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Controlling Heating/Cooling on a Complex Schedule? 89

Controlio asks: "I've just replaced my furnace, air conditioner, and humidifier last week, in a house that I am rebuilding almost completely from the studs. With the outrageous cost of heating oil, I looked at saving some money by installing a programmable thermostat. However, my work schedule is too complex for most programmable thermostats. The one benefit I have is knowing my schedule a month or two in advance. So, the most practical option seems to have some sort of computer-controlled system that can accept calendar-based setpoints. This would also allow me the opportunity to VNC to the computer from work and change the schedule, in case of last-minute scheduling changes. The ideal solution would be able to control the heat and air conditioner, plus have the ability to do humidity setpoints (though it's not required). Also a system that could control two furnaces would be beneficial, since I plan on installing a heater in my garage this year. Does anyone know any hardware and software combination available to accomplish this?"
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Controlling Heating/Cooling on a Complex Schedule?

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  • by ivan256 ( 17499 ) * on Sunday January 15, 2006 @02:57PM (#14476519)
    As sombody who's doing the same thing to a house,(So far I've cleaned up a fuel oil spill, insulated, replaced all the plumbing, the furnace, the windows (22 new construction windows... Ugh.), the bathrooms, fireplace enclosures, siding, most of the interior trim, and refinished the wood floors), first let me congratulate you and (if you're doing the work yourself) give my condolences for the loss of all your free time from now on.

    The pickings are slim, and short of a multi-thousand dollar (probably more than you paid for your furnace, and certainly more than you'll save in heating costs over the next five years from the programibility) home automation system, you're not going to find anything remotely suitable for what you described. Even then it's not going to be as flexible or open as you're hoping. You can build something yourself, but there are three things you should remember.

    First, you use the most fuel transitioning from your low temperature setting to the high temperature setting. You don't want the low to be too much lower than the high or you'll actually increase consumption, and you don't want to transition too many times per day.

    Second, the more complex you make your program the less change you'll notice in usage. Complexity provides deminishing returns. (At least it should if your house is insulated properly).

    Lastly, and absolutly most important is that you never, ever want your thermostat to fail. As sombody who has just replaced all the plumbing in a two story house, and delt with the concequences of 4' of water in a basement (happened before I bought the house... Got me a good deal.) take my word for it when I say you don't want to do that. Especially if you have oil heat. The bottom rusting out of your oil tank is not fun for anybody. So if you want to make it programable from your computer, that's fine, but make sure it can still turn your heat on and off without your computer, or that you have a secondary manual thermostat that won't let the temperature drop below 50.

    When it comes right down to it though, every ounce of effort and every dollar beyond $100 you spend on this would probably be better spent on insulating. There are some great thermostats off the shelf at home depot like places that have four or five week long programming sets. Get one of those, and on your way out the door every morning, or every monday, pick the program that fits your day.
    • Bah... To be clear, that should have said "four or five week-long programming sets" In other words, multiple programs that it remembers and can easily be switched between...

    • by ivan256 ( 17499 ) * on Sunday January 15, 2006 @03:11PM (#14476628)
      plus have the ability to do humidity setpoints (though it's not required)

      Oh, one last thing. Your relative humidity setting should be a constant function of the outside temperature. Why? Otherwise you risk condensation, and condensation leads to rot and mold. Of course, if your house is insulated properly, a whole house humidifier built into your ducts will never get the humidity up to your requested setting before the furnace shuts off, but that's a whole different problem...
    • Get this [smarthome.com] this [lowendmac.com] and this [perceptiveautomation.com].

      • You're easily pushing $500 (assuming you can get a suitable mac for under $100) just for parts there... How long is it going to take you to recoup that $500 through energy savings over a traditional programable thermostat?

        My prediction? Never. The electrical costs of running the PowerMac 24/7 will be between $11 and $20 a month depending on where you live, and the gas or oil savings will be that much or less.
      • I got my X10 controller for 25 cents, complete with an appliance and lamp module. It works with anything with a serial port, including supposedly a few sun boxes. Why would he need a mac to use one? There's any number of open source X10 apps, and most linux ones (such as heyu, the one that I use), are scriptable. If he wants pretty eye candy software, no doubt he can do that too, and certainly without spending $90 on software. Jesus tapdancing Christ.

