I don't know where to begin on this one...
First off, it's a coleman Evcon furnace, located external to the house in Wisconsin(yeah... I wonder about the previous owners...)
Anyways, the ductwork runs through the walls to the attic. The ducts do not seem very large for the size house. It almost seems as if the house itself had a heater in the attic at one point in time.
There are 2 cold air returns (one located in the back living space, and one not connected in the attic. There is a moderate amount of airflow through the living room vent (it's 3 feet from the furnace). The attic return does not have much airflow to it.
I replaced the furnace filter a few days ago (the last one was really dirty). I checked the ductwork, and everything is connected, nothing is crushed (that I can see). The ductwork is insulated, and there doesn't seem to be any major air leaks.
The heat vent in the living room kicks out a lot of air (I would have to say just a bit more than the average furnace would). The rest of the house cannot even come close to the air volume coming out of the living room duct.
When I went outside and opened the filter cap, I noticed a very large quantity of air being sucked in. This may have had something to do with the air filter restricting the air flow (point of least resistance....), but I could be wrong. I didn't think of running inside and feeling if more volume was coming though the vents.
I don't know what exactly is causing this, or how to fix it.
Obviously a plugged air return could be the problem, but most of the ducts are in hard to reach places. Are there any easy ways to test this?
The blower motor could be failing, but shouldn't the pressure be constant, instead of most air flow in 1 vent and very little in the rest I guess that situation could be true since the vent with the most airflow is the closest one to the heater.
The main ductwork appears to have to go through studs to get to the attic. Could the previous people cut corners to get from point A to point B, causing a massive restriction in airflow?
Or, should I just call the pro's? The unit needs an inspection anyway, but the heat portion does work...
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