto=newpost
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