I have a furnace located in my basement in a small enclosed room. I also have a large vent upstairs above this room in my kitchen. I always thought that the furnace takes the air from the kitchen upstairs, heats it up and circulates it back. However, when I was changing the air filter today, my wife asked about the vent located downstairs near the furnace.
It seems to me that the air is bring pulled from 2 locations. First, upstairs by the kitchen and second also directly in the room where the furnace is located (the second location is not ideal. In an enclosed room with hot water heater and sewer pump)
I searched around online and I couldn't find anyone with a furnace design similar to mine that had another intake in the air return. I closed the second intake off by wrapping the vent in a plastic bag to prevent any additional airflow. Once the furnace started again, we noticed a much stronger pull from the first intake upstairs.
Does anyone know why there would be two intakes and will blocking off the second intake in the enclosed room be a problem?
Edit:
The main problem is there is a slight smell that gets circulated from that room. Once I closed it off, the air got quite a bit fresher. My worry is that there was some good reason it was there in the first place.
Best Answer
Actually it is quite common to have multiple air return ducts, with both heating and air conditioning it can save 20-30% by making slight adjustments and changing the flows. I usually suggest dampers on both the supply and return trunk lines for each level for the maximum savings, summer with ac more flow to the upper floor(s) in the winter more flow to the lower floors when heating. This balancing if done well with a air handler appropriately sized can save up to 30% so it may be uncommon in your area but higher end systems do have multiple intakes.