        That said, X10 is a pretty crappy home automation system.
    • by BigBlockMopar ( 191202 ) on Monday January 16, 2006 @02:19AM (#14479827) Homepage

      So if you want to make it programable from your computer, that's fine, but make sure it can still turn your heat on and off without your computer, or that you have a secondary manual thermostat that won't let the temperature drop below 50.

      Absolutely agree with you. My little trick, which I do whenever I'm installing a programmable thermostat, is to take the old mechanical thermostat and mount it in the utility room (or wherever else the majority of the plumbing is). Set the old thermostat to its lowest setting and connect it in parallel across the heating leads on the new thermostat (R-W wires only).

      This way, if the new thermostat fails (ie. dead battery), the furnace will kick on before the pipes freeze. Would work doubly well if you've got your computer controlling the heat - even FreeBSD can crash from time to time.

      Another issue - why not consider using small motion detectors to adjust the temperature? If there's no motion, you're either out or asleep, right?

      Insulation is super-important; my house is 600 square feet (tiny WWII veteran's home) in Ottawa, Canada. Each exterior wall was 2x4 originally; when redrywalling a few portions, I've screwed 2x2s onto them to allow the use of 6" thick insulation. With the new windows and a load of fiberglass in the attic, my Trane XV90 rarely kicks on even in the winter; computers and household activities (cooking, etc) keep the house warm enough most of the time.

      Aside: love my Honeywell CT3500. It's a simple 5-2 programmable.

      • You gotta be north-american. Your building-standards are unbelievable. Unbelievable as in low I mean. You upgraded from 4 to 6 inches insulation. Congratulations. Meanwhile, my *grandmothers* house, built before the war, came with 8" insulation, and new housing is not even *allowed* to have less than 10". 12-15" is more common though. (yes, that's a foot, or more of insulation)

        Oh, but this is Norway where it's bone-cold, I hear you think. Only that's not really the best description of the west-coast. The

    • Thanks for the reply. I've spent a lot of time looking at thermostats, and I've found a few that will get me close to where I want to be, but none of them allow remote reprogramming. It's not a deal-breaker, but it's not what I'm looking for.

      In response to mysidia, I'm glad you're on the same page I am. As I posted here [slashdot.org], I can end up spending a great deal of time away from the house - often I go on weekend road-trips or do double-duty and work 14-15 hours a day. That's a lot of wasted heating and coolin
    • First, you use the most fuel transitioning from your low temperature setting to the high temperature setting. You don't want the low to be too much lower than the high or you'll actually increase consumption, and you don't want to transition too many times per day.

      Oft-repeated "wisdom" -- if you let the temperature fall too deeply, it'll cost more to re-heat than you saved in the first place.

      This ignores the plain fact that this is physically impossible.

      • To keep a house warm, you need to add the same a
      • To keep a house warm, you need to add the same amount of heat that escapes.

        To keep the house feeling warm, you need to set the internal temperature higher if the internal surfaces have been allowed to cool down too far. Additionally, your thermostat will keep the heat on until it's warmed up the wall it's mounted on.

        The amount of heat that escapes is, to a first aproximation, proportional to the temperature-differential between indoors and outdoors. (if that is 0, no heat is lost, if it's 60 degrees you wil
        • The proof is in the tests though. Try it and see how much more energy you use when you turn the heat down to 50 during the day instead of 60. It's easiest if you have a gas meter and a few days with the same outdoor temperature.

          I have. At 12 hours, and cold weather, I use 10% less after the house has been at 55 instead of 65 (and yes... measurement is after house warms up).
      • You're absolutely correct that deeper setbacks are (barring a few edge cases) always more energy efficient, so long as the efficiency of the heater doesn't vary. Most don't vary, other than being a bit more efficient when they have longer runtimes (stops and starts are a smidge less efficient). The exception is heat pumps.

