HI,
I set the thermostat timer for a minimum overnight temperature of 45 degrees, to heat to 70 at 6:30 AM. Effectively, this leaves the furnace turned off overnight. I figure that saves wear on the furnace / fan and saves fuel costs overnight. However, I heard on a radio program that thermostat timers should only have a max differential of about 8 or 10 degrees.
Anybody know what the best settings are?
use 10 degree setbacks for best efficiency and least problems
OK, but why? Does 15 or 20 plus degrees of heat differential mean the furnace gets too hot when running to close the gap, or what?
You wont overheat anything, but there is comfort and air circulation to consider. Yes you will save a bit more but remember you are just heating it back to the temp you need, btus lost btus added. Opinions vary , I set back where it realises a 4 hr drop and for comfort and zone unused areas for less heat. Add insulation for real savings.
Furnace may not be able to get your heat back up in reasonable time and could lead to frozen pipes in hash weather and a bitchy spouse.
Heat is constantly seeking cold to achieve equilibrium. The house is warmer than the outside, so heat is traveling out of the building. You add heat as needed by burning fuel.
Stored heat (sensible heat) is heat that has been absorbed over time. If you allow the air temperature to go too low, the stored heat from the furnishings, fixtures, etc, is also given off. The time to restore it all is making the heater work longer overall than a 10 degree setback.
If you have a heat pump, 8-10 is likely to produce the best savings in most areas. A larger setback can cause more time in supplemental heat mode where it is less efficient.
For resistance heat, every degree of additional setback will save money, but too much could cause damage to pipes and furniture. With the addition of a grand piano my nightly setback has been reduced.
For gas heat, like I have, you still can have some reduction in efficiency, but for the most part the problem is the secondary effects. I would stick to 15 or less.
First what fuel are you using? Do you have an time of day demand meter? Can you and yours stand the temp swings? Longer times off and larger temp differences, mean it takes longer to get back to the set point.
Here in Az the utilities say " more than 5 degrees for more than 8 hours saves more than 10%. However there is an limit to this and doubling the temp and time will not necessary mean double the savings.
Who knows what to believe, but everything I've read says the main reason for NOT setting such wide temps swings is that it'll produce extra wear on a few of the furnace's parts. The instructions that came with my thermostat said
4-7 degrees. I tried 10 in the beginning, but the heat ran so long in the morning that it was stifling in the house. The potted plants were wheezing.One thing I *have* observed is that your sense of warmth is as much related to the objects you touch as it is to the temperature of the air. Some years back, we had an ice storm here which killed power for a week. Once we had heat again, it took almost 3 days for the objects in the house to warm up again. Everything we touched made us feel cold, and this was in a heavily insulated house. Meanwhile, the thermostat cycled normally, saying it was 68 or 70 or whatever we'd set it for.
Anyway....a 25 degree margin doesn't sound right.
Often people will say that this floor is cooler than that floor. Yes, it may feel that way but no, it is the same temperature. It is all about heat transfer.
A wood or ceramic floor will FEEL cooler than a carpeted floor. Why? Because your body is 98 degrees, the floor is about 70 degrees. Heat is always trying to transfer to the cooler spots. When you step on carpet, you are suspended by a network if fibers and plenty of air gaps for insulation. When you step on a wood floor, you have more contact with your skin and more heat is being pulled from your body. Ceramic will pull the heat faster than wood or vinyl.
One more thing since we are discussing heat and comfort. Turning up the thermostat to a higher setting is not going to heat the room any faster. The burner is either on, putting out as much heat as it can, or off, putting out no heat. Cranking up the dial won't make the burner fire any hotter.
I used to be the first in the office where I worked and turned the heat on. Then one of the ladies would com in, turn up the thermostat. Then another would come in and turn it up more, then a third would to the same. I'd go turn it to th e normal setting and they jump all over me because they suddenly felt cold even though the heat was still running the same way.
insulation.
I'm all for equality, but there is something seriously wrong with the way wo men control heating systems. My ex wife *and* he woman I'm seeing now both do the same thing if it's too hot or cold in the car: They turn off the whole system. They only seem to be aware of the fan control, and it's useless trying to explain that other funny knob. "Ya know....it doesn't have to be off or on. You can adjust the temp control somewhere in between...." No reaction. Vacant stare.
Years ago, when I worked in a large office, the women were forever turning the temp up and down, all day long. The boss finally put a locked box over the thermostat, set it for 68, and suggested sweaters. We came close to having an armed uprising, but they got over it.
They turned it DOWN??? A woman actually turned it down? Must have been about 50 and had hot flashes.
One woman was always looking at a little thermometer she had on her desk. If it said 70, she turned up the heat. One day when she went to lunch, we pushed the glass up a little so it read about 3 degrees higher. Problem solved.
For conventionally fueled systems (oil, natural gas) the longer you leave the furnace off, the more you will save. All the "maximum setback" talk is just noise, without any basis in scientific fact.
Courtesy:
Frozen pipes??? When you setback the t/stat by 20 degrees??? Not bloody likley when water freezes at 32 degrees F.
Respectfully, Bob
Art wrote:
I believe it is the opposite for furnace run time and wear, most of your wear is in turning on the furnace, in other words long cycles are better for less wear on components. So the OP wont wear out components faster, just the opposite.
it is an absolute biological fact. women have a temperature range of about
0.2 degrees where they are comfortable. go above that and they turn on the ac. go below that and they turn on the heater. what makes it worse is that not all women have the same baseline temperature, but all only allow for .2 degree swings. get the wrong two women in a room together and blood will be shed.randy
Frozen pipes yes Bob , very bloody likely, when it is - 20f we open our cabinets under the sink and some people even leave a drip. At -20f ive seen mains freeze and pipes in enclosed cabinets freeze because of no air circulation. Even at zero f. precautions must be taken. At - 20 he will wake up to a 45 f house if it doesnt have great insulation, and outside walls will be alot colder.
That happens whenever the room temp drops. There is no threshold.
Every setback saves money and energy, no matter how small or short, even a 0.1 F 10 minute setback.
Nick
Ya....OK...It's 50 at the t-stat.
Who says the temp at the pipe in the basement, you know the one that runs right next to that crappy basement window, isn't 25 degrees?
There have been test showing a diminishing return and a bell on the curve below a certain point. I don't recall where I saw them but you may want to look it up if you doubt it. .
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