mike wrote:
On 1/25/2013 7:19 AM, Jim Elbrecht wrote:
On Thu, 24 Jan 2013 16:27:08 -0800, 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.

You're at least the SECOND. While I am indeed measuring the fan time,
they invented math to calculate a good approximation of the burner time.
For the limited temperature range over which relative measurements
are relevant, the time to heat the heat exchanger to
operating temp is relatively constant. And the fan turnoff delay is a timer.
My cumulative (adjusted) readings correspond well with the gas meter readings.

It don't vary enough to affect the conclusions.

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.

You're certainly correct that the sun adds more heat than the computer.
And I can see that too.
According to my measurements, my computer is currently supplying about 10% of my
space heating energy. Don't matter if it's day or night. And you see
the same relative effect from the air-conditioner run time in summer.

That simple measurement influenced me to set the computer's
sleep timer much shorter so it's running less. Heating with gas
is cheaper than heating with computer.

FWIW, I have another PDA program that uses the IR port to "watch"
the led on the electric meter and plot electrical consumption.
Kinda neat to watch the water heater or the fridge or the furnace fan
go on and off and calculate the energy consumption. I can get a fairly
accurate measurement of what a hot shower or washing a load of clothes
costs me.

If you don't get too nit-picky, you can learn a LOT from relatively
simple measurements with little investment.

Jim

My old oil burner took 5-6 minutes before the fan came on. Temps at
register were high. The fan turn on was at the lowest possible setting.

Greg