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Controlling Heating/Cooling on a Complex Schedule?
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?"
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.
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.
In the spirit of what people idealize /. to be, I present the URL to an opensource project called DIY Zoning (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:
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.
www.wavefront-av.com