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Thread: The best "away from home for the day" temperature setting

  1. #1
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    The best "away from home for the day" temperature setting

    Hi all,

    I was wondering. Is there any easy (or not so easy) way to determine the best temperature I should set my thermostat to during the day? I'm away from home for many hours during the day so I don't need the heat blasting. However, it seems to me that it might cost me extra by setting it too low during the day (the cost of ramping up to my preferred temperature). Not sure though.

    There are certain variables that I can control and others that I can know.

    I can control the "away from home" temperature, but I can't control the outside temperature (but thankfully, meteorologists can see the future). One fixed value would be my preferred living temperature (60 F).

    Say the average temperature during the day is 23 F and I'm away from home for 12 hours. Is there an algorithm that I could follow to determine the best "away from home" temperature?

    Thanks all,
    Chris


    PS: this is a non-programmable thermostat
    i can only set it before I leave and after I return.

  2. #2
    You will always save money by turning your thermostat down, until you get to a point where cold starts causing damage eg. frozen water pipes bursting. This is because no one's home is a perfect insulator and it will always loose some heat while you're out and the warmer the house is the more heat it will loose. It will take energy to increase the temperature when you get home, but not as much as if you leave it running while you're out. If your house won't suffer cold damage then you can save the most money by turning the heating off while you're out.

    FULL DISCLOSURE: I'm in Australia. I didn't use any heating this winter. It was a warm winter.

  3. #3
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    Quote Originally Posted by Ronald Brak View Post
    FULL DISCLOSURE: I'm in Australia. I didn't use any heating this winter. It was a warm winter.
    Oh, well then, what would you know?

    Quote Originally Posted by m74z00219
    The best "away from home for the day" temperature setting?
    This is an excellent question, m74. I think I've seen it discussed on one of these forums before. And despite his lack of seasonal challenge , I believe Ronald does have the correct solution:

    Quote Originally Posted by Ronald Brak View Post
    You will always save money by turning your thermostat down, until you get to a point where cold starts causing damage...
    Everyone is entitled to his own opinion, but not his own facts.

  4. #4
    Lack of seasonal challenge? :splutter: :splutter: It was 40 degrees celcius in the spring! Hottest spring temperatures in recorded history! I have scouted out storm drains to retreat into in case my air conditioning breaks down!

  5. #5
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    I'm not exactly an expert on home heating myself--it's not that we don't get cold; we had about three consecutive weeks of sub-zero temperatures so far this winter, and Capitol Lake froze most of the way over. I just don't turn the heater on, preferring to curl up under blankets than pay the extra electricity. However, my understanding is that you'll save far more by leaving it on very low during the day than it costs to get it up to your preferred temperature--somewhere in the high sixties or low seventies?
    _____________________________________________
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  6. #6
    However, my understanding is that you'll save far more by leaving it on very low during the day than it costs to get it up to your preferred temperature--somewhere in the high sixties or low seventies?
    If you heat a home at all, then every second it will constantly lose a little bit of that heat energy to the outside. It doesn't matter if the home is heated by one degree or 50, some of that energy will be lost, and the warmer the house the more heat that will be lost. But if you just let the house get cold the heater won't have to continuously replace that lost energy which means that if you come home to a cold house and then warm the place up you use less energy than if you left the heat on, even if it was left on low. As heating is the one thing we can do with pretty much 100% efficiency, turning the heater on high when you come home doesn't waste energy compared to using it on a low setting.

  7. #7
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    Quote Originally Posted by Gillianren View Post
    ...we had about three consecutive weeks of sub-zero temperatures so far this winter...
    Surely you're talking about Celsius? And do you mean three weeks where it never got above 0o C.? It looks like you're in the mid to high 40s (F) now, with lows in the high 30s. I had 18 F. this morning. Kinda cold....
    Everyone is entitled to his own opinion, but not his own facts.

