On Thu, 24 Jan 2013 16:27:08 -0800, mike wrote:
-snip-

I did the experiment. Put a flapper on a microswitch and stuck it on a
register.
PDA graphs the percentage on-time for each cycle. And keeps a running
average.

http://imageshack.us/photo/my-images...mondisplay.jpg


Let me be the first to observe that you aren't measuring how long the
burner is running- but how long the *fan* is running. They will be
similar-- but variable.

Most interesting thing I learned is that the house has a very long time
constant.
I turned the thermostat from 65F back to 60F and went to bed. Was in
the low 30's outside. 7 hours later,
the furnace still hadn't come back on. When I added up the run-minutes
to get the house back up to 65F and compared to what it would have used
keeping the place at 65F, the difference was in the noise level.

Another interesting observation is that when I wake up and turn on the
computer, there's an observable drop in furnace output. Kinda interesting
to watch for the first week. After that, not so much.



While the computers will add a bit to your heat output-- I'll bet the
sun helps more. To test my theory- work nights for a week and see
what happens.

Jim