I'm going to guess that the anticipator
is set for too short intervals.
Of course, it could be other things
causing the problems too.
As most new furnaces turn the blower on
immediately when the
thermostat calls for heat, cold air will
blow until the heat exchanger
gets hot .... a bad idea, from a comfort
standpoint, IMO. Usually
there is a current rating on the gas
valve or control system, which
is the setting of the anticipator. You
can go a bit "longer" or "shorter"
than that setting, however, not too far.
Too far towards the shorter,
will probably cause problems as you
describe. I usually start at the
rated setting, and adjust from there a
bit, as required. Of course, as
some have said, a programmable unit is
much better. The one I have,
basically, does the anticipation
function in the software (firmware), but
I have seen it turn on and then off,
prematurely, especially when there
is aa outdoor temperature swing

dave wrote:
I don't know the brand, but its one of those brown dial thermostats.
I've played with various settings on the heat anticipator with no
results. The t-stat does control the heat and temperature most of the
day. In the evening hours, temperature drops all the way to low 60s.
Sorry J, but if it weren't for my limited understanding of the system I
wouldn't need to ask for help.