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    Quote Originally Posted by m74z00219 View Post
    However, it seems to me that it might cost me extra by setting it too low during the day (the cost of ramping up to my preferred temperature). Not sure though.
    Nope heat addition and subtraction is linear, and the rate of heat flow from higher to lower temperature is directly proportional to the temperature difference.

    The only trouble you might have with setting the temp too low during the day, is that you might end up losing so much from the thermal reservior which is your house, that the furnace'll have to burn for hours bringing things back up a comfortable temp when you get home. A long burn such as that might be hard on your furnace.

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    Quote Originally Posted by Cougar View Post
    Surely you're talking about Celsius? And do you mean three weeks where it never got above 0o C.? It looks like you're in the mid to high 40s (F) now, with lows in the high 30s. I had 18 F. this morning. Kinda cold....
    Yes, I meant Celsius, though I don't know why. And, yes, we had three weeks where it never got above freezing. Or, if it did, only by a few degrees. It's been warmer than that since then--up into even the 50s once or twice--but we did have three very cold weeks, into the teens (Fahrenheit) or lower at night.
    _____________________________________________
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    "Now everyone was giving her that kind of look UFOlogists get when they suddenly say, 'Hey, if you shade your eyes you can see it is just a flock of geese after all.'"

    "You can't erase icing."

    "I can't believe it doesn't work! I found it on the internet, man!"

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    Quote Originally Posted by Gillianren View Post
    ...but we did have three very cold weeks, into the teens (Fahrenheit) or lower at night.
    I feel your pain. Currently clear and... 11o F. here. For mathematically challenged lurkers, that's 21o below freezing. I realize some places are colder than that, but I wouldn't be anxious to go there.
    Everyone is entitled to his own opinion, but not his own facts.

  11. #11
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    Quote Originally Posted by Cougar View Post
    I feel your pain. Currently clear and... 11o F. here. For mathematically challenged lurkers, that's 21o below freezing. I realize some places are colder than that, but I wouldn't be anxious to go there.
    Cops chased us away from the beach of the lake while we were walking on the trail around it one night, because apparently, people were testing how thick the ice was in a slightly less intelligent way than the guy hucking rocks at it.
    _____________________________________________
    Gillian

    "Now everyone was giving her that kind of look UFOlogists get when they suddenly say, 'Hey, if you shade your eyes you can see it is just a flock of geese after all.'"

    "You can't erase icing."

    "I can't believe it doesn't work! I found it on the internet, man!"

  12. #12
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    Here's my situation, before I give my opinion:

    We have a programmable thermostat. It has 4 time periods, Wake, Away, Return, and Sleep (or some names like that). I can set the start time for each period, and the target temperature which it tries to reach by the time the start time arrives. For both heating and cooling I have a heat pump backed up by auxiliary heat that is only used if needed.

    Here's what I do:
    During the day, I'm almost never away for anything like 12 hours.

    I let the temperature drop more during the night (while sleeping) than I do durin the day. Outside temps are colder at night, and also during the day I might get the advantage of passive solar (on the rare winter days when the sun is actually shining on the house). Also, at night, the period of time when I don't need much heat is longer than during the day.

    Therefore, I think dropping the inside temp during the night is much more important than dropping it in the middle of the day. I generally set a minimum of something in the 55 during the night, and probably 62 when I am away during the day. In between it is set for something I find comfortable but others might find chilly, something like 67. Actually, based on what I've read, I really am not saving much by letting the temp drop in the middle of the day.

    However, if you really are going to be away for a long time, like 12 hours, then that may switch for you.

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    I heard that it you actually don't get any benefit from having a variable temperature setting in your house. In fact you could be incurring more cost if it's set low because of the fuel usage to bring it back up to the wanted temperature. However you do save is you just drop the temperature in general.
    We have our house set at 20c (68f) constantly and the furnace only kicks on to maintain the temperature. We have a high efficiency furnace with a DC motor so we have the blower running all the time to circulate the air. During the day all the curtains in the house are open to capture the solar heat, and at night they're closed to keep it in.

