I'm wondering if there is a major air leak in the return air.
Perhaps the furnace is sucking in only cold cellar air.

It's one of those situations where someone has to come out and
look, and look over the entire situation.

I'm in the Rochester area. What part of the city are you in?

--

Christopher A. Young
You can't shout down a troll.
You have to starve them.
..

wrote in message
ups.com...
Lately I had been noticing that the temperature of the "heated"
air
coming out of my gas furnace was barely above room temperature,
75
degrees by my infrared thermometer. Filter is nearly new, flame
is a
perfect blue.

Turns out that the problem was I'd opened up the registers to a
couple
of rooms, and the "redumbdant" register in the living room.
After I
closed the registers again, the temperature of the heated air
shot up
to 110+ degrees at the furnace.

Now, my gut is telling me that this furnace is undersized for
the house
if I can't have airflow to more than one register in the living
room,
one in the breezeway and one in the main hallway without the
register
temperatures dropping to barely-above-ambient. Any expert
opinions on
this? House is 1300sq ft, furnace is 64,000 BTU, location is
Rochester,
NY. Former owners were snowbirds and the furnace never had to
do more
than keep the house at 50 over the winter.