        Heat pumps should always be used with a thermostat designed for use with a heat pump. The reason is that heat pumps have an "aux heat" mode that they use when they need to change the te
        • Yeah. Sorta. If you have a heatpump where you can't control that yourself. That is an advantage, because with the setup you mention, one is left essentially guessing how much heat you can demand without going to resistive heating.

          I do have a heat-pump. But it's a bit more controllable, it's got a separate termostat for the resistive heating, I can thus say: Go for 21 degC, but if we'd otherwise drop under 18 -- use the resistive heating.

          Daytime, when I come from work the programming is with a bit of dif

  • by spineboy ( 22918 ) on Sunday January 15, 2006 @02:59PM (#14476534) Journal
    A colleague of mine just rebuilt his house, and his wife wanted heated bathroom tiles, even though we're in L.A. and "cold" weather is like 60F (15 Cel). Anyway they installed a brand new fancy thermostat for both the house and the bathroom. As it turns out, the two systems "fought" each other - the house wanted to cool, and the bathroom floor wanted to heat.

    End result was a $1500 ONE MONTH electricity bill.

    I'll tell you later about the large sized gas stove requiring a commercial grade Halon fire exstinguisher system. HA HA HA.

    • by Anonymous Coward
      I'll tell you later about the large sized gas stove requiring a commercial grade Halon fire exstinguisher system. HA HA HA.

      That I've got to say BS. While many commercial stoves have a fire extinguisher system, halon is used when you have a lot of delicate electronics (isolated server room). I can't see how a gas stove has a lot of delicate electronics. A conventional dry chemical or CO2 fire extinguisher would be fine.

      What's more, halon is toxic and very expensive. Only an idiot would use halon in a kitchen
    • When my parents built the addition onto their house in 1980, electric baseboard heaters were installed (the house is on a slab with no way (at that time) of tying into the central heating duct system (which was set into the slab). The first month they used it (January near Chicago) they got the lowest electric bill they had ever received. The next month was the highest they ever had.

      In the first month, the electricty usage was so great that it had "flipped" the meter so that when the meter was read, it w
    • I gotta agree with the AC here... this would be a really strange application for Halon. Halon's chief advantages are that it leaves no residue and acts very quickly. The chief disadvantage is that it'll rapidly kill anyone who doesn't get out of the room, because it eliminates most of the available oxygen.

      So Halon would work fine for fire suppression, but it'd sorta fail the life-safety aspect of the residential fire code. In residential applications you can expect to have children, disabled, and other folk
  • Yikes!! (Score:1, Insightful)

    by Anonymous Coward
    Excuse me -- you're a mammal. You can survive if you come home, the thermostat hasn't kicked in yet and you need to manually turn the heat up and wear a sweater for ten minutes. I'm glad you at least realize you can tolerate some marginal deviation in humidity.
  • by Camaro ( 13996 ) on Sunday January 15, 2006 @03:02PM (#14476573)
    I know energy is damn expensive these days, but do you really need to adjust it that often? Do you think you'd really save enough to cover the cost of such a complex system by fine-tuning that precicely? Perhaps I'm misinterpreting your needs but if I were in your shoes, I'd go over my schedule and find some common points at which to set temperatures and leave it at that for the period of your known schedule, if that is possible. Just pick the programmable thermostat to fit those needs. I'd go nuts trying to fine tune a system as you're envisioning.

    As for the garage, if you're not going to spend every day in there, I'd suggest a generic theremostat or even a power switch on the furnace. Just turn it on before you want to work in there. If you plan to heat it, you plan to insulate it, so it should heat pretty quickly.

    Maybe it's just me (I'm just a geeky farmer), but I just don't see the point of a complex system.
    • The better the insulation, the greater effect thermal mass will have on your house. I recently had built a new modular house with Energy Star windows, R-30 in the ceiling, R-19 in the walls, and an R-6 Mylar faced insulating blanket on the basement walls extending from the joists to below the frostline, and am heating with a Trane high efficiency heatpump backed up by propane. Because of the good insulation, even if it is in the 20's outside, the temperature only drops a degree an hour or so if I turn back
    • If fuel energy bills are a big factor, why not take a look at energy-efficient heat-pumping solutions as described here [aceee.org]?