    Our winters are normally cold. The average temperature is around -24c (-11f) and we usually get at least one cold snap where it drops to -35c to -40c (-31f to -40f) that lasts around a week or longer (then add the wind on top of that and you can get wind chill effects of -50c to -60c).

  14. #14
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    Quote Originally Posted by rommel543 View Post
    I heard that it you actually don't get any benefit from having a variable temperature setting in your house...
    Yes; I've heard that too (along with the leaving a flourescent light on). What you never hear are the conditions where this may be true, such as length of time, and inside/outside temperature difference.
    I set mine back during the day and while sleeping. My bill is considerably lower than when I don't.

  15. #15
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    Quote Originally Posted by Ronald Brak
    As heating is the one thing we can do with pretty much 100% efficiency, turning the heater on high when you come home doesn't waste energy compared to using it on a low setting.
    Well, that does depend a little on your heating system. For example, we have a multi-stage geothermal heat pump rather than a furnace. On the lower stages, it's primarily pulling heat from the ground, so the amount of electrical energy used is significantly less than the amount of heat energy brought into the house (coefficient of performance is about 4, depending on the temperature underground). However, while it's quite good at maintaining the temperature using just the first or second stage, to actually bring up the temperature in a reasonable time when it's very cold outside requires it to kick in the third stage, which is basically just an electric resistance heater. Much less efficient. Experimentation has shown that, unless we're leaving for a long time (at least a few days), we actually use significantly less energy just leaving the thermostat at a comfortable level, rather than setting it to vary the temperature up and down. We end up using more electricity if we program it to go down at night, too.

    Of course, we could adjust it to not use the third stage, and then it would save energy to lower the thermostat, but we'd spend a lot of our time in a cold house. If we were going to do that, we might as well just decide to live with the thermostat at a lower setting. So while lowering the thermostat as much as you can at night or when you're away is often a good plan, for at least some kinds of heating systems, it may actually be less efficient.
    Conserve energy. Commute with the Hamiltonian.

  16. #16
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    A programmable thermostat would be a nuisance for wife and I as our schedule is different and subject to last minute changes almost everyday. We like it at least 72 f at night and have a supplemental wood stove which occasionally produces lots of heat, but usually is puny, unless we give it lots of attention. We do turn the thermostat to about 65 f when we expect to be both gone an hour or more. When we return, we turn up the thermostat until it just comes on (our system has no delay) If we turn the thermostat up much more, the heat strips come on which defeats the advantages of a heat pump. Worse we have turn the the thermostat up about 1/2 degree f every two minutes to prevent the thermostat from satisfying, or the the heat strips from coming on. Heat strips may be the reason that some experts recommend not turning down the thermostat.
    What I want is two buttons, marked, I'm cold and I'm hot, and a system that does it's best to fix that for 5 minutes, then defaults back to the thermostat. Neil

  17. #17
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    Quote Originally Posted by neilzero
    Worse we have turn the the thermostat up about 1/2 degree f every two minutes to prevent the thermostat from satisfying, or the the heat strips from coming on.
    You actually have a thermostat that lets you move in half-degree increments? Can you tell me the brand and model? Everywhere I look, I can easily find ones ones with +/-1 F precision, but I can't seem to find one with that will work to +/-0.5 F. I have a digital thermometer that reads to the nearest tenth of a degree, and I've discovered that I can tell the difference (well, not to a tenth, but definitely to a half).
    Conserve energy. Commute with the Hamiltonian.

  18. #18
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    Hmm, it seems that the consensus is to leave the thermostat at a conformable temperature and not fuss over settings. Interesting. Rommel, where in the world are you that your winters are so cold--siberia??

