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Distribute Hit in house with Motorized Register?

Discussion in 'Electronic Design' started by Homer, Oct 15, 2007.

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  1. Homer

    Homer Guest

    Hi All,

    I live in a Back Split house (bedrooms upstairs, living room
    downstairs) and have one of those LCD thermostats on main floor. I am
    not really happy with hit distribution in my house. I set the
    temperature in a scheduled order to keep the temperature at nights at
    23 (74) degree but regardless of that our bedrooms upstairs are always
    to hot or too cold (depends on outside temperature). I think the
    problem is cold/hit from outside first hit the main floor (that
    thermostat is) and then bedrooms. Beside this problem I am wondering
    if I can computerize the whole temperature control system. I am
    thinking about someway to software-control temperature of each room.
    So I can bring down bedrooms and bring up living room temperatures
    during the days and backward during nights (or for instance turn off
    hit for guest room if no one is there; no guest). For implementing
    something like this I need two things:
    1- Controllable Air Flow Register (Motorize)
    2- Temperature sensor for each room (this part should be the easy
    part, there are lots of digital single-wire sensor in market that even
    can be chained)

    Anyone knows anything about Motorize Register or any comment on my
    idea? Anyone interested to do it as a team?


  2. D from BC

    D from BC Guest

    Let's say... Open/closed venting. (Not variable position control.)
    How about a bunch of thermostats in parallel to the furnace.
    The furnace runs until the last thermostat open cct's.
    Each thermostat controls a motorized vent.
    If every room comes up to temp, all flaps are closed, there's nothing
    conducting in the parallel circuit and the furnace shuts down..

    No software...

    D from BC
  3. Tim Wescott

    Tim Wescott Guest

    There's a company in Beaverton, Oregon that produces a system that'll do
    this for you.

    But I've been trying to remember the name for the last ten minutes and


    Tim Wescott
    Wescott Design Services

    Do you need to implement control loops in software?
    "Applied Control Theory for Embedded Systems" gives you just what it says.
    See details at
  4. me

    me Guest

    Most central heating systems have "valves" for the duct work ususally
    located near the furnace. These allow you to control the airflow to
    various areas of the house. Close the upstairs a little and open the
    downstairs a little.
  5. Homer

    Homer Guest

    Very smart thinking D. All I need is a motorized vent with thermostat.
    I can even forget about linking them together and downsize the project
    to replace old vents with new motorized ones. I then think of
    something else for shutting down furnace is all vents are shut
    (presure control switch or something like that).

    Now here comes the big question: Is there anything like that in
    market? anybody?

  6. Yep. Search for 'motorized damper'. But these are for installation in
    duct runs and may require chopping holes in walls and floors for a
    retrofit. Motorized registers would seem to make a better option for a
  7. I wonder how such a system would work if only a few rooms call for heat.
    The furnace might not work well with the back pressure and reduced flow.
    In fact, the heat exchanger may reach a high temperature. Most modern
    furnaces have safety sensors to shut down in this case, but hey will
    still treat this condition as a fault and may not even restart until
    properly reset (usually following an inspection).

    High back pressures might also cause 'closed' registers to whistle.

    Paul Hovnanian mailto:p
    Software Engineering is like looking for a black cat in a dark room.
    Systems Engineering is like looking for a black cat in a dark room
    in which there is no cat.
    Knowledge Engineering is like looking for a black cat in a dark room
    in which there is no cat and somebody yells, "I got it!"
  8. ehsjr

    ehsjr Guest

    Don't know what' available in the HVAC world. But
    perhaps you could use the kind of mechanism found
    in some greenhouses to open windows. AIUI they use
    a cylinder that extends a piston when the gas inside
    expands with heat. When the temp goes down, the gas
    contracts and the piston retracts.

  9. Bill Brown

    Bill Brown Guest

    The company you are thinking of is at
    They use inflatable bladders to control each outlet and a RF linked
    thermostat in each room. A central controller received each room temperature
    and setpoint and adjusts the main heat/cool and bladders accordingly. The
    duct bladders are blown backwards through the ducts to the central heater so
    there is almost no installation hassle. Interesting system but I think they
    want about $6000 for a typical system. Ouch!!

  10. Tim Wescott

    Tim Wescott Guest

    That's the one. I know a guy who does software work for them, and
    they've interviewed me to do consulting but nothing came of it.

    Neato idea, and the bladders are a clever way to avoid having to wire
    the house for control (apparently the prototype systems used beach balls).

    But I never looked at the price until now -- that's steep, isn't it?


    Tim Wescott
    Wescott Design Services

    Do you need to implement control loops in software?
    "Applied Control Theory for Embedded Systems" gives you just what it says.
    See details at
  11. Ok, I did a little research on this a while back, and this is what I found.

    First, you use either motorized dampers ($200+ each)or the 'balloon'
    controls ($60 each, but you also need an air compressor and controls for
    around $1000) for each zone you want. You have a separate thermostat
    for each zone that turns on the system and activates the damper for that

    Next, you have a little pressure regulator thingee that is basically a
    weighted flapper that you put right next to the furnace, between the
    output and the return air ducts. This keeps the pressure from being too
    great and burning out your fan. Also, the recirculated air requires
    less conditioning, possibly saving a buck or two.

    Altogether, it can get pretty expensive and complicated.

    Now, in my old two story house, all I did was buy a second thermostat
    for upstairs, and wired it to a two position switch directly above it so
    that I could either switch to the top thermostat at night, or the lower
    thermostat during the day. Funny thing was, I almost always just left
    it on the top one all day!

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