      Granted, the installation costs are generally higher, to secure lower running costs, but you could find that the balance works out ok in timescales in which you are interested.

      • The house itself also tends to benefit from constant temperature as well. I found out the hard way that temperature swings can make drywall crack after I heated the house back up after cutting the heat back to 50 when I went away for several days. Frequent temperature variations also start to work loose fasteners such as nails and screws as well, and can eventually result in squeaky floors, cracked grout, and nail pops in drywall as well.

        My guess is that this happened beacuse of changes in humidity rather t
  • Way too much work (Score:3, Insightful)

    by linuxwrangler ( 582055 ) on Sunday January 15, 2006 @03:05PM (#14476588)
    Wow this sounds like a lot of work. I think I'll stick to my current "system":

    1. Too chilly? Turn on the heater for a few minutes.

    2. Too hot? Open the windows/turn on a fan.

    But you're right - energy is getting expensive. I just broke $100 for gas/electricity last month.

    • energy is getting expensive. I just broke $100 for gas/electricity last month.

      Hahahaha... Guess you're not in the snowbelt. :)

    • I agree that turning up the thermostat when you get home is not a problem, especially if you have a sufficiently sized furnace as opposed to a wimpy heat pump. The problem that I have is that more often than not I forget to turn the thermostat back down when I leave in the morning. This can be especially bad if my wife decided that I did not turn up enough in the first place.
  • DIY Zoning (Score:4, Informative)

    by Midnight Warrior ( 32619 ) on Sunday January 15, 2006 @03:16PM (#14476660) Homepage

    In the spirit of what people idealize /. to be, I present the URL to an opensource project called DIY Zoning [sourceforge.net] (that is, Do-It-Yourself for those who live in an apartment). It is a very well designed website with links to best practices and pointers to basic parts and the sourceforge-based software. From the site:

    A collection of bits and pieces of knowledge to explain how to put together mostly off-the-shelf inexpensive equipment and make a temperature zoning system out of it, and a software product that allows you to control the hardware.
    • Re:DIY Zoning (Score:2, Informative)

      by nbSouthPaw ( 935530 )
      This is one of the biggest suggestions I could make. I recently used products from : retrozone.com They have the only product that I have found that will easily retrofit an old house with zone technology. I spent about 500 dollars on parts and pieces. In the last year I have already made up for what I have spent. My winter bill is the same as last years which is pretty good considering prices have almost doubled in that time. If you goto: http://www.resconsys.com/products/stats/ [resconsys.com] They have various z
  • FreeBSD (Score:1, Troll)

    This would also allow me the opportunity to VNC to the computer from work and change the schedule, in case of last-minute scheduling changes.

    Well, it's clear that you've alredy found a solution, and now you're just searching for a problem to solve with it.

    However, I really think you should step back and thought about the problem you're trying to solve. If you weren't so hung up on the technology, you'd realize that a thermostat running the X Window System would probably work just as well.

    Yes, it's clear to
  • Why not just manually change things manually? Any disconfort tempature-wise is just something you have to accept for saving $.

    Think how much a system like this is going to cost and how much in man-hours its going to set up. Then factor in the time and effort to fine-tune it, adjust it on an on going basis. Is it really worth it to save on the heating bills?
    • Though I usualy hate these types of "do you really need this" replies, this is a pretty fair question.

      I live in Michigan. I am not yet living in this house (still very much under construction and awaiting an electrical inspection) and I keep the house at 45 degrees when not being worked on... the lowest allowed by my thermostat. This is partly due to a few uninsulated walls and an underinsulated hole in my ceiling... read this post [slashdot.org] for details. Anyways, I got my gas bill for last month... for 9 or 10 wor
      • Its an uninsulated house (and a hole in the ceiling), I'm sure that the heater is going to work more than normal.

        Think how much you make per hour. Think how much time you are going to spend setting up and maintaining the system. Think how much you will save in gas. Is it worth it?