    M74

  19. #19
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    Quote Originally Posted by m74z00219
    Hmm, it seems that the consensus is to leave the thermostat at a conformable temperature and not fuss over settings.
    Well, no. I think the consensus is that it really depends on the details of how you're heating your home. For the system we have, it turns out that it's better to simply pick a comfortable temperature and stick with it. I'm happy that it works out that way, since that's more convenient. But in other cases (generally any scenario with a more conventional furnace and no auxiliary system that comes on to bring the heat up quickly), you'll be better off turning the thermostat down when you're away. Since it can be nontrivial to determine what the best choice might be (and just how much you'd save with the various options), nothing ever beats an empirical test. Try it both ways over several weeks, keep a log book of the meter readings and the outside temperature for each day*, and look at the results. Then you'll know what will work best, and whether it makes enough of a difference for your specific situation to worry about it one way or the other.

    * If you want to be really thorough, you can log other details as well. For example, even with the thermostat set exactly the same, we usually use more energy to heat our home if we're there than if we're out. Why? My guess is that when we're home, we open the door more often, to get the mail, to walk the dog, to get something from the car. A lot of cold air gets in every time that door is opened.
    Conserve energy. Commute with the Hamiltonian.

  20. #20
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    High Grey: My thermostat is a common analog mercury bulb that tilts. It likely is about 1.5 degrees f that turns on the heat strips. After two minutes, I can only guess where it is in the hysteresis, so I guesstimate 1/2 degrees analog increase to avoid turning on the heat strips. Rarely even 1/2 degree turns on the heat strips. Sometimes 1/2 degree (guesstimated) only prevent the thermostat from satisfying for about one more minute. Typically I don't even attempt to read the temperature setting as that requires me to put on my glasses, and doesn't mean much as we sometimes have a ten degree floor to ceiling temperature gradient. Neil

  21. #21
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    Quote Originally Posted by neilzero
    High Grey: My thermostat is a common analog mercury bulb that tilts. It likely is about 1.5 degrees f that turns on the heat strips. After two minutes, I can only guess where it is in the hysteresis, so I guesstimate 1/2 degrees analog increase to avoid turning on the heat strips. Rarely even 1/2 degree turns on the heat strips. Sometimes 1/2 degree (guesstimated) only prevent the thermostat from satisfying for about one more minute. Typically I don't even attempt to read the temperature setting as that requires me to put on my glasses, and doesn't mean much as we sometimes have a ten degree floor to ceiling temperature gradient. Neil
    Yeah, I've actually thought about getting an old analog type, if I just can't find a digital one with the needed precision. If I could even just find one that I can calibrate to closer than a single degree, that would probably suffice.
    Conserve energy. Commute with the Hamiltonian.

  22. #22
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    Quote Originally Posted by m74z00219 View Post
    Hmm, it seems that the consensus is to leave the thermostat at a conformable temperature and not fuss over settings. Interesting. Rommel, where in the world are you that your winters are so cold--siberia??

    M74
    Winnipeg, Manitoba, Canada

  23. #23
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    In all cases, letting it cool down more will use less thermal energy in total. However, there are some other considerations.

    1) How long will it take to heat up? If it takes several hours to heat back up, it might not be worth it even if it is a net energy savings due to the stress on the heater and the relatively short time it would spend at the reduced temperature.

    2) Is the heater more efficient at a low setting than a high one? Any sort of a geothermal setup or heat pump is more efficient than a resistive or gas heater. If you have a multi stage setup, as described by Grey above, you're definitely better off keeping it in a range where the heat pump or geothermal setup can run exclusively. If a resistive or gas heater has to turn on, the efficiency is out the window and it will likely take more energy input to have the same effective energy output (via the vents). Even though the energy required from the vents to heat the house is less, the efficiency will cause the net energy required from the electrical grid or from the gas lines to be higher.

    3) Can anything in the house be damaged by an excessively low temperature? You have to consider thermal stresses if you have the house swinging up and down 30 degrees fahrenheit a day, as well as the potential impact to any pets. If you let it get extremely cold, freezing pipes could become an issue as well, but I'd be surprised if a house could cool down that much in just one day.

