This is my first winter in a house with an oil-heated, forced air system. I noticed my wall vents were pushing out warm air, but the floor cold air return vents were pushing out cool air. I followed all the ducts and found a booster fan pulling cold air from the outside, and pumping it into the ducts. I covered the outside hole with a piece of rigid insulation, and that has stopped the fan from turning on, and the cool air from coming up my vents. (they do suck cool air into the furnace) Did the previous owners make a mistake, or am I missing something?
Why is the booster fan pulling cold air from outside
hvacintake-fan
Related Topic
- Use a power gable fan and ceiling louver vents to pull cool air into the house
- HVAC system that pulls-in cold air from outside
- Basement – High humidity in an unused, air-conditioned, finished basement; dehumidifier
- Two ducts Blowing hot air, 4 ducts blowing cold air
- Home Ac unit is not turning on
- HVAC: hot attic, system off, heat leaking in from supply vents
- Does the furnace suck air from outside
- Why don’t the inline booster fans operate as expected
Best Answer
It would appear to be a poorly tuned fresh air vent (aka a "Make-up Air vent")
Blocking it completely is not a good choice.
Tuning it correctly is a good choice.
The intake should not be bringing in more air than the furnace blows out (far less, in general)
A page from 11 years ago...
http://www.nchh.org/Portals/0/Contents/Read_This_Before_You_Ventilate.pdf