        Would it just be worth it to "suffer" with a cold house for a while because you want to save some $, rather than to go for a complex system?
  • If I were doing something like this I'd be looking at micro PLC's. Besides giving you the temperature control capability you are looking for they offer the potential to do a lot of of other home automation jobs.

  • by clark625 ( 308380 ) <clark625@yaho[ ]om ['o.c' in gap]> on Sunday January 15, 2006 @03:31PM (#14476751) Homepage
    If you don't mind writing a script or two, you're not looking at something that's impossible on a lighter budget. The X10 standard is actually pretty sucky, but I put it in my old house and it worked out okay. Raised the value of the house roughy 10X what I put into it, too. Anyway, check out smarthome.com [smarthome.com], specifically this product [smarthome.com].

    Disclaimer: I haven't used this specific product. I have used just about every other X10 product, though, and the smarthome site does a pretty good job of explaining how to set things up. I used to use a wireless transmitter on my Linux box and some scripts put together called "firecracker" to communicate. Simple cron jobs did the rest. If I recall, I also had a device that transmitted/received from a serial port to the power lines directly, but I don't know if they still sell those or not.

    If you really want to control your heat and A/C this way, I STRONGLY suggest taking lots of temperature samples of where things are at and ensuring you aren't wasting energy because of poor control systems. One mistake in code and your bills will go wild.
    • I set up an X-10 based home automation system using an old computer (programmed by me in AppleScript running on a PowerMac 7100, if you must know) that has a "home" and "away" mode -- for instance, any time I'm away, the vacation timer automatically runs, whereas when I'm home, the driveway IR sensors will activate the plug-in chimes. (My friend has a similar system which she refers to as "turning on" or "turning off" the house.) The gist is, in both our cases, that when we leave or arrive, we hit a butto
  • If you're replacing the furnace and tearing the house apart as much as you say, why not switch to electric or radiant heating? The difference between the cost of electricity and heating oil will lower your heating costs more than a computer-controlled thermostate ever would.
    • Oil heat is usedd predominately in the North East states. In New England oil has been by far the most economical choice for most of the past 15 years. In Massachusetts it is a real drawback when you try and resell a house if it is electric heat.

      I locked in my oil price at $2.04/gallon this year. I will burn on average about 1000 gallons, but this is due to windows needing to be replaced and other issues. Electric would be much more.

      To reduce my consumption I did just purchase a cheap ($45) 7 day programable
      • And another benefit of radiant heating is that you can easily create zones. My current house has steam heat and it has only one thermostat to regulate the whole house. The thermostat is located in the living room where the windows are old and let a draft in. The boiler keeps firing to keep the drafty living room warm but the upper floors turn into a sauna (one night it went below zero and my room was no joke 95 degrees). The way I combat it is to cover up all the windows with plastic and turn down the therm
    • Re:heating oil? (Score:5, Informative)

      by Phreakiture ( 547094 ) on Monday January 16, 2006 @12:39AM (#14479501) Homepage

      If you're replacing the furnace and tearing the house apart as much as you say, why not switch to electric or radiant heating? The difference between the cost of electricity and heating oil will lower your heating costs more than a computer-controlled thermostate ever would.

      Absolutely, 100% totally, completely incorrect.

      Electricity costs more per BTU than oil, period. This is because electricity is, quite frequently, made from oil, gas and coal, usually at a 30-35% efficiency, never at better than 50% efficiency. Then there are the logistics issues of delivering the ultimate perishable good, invariably losing some of it on the way. All of these contribute to its cost. You WILL pay more per BTU for electricity than for any fuel.

      A good, high-quality oil or gas furnace will start at 90% efficient and work up from there.

      As for suggesting radiant heat as an alternative to oil, that is the same logical fallacy as suggesting a car instead of a Subaru. Radiant heat uses electricity, oil, gas, coal, or whatever else fuels your boiler.