    If you have a standard heater though (gas or electric resistive, which are equally efficient at all settings), then it really is quite simple. The energy the heater has to put into the house is exactly the same as the energy the house leaks out to the environment. Conduction and convection (the main heat losses) both scale with the temperature difference between the object and the environment. If the house is at 72F normally, and the exterior temperature is 46F, then by turning the house's temperature down to 59F (halfway between the exterior and normal interior temperature), the energy loss during the day should be cut in half. The savings would be less significant if it were extremely cold out (if it were 7 F outside for example, then you would use 80% as much energy at 59F as at 72F), but they are still there. The energy required to heat the house back up is completely accounted for, as this is looking at the house as a whole system. The additional energy that is needed to heat the house up is the same as the energy lost when the house cooled down, so the energy balance is still valid.

  24. #24
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    Leeches

    Quote Originally Posted by cjl View Post
    In all cases, letting it cool down more will use less thermal energy in total. However, there are some other considerations.

    1) How long will it take to heat up? If it takes several hours to heat back up, it might not be worth it even if it is a net energy savings due to the stress on the heater and the relatively short time it would spend at the reduced temperature.

    2) Is the heater more efficient at a low setting than a high one? Any sort of a geothermal setup or heat pump is more efficient than a resistive or gas heater. If you have a multi stage setup, as described by Grey above, you're definitely better off keeping it in a range where the heat pump or geothermal setup can run exclusively. If a resistive or gas heater has to turn on, the efficiency is out the window and it will likely take more energy input to have the same effective energy output (via the vents). Even though the energy required from the vents to heat the house is less, the efficiency will cause the net energy required from the electrical grid or from the gas lines to be higher.

    3) Can anything in the house be damaged by an excessively low temperature? You have to consider thermal stresses if you have the house swinging up and down 30 degrees fahrenheit a day, as well as the potential impact to any pets. If you let it get extremely cold, freezing pipes could become an issue as well, but I'd be surprised if a house could cool down that much in just one day.

    If you have a standard heater though (gas or electric resistive, which are equally efficient at all settings), then it really is quite simple. The energy the heater has to put into the house is exactly the same as the energy the house leaks out to the environment. Conduction and convection (the main heat losses) both scale with the temperature difference between the object and the environment. If the house is at 72F normally, and the exterior temperature is 46F, then by turning the house's temperature down to 59F (halfway between the exterior and normal interior temperature), the energy loss during the day should be cut in half. The savings would be less significant if it were extremely cold out (if it were 7 F outside for example, then you would use 80% as much energy at 59F as at 72F), but they are still there. The energy required to heat the house back up is completely accounted for, as this is looking at the house as a whole system. The additional energy that is needed to heat the house up is the same as the energy lost when the house cooled down, so the energy balance is still valid.

    Thanks cjl and others that challenged me to think about this a bit more, your words have led me towards a better understanding. I did some of the math and it helped to understand what's going on.

    I looked at just the net power equation to get the gist of it.

    Pnet[t] = epsilon * sigma * A * (T^4 - Ts(t)^4)

    Ts(t) being the surrounding temperature (the temp. outside) as a function of time. And T being the temperature of the outside surface of the house.

    It seems evident now that I can save by lowering the temperature during the day and keeping it at a more comfortable temp while I'm home. Alternatively, I can just keep it at a single temperature (that's lower) and not worry about fussing with it at all. I've opted for a setting of 52 F.

    I've also noticed that (as of late at least) that the day-to-night temperature swings can be pretty significant here in Mississippi (delta 30 F). Also, if one considers my apartment a cube (6 faces), then I'm fortunate that two apartments are adjacent to two of those faces.

    This leads me to an ethical question. If I set my thermostat particularly low (as compared to my neighbors), then the issue of "leeching" arises. That is, when I return home, my apartment will be warmer than it would've been without my neighbors warmer apartments to leech off. Something to think about.


