"Pete C." wrote in message
ster.com...

Ed Huntress wrote:

"Pete C." wrote in message
ster.com...

Ignoramus10802 wrote:

On 2009-10-29, Pete C. wrote:

Ignoramus10802 wrote:

On 2009-10-29, Stormin Mormon
wrote:
Please forgive me while I troll for a moment.....

Is it energy saving to turn the thermostat down, when
leaving the house? I mean, the furnace has to run to catch
up when I get home. I have a way of looking at the matter.
I'll explain my point of view after the argument is
underway.


Imagine for a minute that you have to leave house for a month.

Would it be energy efficient to turn thermostat down? Of course, as
less heat will be produced for a whole month, with only a few
minutes
to catch up.

The same applies to only one day.

i

It's far more complicated than that. Factors such as insulation /
heat
loss, type of heating, multi-stage heating, electric backup heat on
heat
pumps, etc. all come into play in determining the away duration and
temp
reduction where savings begin, and in some cases (typically high
efficiency homes) it can require a multi day absence to see any
savings.

This is patently untrue.

i

No, it isn't. It was documented on a well monitored high efficiency
model home where the backup heat strips on the high efficiency heat
pump
were kicking in in order to provide a reasonable temp recovery time
since the heat pump itself did not have the capacity. The electricity
used during the temp recovery was more than would have been used on
temp
maintenance due to the switch to lower efficiency backup (100% vs.
300%+).

But that only tells you that a lower-efficiency temperature-recovery
system
is...lower in efficiency. If you have that particular pair of heating
systems, you have one situation. If you have a more-typical single
heating
system, you have quite another.

That isn't a "pair of heating systems", nearly all heat pumps include
backup heat strips for times when the heat pump is not able to produce
enough heat such as very cold weather / high demand.

Again, you're talking about 8% of homes, at most.



In the case you've described, you aren't dealing just with the
thermodynamics of the situation. You're also adding the complexity of
multiple heat sources that operate under different circumstances.

That complexity exists everywhere and that was my point - you have to do
the actual analysis of the home in question to get the correct answer -
you can't rely on blanket statements / myths.

No, it doesn't exist everywhere. It only exists where you have multiple
heating systems operating at very different levels of efficiency -- 8% of
homes, at most.


An additional complication is occupancy, since for folks who are retired
or work from home, or a stay at home spouse, you loose half or more of
your theoretical savings period with the occupants not being away during
the day.