  • I recently replaced the thermostat in my house with a programmable. The thermostat that I purhcased (the Hunter Fan model 44760) http://www.hunterfan.com/prodSum.php?pid=20&pType= thermo&sType=4 [hunterfan.com] had an ethernet port on the back of it. IIRC, it mentioned somethings about future development, and I haven't tried it, but you might check it out. A little hacking and you might come up with something.
  • Insulation? (Score:3, Interesting)

    by PastaAnta ( 513349 ) on Sunday January 15, 2006 @04:16PM (#14477019)
    Now, I am just curious.

    How much insulation did you use for your roof, walls and floors?

    Here in Denmark the houses are normally rather well insulated and made with brick walls or concrete walls. Therefore the time-constant is often so high, that changing the temperature hour by hour normally doesnt make any sense at all. In our house we have floor heating with tubes in the concrete floor and it takes several hours to change the temperature. Its good for keeping the feet warm in a cold winters day :-)
    • Materials.... (Score:1, Insightful)

      by Anonymous Coward
      If the original poster is from America, most likely his house is wood from the sill up; wood is still relatively cheap in the US. Concrete construction in single family homes is much more common in Europe than America, and plumbing/heating systems in Europe reflect that difference.

      Insulation technology for wooden houses has improved immensely in the last 20 years, and it's probably a better investment of time and money to figure out how best to button up the house, and get a nice programmable thermostat th
    • Here in Denmark the houses are normally rather well insulated and made with brick walls or concrete walls.

      Is that because of the cold? My understanding is stone, or rock, will hold heat far longer then wood or aluminum siding.

      You don't mention what type of insulation, nor the amount, that is used in your Denmark houses.

      Our house was built ~3.5 years ago in Columbus, OH, US. I believe it's built close to these:

      Ceilings: R-49
      Walls: R-21
      Floors: R-30
      Basement Walls: R-13

      We have stone on the front, but siding on
    • This is a North American house, in Michigan. It is a 1950s brick house, and all of the existing insulation is blown-in. I have torn out the living room exterior wall, the kitchen exterior wall, and a load-bearing center wall that has left a hole in my ceiling. Also, the basement is uninsulated at this point.

      We put up some R19 in the ceiling hole for the time being, and the open exterior walls will get insulated as soon as I can pass an electrical inspection (re-did electrical completely - there was some
  • Here I am, having recently moved to a 3 bed former council house built in the 1930s, with a gas-fired central heating system from the 1970s, so it's not exactly efficient. This is a colder than usual British winter, and gas prices are rising sharply. The envelope from nPower flopped through the letterbox the other day and it was opened with trepidation.

    ... and it was eighty quid for three months. Oh, was that it? Hardly worth me buying anything to try to reduce the usage.

  • ...in the agriculture (poultry houses for instance) and greenhouse industry. You'll need to research there for it I don't recall brand names off the top of my head right this second, but should be easy enough to find examples of. They have systems that are both automatic programmable there at the dedicated computer and remote controlled over the internet for monitoring and adjusting, heating,cooling, humidity, etc. Warning: it's spendy stuff, but will do what you want. I also really doubt any of the softwar
  • Everything you need to manage your schedule is a d/a board and crontab on linux/Unix.
    • How about this instead:

      0) get better insulation.

      1) get a cluster of Intel PCs (especially those that use 250W or more of power under load). A slashdotter can always find a way to use more computers ;).

      2) run lm_sensors on the PCs - this is how you get your temperature readings.

      3) Depending on the time, date, derived ambient temperature and other customizable info, decide whether to run CPU intensive jobs on your computers.

      Voila - temperature control :).


      There are many useful CPU intensive jobs you can
  • X10, and a couple of other companies, make X10-type protocol thermostats. X10's appears to be just a setback controller, but it's only about $20. A company called RCS seems to make a full-fledged X10-controlled thermostat for around $250.

