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  1. #66
    Join Date
    Jun 2009
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    Albuquerque NM
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    Quote Originally Posted by teddy bear View Post
    Here is an interesting point. The weather data for last year shows that you have high winds abount once per month. I am attaching the data. It show 20-30 mph winds occasionally. This level of wind will reduce the CO2 levels in a home signicantly. This is an opportunity to reset the meter more accurately. Between varible weather and opening the home, ABC calibration should be adequate. Also I found a plastic garbage bag of fresh air around the meter resets the ABC.
    Regards TB
    This is from wunderground.com
    Attachment 336831
    Thanks, more food for thought!

  2. #67
    Join Date
    Jun 2009
    Location
    Albuquerque NM
    Posts
    2,485
    In response to an earlier question, my indoor dew point has been between 35F and 38F every time I've checked it for the last 3 days or so. It doesn't seem to change much.

  3. #68
    Join Date
    Jun 2009
    Location
    Albuquerque NM
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    2,485
    We had a party last week with ~30 people in the house. CO2 shot up to 2500 really fast and tripped the alarm. I couldn't find the instructions to set the alarm level up, so I just shut it off, but it would have been fun to see how high it would get.

  4. #69
    Join Date
    Jun 2009
    Location
    Albuquerque NM
    Posts
    2,485
    Here's a nice explanation of how CO2 sensor Automatic Background Calibration works, from Telaire:
    http://www.telaire.com/refernce/appnotes/abclogic.htm

  5. #70
    Join Date
    Jun 2009
    Location
    Albuquerque NM
    Posts
    2,485

  6. #71
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,337
    Good info. Also You can adjust the setting to low or higher enough to get activation with one person occupancy and calm winds.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  7. #72
    Join Date
    Jun 2007
    Location
    Minneapolis, MN
    Posts
    725
    Or you could open a window on an upper floor...hehehehee

  8. #73
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,067
    Quote Originally Posted by BadgerBoiler MN View Post
    Or you could open a window on an upper floor...hehehehee
    Put an electric actuator on the window controlled by the CO2 sensor.

  9. #74
    Join Date
    Jun 2007
    Location
    Minneapolis, MN
    Posts
    725
    Now your thinkin like a fitter! hehehe=eeee

  10. #75
    Join Date
    Jun 2009
    Location
    Albuquerque NM
    Posts
    2,485
    OK, I've been watching the CO2 levels for a while, and I see a lot of variation. So, I think using DCV (demand controlled ventilation) with the CO2 sensor would be good.

    So, here's what I'd like to have:
    - DCV ventilation to keep the CO2 at some level (800 PPM for example). This should allow in only enough outside air to keep the CO2 below the setpoint.
    - Ventilation limits for low/high outside temperature and high outside dew point.
    - An override with a higher ventilation rate. This would probably require a controlled fan on the duct (or an HRV/ERV).

    My Prestige IAQ has nice features for limiting ventilation on low/high temperature and dew point, but that's it.

    Maybe I need a HRV/ERV with the capability to take a CO2 sensor as input?

  11. #76
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Quote Originally Posted by garya505 View Post
    Maybe I need a HRV/ERV with the capability to take a CO2 sensor as input?

    Ya, that's called commerical building automation or HVAC controls. It's not cheap... even the more basic stuff. However, someone like Jackson system might have a controller that fills that gap and does light commerical and large residential.

  12. #77
    Join Date
    Jun 2009
    Location
    Albuquerque NM
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    2,485
    Quote Originally Posted by motoguy128 View Post
    Ya, that's called commerical building automation or HVAC controls. It's not cheap... even the more basic stuff. However, someone like Jackson system might have a controller that fills that gap and does light commerical and large residential.
    I think you could do something simpler, especially if a HRV/ERV is not needed. Let's say, for example:

    A simple fresh air intake (filtered) for maintaining air quality based on CO2 levels. The intake flow could controlled by variable damper driven by the output from a 2-10V CO2-sensor. It could also be limited by the temperature/dewpoint limits of the Prestige IAQ if desired. This would be automatic and run continuously. The slight positive pressure shouldn't be a problem and might even be desirable.
    Since that would only supply enough fresh air for maintaining IAQ under normal conditions, maybe you could add an additional fresh air intake with a duct fan that could be switched on when needed (for parties, cooking, etc.). This would create significant positive pressure so you would probably need to open a window when you run it, or put in a barometric output damper if you want it to be "automatic".

  13. #78
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,067
    Quote Originally Posted by motoguy128 View Post
    Ya, that's called commerical building automation or HVAC controls. It's not cheap... even the more basic stuff. However, someone like Jackson system might have a controller that fills that gap and does light commerical and large residential.
    Honeywell makes a CO2 sensor that uses contact closure. This could be used to control any ventilation system including ERV/HRV.

    Very reasonably priced.

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