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Posted by Bob F on January 20, 2008, 9:56 pm
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> Here is a heat pump scenario I just ran into that defies the common
> conceptions about always saving money by setting back the heat at
> night:
>
> Daytime high 60 degrees
> Nighttime low 15 degrees
>
> Thermostat temp inside set at 67 daytime, back to 60 at night.
>
> During the day, the heat pump is relatively OK, going on minimally
> most of the time, due to solar gain through the windows and normal
> household heat generating activities. The heat strips don't seem to
> kick in. We keep it set at 67 until about 11 PM, when the temps
> really start to fall, getting the most efficient use of the unit.
>
> Dropping it down to 60 overnight allows the temp inside to drop to 60
> and the unit goes on and off only a few times, with the heat strips
> helping maintain the 60 set point.
>
> However, cranking the heat back up at dawn puts the unit into trying
> to go full blast, heat the house AND the cooled thermal mass, all at
> the worst possible time, when it is 15 degrees outside. The heat
> strips essentially do all of the heavy lifting before the outside air
> temp can get up to a point that the compressor can work effectively.
>
> If I was to follow the standard rules, our power bill would be high.
> Instead, I inch the thermostat up a couple of degrees, and at the same
> time start a strong fire in the fireplace, and crank on a couple of
> burners on the propane stove to warm the kitchen. Later, about 11 AM,
> or when the outside air is warmer, I'll return the thermostat to the
> 67 degree setting. I guess the alternative is to not get up until
> noon...
>
Or wire it to not use the strip heaters except for defrost. That's how mine was,
unless you turned the "emergency" switch on the thermostat ON.
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