    Yeah, they were obnoxious with their popup stuff, but their products work well enough, and there's other people who make boxes that work over the protocol. Fire up a linux box with a Firecracker on it, and use at/cron/whatever ot control your thermostat. Or go all the w
  • This might get ugly, especially if you don't have that much experience with hardware/software programming, but you could make something yourself. Dick around with the thermostat for a while until you figure out how you can control it with a relay. Then look in designing and programming some software to control it (add on or parallel port). This is quickly sounding like a geek project, but if you have the time and interest it could be fun and cost efficient. You might also want to look into any off the s
    • by Stevyn ( 691306 )
      Sorry, I meant X10, not X11. And one more thing to add, what about adding more heating zones so you only heat the parts of the house you need too. Older homes with one heating zone can waste a lot of money whereas if you only need a few rooms warm and toasty and the others at around 60, you could save some more money.

    • Dick around with the thermostat for a while until you figure out how you can control it with a relay. Then look in designing and programming some software to control it (add on or parallel port).

      Hack the existing thermostat? Relays shorting buttons. My Honeywell CT3500 has up and down arrows for a temporary (2 hour) override of the program.

      To replace the thermostat, would be very easy to control the furnace and AC by computer. Most systems use between 2 and 5 wires on a 24VAC control system.

      Colors of th

  • I work in the business of doing this type of control in large buildings. Typical home thermostats are grossly inadequate for larger buildings. The type of products we manufacture allow any kind of custom programming you can dream up and although the "language" is something like BASIC, I have seen products that can execute Python scripts (see original story comment).

    Normally this stuff isn't used in residential buildings because of the cost and complexity, but that didn't stop me. :)

    Drop me an email at gre
    • Predictive things work great in a commercial building, when what you need to consider is heating and cooling but you are not very concerned about hot water production. But I am willing to bet that the home in question uses oil for both heat and hot water and it is probably a tankless system. The system is going to be running everyday anyways.

      Now I suppose you could do some pretty neat things to automate a heat and hot water system, like have it learn when you usually do dishes/ laundry/take a shower and a
  • An overly complex system may be a negative factor for resale. A buyer may not want that level of control and complexity.

    I put in a programmable thermostat about 8 yrs ago (in conjnction with a whole new heat pump system). It allows for 4 different settings for each day of the week. But because of spouse/kids in and out all the time, I pretty much just keep it at one setting. Heat to 67-68 in the winter, cool to 74-73 in the summer. It is good for reminding me to change the filter, though.

    I also have a wor

  • A very simple solution with some safety built in would be this: Use two thermostats. Set one for the 'home' temerature and one for the 'away/sleep' temperature. Use a relay with SPDT contacts, controlled by the computer/timer/whatever, to select which thermostat is on-line.

    This will not allow for remote re-setting of setpoints, but it will allow you to select which of two preset setpoints is active at any given time. Additionally, the failure mode will be to have one of the two thermostats on-line, ca

  • OK, first a disclaimer. I do this for a living and I am recommending the company that my company is a dealer for. I am not unbiased. I'm telling you what I would do if you were to come to me and request that we do the work.

    http://www.kmc-controls.com/ [kmc-controls.com]

    These guys make a many different sized PLCs with a very easy to use programming language and excellent control features.

    For a house with a radiant floor system, a forced air system, a complex schedule, and internet access. You could probably get away

    • You want pnumatic or electrical air dampers with that? :p Residental zone systems are always a pain because of the cost and labor involved. But once they are established, the client trained in it's operation and how to make changes to the system when and if they want to, accolades abound. Zoned systems for large homes are wonderful for they can be adjusted on the fly for occupancy or activities. Zoned systems can be customizable to a degree, but that's it.. There is a size limit at the small residential ho
  • I've been thinking of the same thing myself, except I've decided against it (I'll go into why later).

    While I've had OK results with X-10 equipment (they were a good company until they started their popunder/spam/camera obsession. rather than updating their products for modern times, they went on an annoying advertising spree. The end result is that Smarthome's Insteon is going to kick X-10's ass in its original market.), I would go with something more robust/flexible than X-10 now. Smarthome (www.smarhom
  • > However, my work schedule is too complex for most programmable thermostats


    Why restrict yourself to the ones that don't work? Why not buy one of the other ones for which your schedule is NOT too comples???

