Setting the thermostat lower will save more if it's set back for the same
amount of time. The difference comes into play when you have to set the
temperature up far sooner in order to have the house comfortable at a
certain hour - there's definitely a trade-off there.
If (for instance) you set it back to 50 degrees for 12 hours and then set it
up to 70, you will definitely save more than if you set it to 60 degrees for
12 hours and then set it up to 70. But you'll shiver for a longer time when
you kick the temperature up from 50 degrees than if you had only set it back
to 60 degrees.
The furnace should actually be very slightly more efficient on a long run
than shuttling on and off as it does while maintaining temperature, since
everything in the heating system gets up to temperature, the flue works a
little better when warm, etc. etc. And that's why the current thought is to
size the furnace just barely adequately for the house - to force it to run
longer rather than tripping on a huge furnace for just a few minutes at a
time.
The loss comes in if you set the thermostat to bring the temperature up to
70 degrees at the time that everyone's going to get up or get home. In that
situation the furnace will have to turn on far sooner with a 20 degree
setback than if the setback were only 10 degrees. you won't leave it set
back as long. That will certainly cut the savings, and at some point there
may be less savings from a deeper setback.
Karl
> I had a the same question. I was wondering if anyone knew of a good place
> for figuring out how to set automatic thermostats for better efficacy.
> I've heard that you should not have them drop more than 10 degrees and
> only if you are going to be dropped for more than 8 hours because you
waste
> so much energy bringing the temp back up.
|