On Thu, 29 Oct 2009 18:51:43 -0700 (PDT), DD_BobK
wrote:


So the laws of themodynamics are different from system to system?

Heat its lost to the environment based on the difference in
temperature between the heated space & the unheated space. As the
temperature of the heated space falls, the heat loss also fails. When
the temperature of the heated space falls to that of the unheated
space, heat loss stops.

I believe you are confusing the "time" it takes to recover with "huge
amounts of energy are required to re-heat everything".

If you were correct in your thinking (& oyu are not) the whole concept
of temperature setback would not work (& it does).

cheers
Bob

I think part of this is because we tend to think of the heat needed to
heat something from the outside temp to what we want inside. But
what the furnace does most of the time is just replace heat that is
lost to the outside. And still it runs a lot.

So it runs even more when it has gotten colder than normal inside,
because it was on setback. But it has run not at all perhaps or much
much less the entire time people were out and the thermostat was set
back.


Looked at another way, the furnace is usually just raising the temp
one or two degrees, from the temp at which it turns on, 67^? to where
it turns off, 69^?, and still it runs a lot when we are home