  • THe perfect keyboard for you would be the IBM Model M! Durable, terrific feel and......really compact...
  • The HAI Omni security systems have really good integration with the HAI Omnistat programable thermostats. The Omni security systems have a very simple macro language for setting up commands based on security, timed, user input or security sensors and the result can be a change in thermostat settings. For example we have ours programmed to setback the thermostat to 60 after 10pm (11pm on weekends). After 5am if the motion sensor in the bathroom triggers (indicating I stumbled into the bathroom for a show
  • Rather than micromanage the thermostat schedule, a low-maintenance alternative would be motion or occupancy sensors in some key locations.

    If you're home, you'll trigger them and get heat, if you're not then have it default to 55F or whatever is good for your area.

    But as others have said, insulation and weatherproofing may be a better investment than a geeky control system. When the furnace kicks on it's not just heating you at that moment, it's got to burn a lot of fuel make up for being off for N hours.

  • I've looked at controlling the heat with programmable thermostats and so on, but it's either a) too much work, or b) too expensive.

    Enter phidgets (www.phidgets.com). I've never used them, but they look like just the thing. I discovered them on an carputer forum (mp3car.com) a few weeks ago.

    Cheap, USB, linux-compatible. What more could you wish for?

    Temperature sensors and everything.

    I'm going to leave the manual thermostat at 45-50 degrees, and add a relay (phidgets have relay controls!) to the thermostat
  • I use a HAI Omnistat RC-80 computer controllable thermostat (available here [smarthome.com] for about $160, or cheaper on ebay), a serial cable (made from CAT 5 cable), and some software I wrote (available here [sourceforge.net]) for computer control.

    The thermostat operates on it's own (no risk of freezing pipes if the software chokes), but you can reprogram it through the serial port, including changing mode (heat/cool/off), temperature set point (seperate for heat and cool), the schedule for automatic setback for weekdays/saturday/sunda

    • This looks perfect - exactly what I need. And the on/off hours tally allows me to do some real nice things like billing estimates and schedule optimization.

      The only bummer is I can't see your software on sourceforge - it says no file packages found. But looking at the manual for the thermostat, it doesn't look too complicated to conjure something up.

  • 1) Presumably you've looked into 'home automation' and suchlike? I've never used it, but I understand there is a home automation standard known as X10. A quick search for "X10 HVAC" reveals there's [smarthome.com] a [xcicorp.com] few [simplyautomate.co.uk] about [smarthomeusa.com].

    2) You talk about VNCing in from work. A system that needs a PC on 24/7 probably won't lead to a net energy saving, since your computer is probably consuming more than 100W any time it's on. If you would have your computer on anyway, consider turning it off and getting a $10/month shell account somewh
  • An even better way to reduce heating/cooling costs is to ensure that your renovations make your house as energy efficient as possible - look at insulation, air flow, passive solar considerations for shade in summer and exposure in winter. The more you do now to design a home that will maintain even temperatures on it's own, the less you need to intervene with heaters and air-con.

  • Does anyone have a pointer to a web site or book that helps you calculate the average R-value of a house? Seems like it would be not tooo hard to do if you had the right rules. For instance, a table (set of tables really) or web site should be able to correlate effective house R-Value to indoor temperature change rate, average indoor temperature, average outdoor temperature. This is quite a few variables to measure at once, but basic measurements and formulas should be enough. With a few assumptions and
    • Does anyone have a pointer to a web site or book that helps you calculate the average R-value of a house?

      I took a class on this in Construction Management. I takes a good half hour to do a house or small business building, and you have to know the R-Values of windows, insulation (materials and thickness), etc. Check the Library, because the textbooks are pricey, and cover a lot more than you want for just this task.
  • There is a great bit of kit I am using in a conversion to do just this - called a webbrick. have a look at http://www.o2m8.com/ [o2m8.com] this thing has built in schedules, web configurable or you could use cron with python to control from your computer. It will fit in a standard consumer unit (din mountable) an is a doddle to set up initially, as well as being flexible if you want to have a more complex configuration.

"The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts." -- Bertrand Russell