Pros and cons of HRV vs Fresh Air Ventilation in a dry heating/cooling climate.

[garya505]

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!

[garya505]

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.

[garya505]

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.

[garya505]

Here's a nice explanation of how CO2 sensor Automatic Background Calibration works, from Telaire:
http://www.telaire.com/refernce/appnotes/abclogic.htm

[garya505]

And another one from AirTest:
https://www.airtest.com/support/refe...tocalpaper.pdf

[teddy bear]

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

[BadgerBoiler MN]

Or you could open a window on an upper floor...hehehehee

[Chuck]

Or you could open a window on an upper floor...hehehehee

Put an electric actuator on the window controlled by the CO2 sensor.

[BadgerBoiler MN]

Now your thinkin like a fitter! hehehe=eeee

[garya505]

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?

[motoguy128]

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.

[garya505]

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".

[Chuck]

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.