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  1. #1
    Join Date
    Aug 2005
    Posts
    43
    I use a programmable thermostat in central MD. In terms of recovery, is it easier to heat a house from a set-back temperature, or cool a house from a set-up temperature?

    President Bush's new save energy campaign says to set the set-back temperature back 10-15 degrees in the winter!

    In the summer, I noticed that it took forever to cool a house from a set-up temperature of even 5 degrees.

    --jAmEs

  2. #2
    Join Date
    Mar 2005
    Posts
    997
    OOOHHHH! WHATS the temp out side!!

  3. #3
    Join Date
    Sep 2002
    Location
    I don't know
    Posts
    2,905
    Try different setback temperatures and see what works best for you. It depends on several factors: size and type of equipment, building, insulation, climate, etc. A/Cs are designed to maintain a set temperature, not pull it down daily.

  4. #4
    Join Date
    Mar 2004
    Posts
    1,042
    "Easy" isn't really the right question.

    Except for with a heat pump in heating season, bigger setbacks are more energy efficient. HVAC equipment runs more efficiently by running for long periods to catch up than it does when it runs for short periods to maintain a setting.

    Heat also moves into/out of a structure more slowly when there is less temperature difference between inside and outside, so it actually requires less heating/cooling energy to have a setback period than it does to keep a steady temperature.

    Comfort may be a different story, though. If your equipment is sized perfectly, it will take so long to recover from a setback period that it may not get there before the next setback period... and you may be uncomfortable while waiting for it, too. If that's the case, the energy penalty of not having a setback period is trivial; your savings is in having properly sized equipment that works very hard.

    If your equipment *can* recover quickly after a setback period, it's oversized. In that case, you really should use a larger setback to salvage what efficiency you can out of it. The more oversized it is, the more dramatic the improvement, and the more practical it is to use a large setback.

    In most cases where you use fossil fuel for heating (natural gas, oil, propane) you will probably end up doing well to use a larger setback for heating than for cooling. Most houses with fossil fuel heat can recover far more quickly (in degrees per hour) in heating than they can in air conditioning.

    [Edited by wyounger on 10-18-2005 at 09:30 AM]

  5. #5
    Join Date
    Sep 2004
    Posts
    654
    Kinda wierd to think, then, if a heating or cooling unit is sized exactly right (not too small, just big enough) then a setback stat might not be worth it? Or is better to have a little extra capacity (1/2 ton more on cooling, maybe an extra 10,000 btu for heating) and "make-up" for the minor loss of system efficiency with a setback thermostat?

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