During my inspection of forced air furnace I inspected the ducting and the supply plenum. I noticed immediately the supply air plenum (See Photo Ventilation 3)was not insulated on the interior or exterior of the plenum and the 90° take off (See Photo Ventilation 4) going to the 1st floor was not insulated either. I ran the furnace and ensured that it ran, the flame looked good and a CO test showed me that the heat exchanger was intact. however when I walked through the house I noticed that the registers were unusually noisy and the house did not seem to get warm enough. A cursory look at the return grille showed nothing unusual however I noticed that only 3 ducts came out of the plenum and they were (1) 8" diameter and (2) 7" inch diameter ducts . That is not enough duct area to allow for proper airflow. Air is moving too fast across the heat exchanger and it does not stay in contact with the exchanger long enough to heat the air sufficiently to warm the home.
This means that the heating system is:
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Loosing heat through the uninsulated portions of the air distribution system (ducting)
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That improper air flow ( too high of a velocity of air) is making the system both ineffective and therefore inefficient because the heater stays on much longer than necessary to heat the home.
A peek in the attic where ducting is distributed will probably reveal ineffective seals at joint where air loss will occur judging from the work observed at the FAU.
30 seconds to note some points that may be of interest to a new home owner to have issues resolved prior to purchase or reduce price in order to have issues resolved at new owners expense.