    Thanks again,
    M74

  25. #25
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    Part of that depends on whether or not you have a heat pump. If you do, get a programmable thermostat (they're about $30 for even a two-stage heat pump) and set it to drop to your min temp as you leave in the morning, but also set it to turn back on during the average warmest time of the day (usually around 3 pm). The reason is that a heat pump's efficiency is directly proportional to the exterior air temp. It's most efficient at heating when it's warm outside, and the thermal mass inside your home will retain most of that for two hours until you return home.

    For a gas/oil/electric furnace this isn't the case. Therefore, just leave the heat turned to minimum throughout the day and turn it back on when you return home.

    I'm fortunate in that I live on the third floor of an apartment. I closed off the bedroom I use for storage (about 30% of my exterior wall space), and even though it's been dipping into the teens during the night, and into the 30s or 40s during the day, my downstairs neighbor's heat is sufficient to keep my place warm without my furnace coming on!

    I still have a gas bill, though, as the dummy who designed the apartments put the gas-fired hot water heater in a poorly insulated closet out on the balcony.

  26. #26
    Quote Originally Posted by mugaliens View Post
    Part of that depends on whether or not you have a heat pump. If you do, get a programmable thermostat (they're about $30 for even a two-stage heat pump) and set it to drop to your min temp as you leave in the morning, but also set it to turn back on during the average warmest time of the day (usually around 3 pm). The reason is that a heat pump's efficiency is directly proportional to the exterior air temp. It's most efficient at heating when it's warm outside, and the thermal mass inside your home will retain most of that for two hours until you return home.

    For a gas/oil/electric furnace this isn't the case. Therefore, just leave the heat turned to minimum throughout the day and turn it back on when you return home.

    ...

    I still have a gas bill, though, as the dummy who designed the apartments put the gas-fired hot water heater in a poorly insulated closet out on the balcony.
    Without really knowing your situation you might want to put an insulating blanket around your water heater...but I am sure you have thought of it.

  27. #27
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    Quote Originally Posted by m74z00219 View Post
    Thanks cjl and others that challenged me to think about this a bit more, your words have led me towards a better understanding. I did some of the math and it helped to understand what's going on.

    I looked at just the net power equation to get the gist of it.

    Pnet[t] = epsilon * sigma * A * (T^4 - Ts(t)^4)

    Ts(t) being the surrounding temperature (the temp. outside) as a function of time. And T being the temperature of the outside surface of the house.

    It seems evident now that I can save by lowering the temperature during the day and keeping it at a more comfortable temp while I'm home. Alternatively, I can just keep it at a single temperature (that's lower) and not worry about fussing with it at all. I've opted for a setting of 52 F.

    I've also noticed that (as of late at least) that the day-to-night temperature swings can be pretty significant here in Mississippi (delta 30 F). Also, if one considers my apartment a cube (6 faces), then I'm fortunate that two apartments are adjacent to two of those faces.

    This leads me to an ethical question. If I set my thermostat particularly low (as compared to my neighbors), then the issue of "leeching" arises. That is, when I return home, my apartment will be warmer than it would've been without my neighbors warmer apartments to leech off. Something to think about.


    Thanks again,
    M74
    I notice that your equation contains the term T4 in it. Note that the T4 relationship only holds for radiative heat transfer, which is almost definitely not the primary factor in this case. Conductive and convective heat transfer are proportional to the temperature difference (simply Tin-Tout). The result comes out the same as far as which way is better, but the magnitude of the difference will be changed.

  28. #28
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    Quote Originally Posted by mugaliens
    Part of that depends on whether or not you have a heat pump.
    D'oh, I keep forgetting to mention that I have simple resistive-heating water heater: it's an electric furnace.

    Quote Originally Posted by mugaliens
    I'm fortunate in that I live on the third floor of an apartment. I closed off the bedroom I use for storage (about 30% of my exterior wall space), and even though it's been dipping into the teens during the night, and into the 30s or 40s during the day, my downstairs neighbor's heat is sufficient to keep my place warm without my furnace coming on!
    That is fortunate. Excluding campus, it's unusual for tenements to be that large where I live.

