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Simplest question ever

  1. Dec 14, 2007 #1
    So, this is hardly even an engineering question, but here it goes anyway.

    I'm off from college; my parents are at work and my brother is at school. I'm the only one in a 4 person house with central air, and I'm cold. So I turn up the heat. But I'm the only one home, and I'm just in my bedroom. I don't need the living room, bathrooms and other bedrooms heated, just my bedroom. So I'm wasting a ton of heat just so that one relatively small room is a few degrees warmer.

    So has anyone ever engineered a way to heat only specific rooms with central air? It seems like it'd be very easy to just make switches for each air duct to control whether they stayed open or were shut off. This way, in situations like mine, I wouldn't have to burn enough fuel to raise the whole houses temperature so that I can be warmer, I'd only have to burn a fraction of that. It could also be useful for houses where certain rooms are perpetually colder or warmer than others.

    It seems, from here, that it wouldn't be hard to automate the system, have a thermostat in each room, and have air ducts that let an adjustable amount of air in, so that when the heater is running, everyone can control exactly how warm their room should be.

    Does this seem unreasonable to anyone? I feel like the technology to do this is at least half a century old, yet I'm not sure it's ever been tried. With prices for fossil fuel so high lately, it could also save people a lot of money, and make whoever started selling it some money as well.
     
    Last edited: Dec 14, 2007
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  3. Dec 14, 2007 #2

    mgb_phys

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    Reduce energy usage - that sounds like commie/european talk!
    The system in my office in California was even worse, it cooled the air with an airconditioner first - then heated it to the temperature set on the thermostat!

    With air it would be failry easy to completely shut off unused rooms but it is harder to control the heat in them by partly opening the vent - the pressure differences in the system are low so the flow doesn't necessarily go where you expect.

    There is a better systme involving the mass flow of special a high specific heat capacity liquid around the house in a pipe, to heat the room it is deflected into large surface area metalic structures.
    I can't say too much I'm hoping to patent it.
     
    Last edited: Dec 14, 2007
  4. Dec 14, 2007 #3
    Sounds like US talk :P
     
  5. Dec 14, 2007 #4

    stewartcs

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    Why not just use a space heater for the room you're in? They are generally less efficient than the central units, but if the area you are heating is small it may be more economic.
     
  6. Dec 14, 2007 #5

    FredGarvin

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    The system is zoned heating. It allows the control of any number of predetermined zones in a house. It solves exactly the problem you are describing. Of course, that means your entire distribution system has to be designed for that kind of control.

    http://www.uniteddesign.com/idea_workshop1_97.html
     
  7. Dec 14, 2007 #6

    stewartcs

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    I wonder how much (if even possible) it would cost to change your current design to this?
     
  8. Dec 14, 2007 #7

    russ_watters

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    I'm considering doing zoning in my house, though my ductwork is not well laid out for it. If a system designed with zoning in mind, the zoning would only add a couple of thousand dollars to the system (perhaps 5-10% of the cost). All the major manufacturers sell this type of equipment, but not generally retail. Here's some retail equipment: http://www.smarthome.com/307107c.html

    In the meantime, you could always just close the dampers in the supply registers in the rooms that don't need heat. That's what I do now.

    By the way - in commercial buildings, this is called a Variable Air Volume (VAV) system. And it isn't the simplest question ever. There are some major complexities that these types of systems can create and poorly designed/installed VAV systems are a big problem in a huge fraction of commercial buildings. I'm currently involved in a lawsuit (on the side of the plaintiff) where the original design engineer of a school created a building pressurization problem that was so bad the boiler exhaust was sucked though the basement and into the building instead of going up the stack.
     
    Last edited: Dec 14, 2007
  9. Dec 15, 2007 #8

    FredGarvin

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    I often wondered that myself because my house desperately needs something like this. My home (built in the '60s) has darned near separate weather systems in it. The temperature variations are tremendous, even with playing with dampers and louvers.

    I would think that an enterprising company could design a sort of valve manifold that attached to the outlet of a furnace that provided the required valving. That doesn't address the code requirements for run size, etc... I would think a retro fit would be pricey.
     
  10. Dec 15, 2007 #9

    Astronuc

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    We doubled the size of our house, but the central heat could only handle the first floor and we decided not to upgrade with a larger system. Instead, each room upstairs have electric heat at the base boards. The upstairs is very well insulated, so we don't need to use the electric heat very much. At night the heat downstairs is turned down, and each upstair room is heated individually according to the occupant.

    During the summer, we use removable window A/C units, one for each bedroom, and one for the downstairs area. We use open windows as much as possible. Eventually, it might be worthwhile to replace the entire central heat system with a new central cooling/heating system.
     
  11. Dec 16, 2007 #10

    brewnog

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    I just have thermostatic valves on all my radiators...
     
  12. Dec 16, 2007 #11

    FredGarvin

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    I miss having rads. This is a moot point if you have them. The only advantage of having forced air is the possibility to have central air.
     
  13. Mar 1, 2008 #12
    Yeah, it can be done. Go to the basement and your furnace. You should be able to locate the ducts carrying the air and sometimes there are levers or stoppers that you can flick from one side to the other so that heat only goes to a particular area (not room, but area)...then follow the duct and there shoyld be another lever.

    In the meantime use a space heater.
     
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