    Quote Originally Posted by mugaliens
    I still have a gas bill, though, as the dummy who designed the apartments put the gas-fired hot water heater in a poorly insulated closet out on the balcony.
    Quote Originally Posted by jaksichj
    Without really knowing your situation you might want to put an insulating blanket around your water heater...but I am sure you have thought of it.
    My old apartment had the same undesirable setup. The water heater was in a drafty addition to the house -- the laundry room. Being that it was the laundry room, it was even more unfortunate as it would've been nice to have the dryer conducting/radiating somewhere closer to the middle of the apartment. Though, it did have a rather thick insulating jacket and I'm sure that helped plenty.

    I second jaksichj's suggestion.

    Quote Originally Posted by cjl
    I notice that your equation contains the term T4 in it. Note that the T4 relationship only holds for radiative heat transfer, which is almost definitely not the primary factor in this case. Conductive and convective heat transfer are proportional to the temperature difference (simply Tin-Tout). The result comes out the same as far as which way is better, but the magnitude of the difference will be changed.
    Are you sure? I used this hyperphysics website as my reference.

    http://hyperphysics.phy-astr.gsu.edu...stefan.html#c2

    What I should've further explained was that I integrated my power equation with respect to time to get the energy lost during the day (roughly the energy produced by the heater) while using a sine function to roughly define the temperature swing throughout a day (Ts[t]).



    M74












    http://hyperphysics.phy-astr.gsu.edu...stefan.html#c2

  29. #29
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    Quote Originally Posted by Grey View Post
    Yeah, I've actually thought about getting an old analog type, if I just can't find a digital one with the needed precision. If I could even just find one that I can calibrate to closer than a single degree, that would probably suffice.
    Since all the home thermostats are "bang-bang" controllers, they work by turning the heat on at a certain amount below the set point and turning off after the temperature at the thermostat is a certain amount above the set point. The closer together the limits, the more often the furnace will cycle on and off. To maintain a constant temperature, the furnace would need some sort of proportional controller.
    Last edited by swampyankee; 2010-Jan-16 at 07:52 PM.

  30. #30
    Join Date
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    4,690
    Quote Originally Posted by swampyankee
    Since all the home thermostats are "bang-bang" controllers, they work by turning the heat on at a certain amount below the set point and turning off after the temperature at the thermostat is a certain amount above the set point.
    Yup. I still want the higher resolution. We've got a separate thermometer that reads to the tenth of a degree, so I've been able to get quite a bit of detail about the system. I've determined that the point at which the system turns off if I set the thermostat to 70 is either 70.2 or 70.3. And I actually find that to be a tiny bit chilly in some parts of the house. If I turn up the thermostat to 71, it works to bring the house up to about 71.2, and that's actually a little warmer than I like it. So it would be nice if I could aim between those two settings. Actually, I wouldn't even need the higher precision if I could at least calibrate the thermostat (well, with the one we've got, I can calibrate it, but still only within single degree increments). It's not that I vary in my heat requirements by that small amount, and that sometimes I want it at 70.0 and other times I want it at 70.5. It's just that I'd like to set it at a spot between where my options are and then leave it there.

    And actually, we've actually got a multizone system. So the inputs from the separate thermostats don't get routed directly to the heating system. They get routed to a separate control panel, that then decides which areas of the house need heat, and can make decisions about when to use the higher stages, based on things like the difference between the temperature set and the actual temperature, and how long it's been working at bringing the heat up. For example, if the temperature difference is small, it starts out using just the first stage, but if it spends more than a set amount of time and hasn't been able to reach that goal, it moves to the second stage even though the temperature difference hasn't changed. So the individual wall thermostats can be simple on-off thermostats, and the zone control device is more sophisticated.

    To be fair, I've probably spent much more time tinkering with the details, but what fun is it to have a complex heating system and not tinker with it.
    Conserve energy. Commute with the Hamiltonian.

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