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

[tedkidd]

Panasonic has bath fans that ramp up and down based upon motion sensing. Put one in my GF's house, set continuous at 30, jumps to 80 or 100 when it senses.

My ERV has all kinds of settings, and a 15 minute high button in the bathroom. (She's not thrilled when I see the master control showing "high fan" and I shout "are you pooping?"
She keeps a copy of Dale Carnegie on my bed-table, and I can almost hear her thinking "read the book a-hole!") :-)

I suspect what you want is out there.

[Chuck]

Teddy Bear,

Do you have a link to the product from Ultra Air that you talked about that controls ventilation by CO2 levels?

[teddy bear]

Teddy Bear,

Do you have a link to the product from Ultra Air that you talked about that controls ventilation by CO2 levels?

This is a custum control without support currently. Will become a fully supported control in a few months. From what I am seeing, If the space never gets below 600 ppm CO2, the control will read 450 when it is really 600. You set the control to activate at 600, this provides fresh air when occupied.
In addition, when you have active ventilation, the space may will be at 600 when you leave the space. Thus the space will go lower and readjust the sensors reading.
Also the ABC number and time is programable. This means you can determine the time and ppm. Currently we are using 450 and 2 weeks.
I have access to a limited number of custom DEH 3000 controllers with CO2 control of fresh air ventilation. I have some operating for upto 18 months of operation. Refinements a being made as we speak. I am using them on different types of ventilation systems like ERV, make-up, and exhaust systems.
Regards TB

[garya505]

This is a custum control without support currently. Will become a fully supported control in a few months. From what I am seeing, If the space never gets below 600 ppm CO2, the control will read 450 when it is really 600. You set the control to activate at 600, this provides fresh air when occupied.
In addition, when you have active ventilation, the space may will be at 600 when you leave the space. Thus the space will go lower and readjust the sensors reading.
Also the ABC number and time is programable. This means you can determine the time and ppm. Currently we are using 450 and 2 weeks.
I have access to a limited number of custom DEH 3000 controllers with CO2 control of fresh air ventilation. I have some operating for upto 18 months of operation. Refinements a being made as we speak. I am using them on different types of ventilation systems like ERV, make-up, and exhaust systems.
Regards TB

I think this will be a popular product. With the cost of CO2 sensors dropping, emphasis on energy conservation, and increased awareness of IAQ, having an integrated product should be a good thing.

Of course, it appears that you can combine a CO2 sensor with any type of ventilator and maybe accomplish "almost" the same thing.

Oh, and if one of the high-end thermostat manufacturers would add CO2 sensor input to one of their thermostats, well that would be excellent too.

[teddy bear]

I think this will be a popular product. With the cost of CO2 sensors dropping, emphasis on energy conservation, and increased awareness of IAQ, having an integrated product should be a good thing.

Of course, it appears that you can combine a CO2 sensor with any type of ventilator and maybe accomplish "almost" the same thing.

Oh, and if one of the high-end thermostat manufacturers would add CO2 sensor input to one of their thermostats, well that would be excellent too.

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
History for Albuquerque NM.pdf

[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
History for Albuquerque NM.pdf

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.

[garya505]

Honeywell makes a CO2 sensor that uses contact closure. This could be used to control any ventilation system including ERV/HRV.

Very reasonably priced.

That's what I was thinking. With an HRV/ERV you could use the CO2 sensor relay to cycle the unit. Since you are recovering most of the heat, the ventilation temperature limits wouldn't really be needed. You still might want to use the ventilation dew point limit though, depending on the local climate. I can see why most people wouldn't bother with the extra cost of a CO2 sensor. If you are getting 70-80% energy recovery, it doesn't matter as much if you are over-ventilating, and the ROI on the CO2 sensor is long.

With a simple supply-side fresh air intake, you could use the CO2 sensor's proportional 10V voltage output to control an actuator on a damper to let in just the right amount of air. Since there is no heat recovery, you would also probably want to use both the ventilation temperature limits and the dew point limit.

[teddy bear]

That's what I was thinking. With an HRV/ERV you could use the CO2 sensor relay to cycle the unit. Since you are recovering most of the heat, the ventilation temperature limits wouldn't really be needed. You still might want to use the ventilation dew point limit though, depending on the local climate. I can see why most people wouldn't bother with the extra cost of a CO2 sensor. If you are getting 70-80% energy recovery, it doesn't matter as much if you are over-ventilating, and the ROI on the CO2 sensor is long.

With a simple supply-side fresh air intake, you could use the CO2 sensor's proportional 10V voltage output to control an actuator on a damper to let in just the right amount of air. Since there is no heat recovery, you would also probably want to use both the ventilation temperature limits and the dew point limit.

I like the CO2 control to activate fresh air ventilation when the home is occupied and the natural infiltration rate is low. I do not like the idea of not providing a small amount of fresh air ventilation when it needed. 70-80 cfm of fresh air during cold or damp weather and the home is occupied is very small energy cost. My experience is that during cold windy weather and home occupancy, little or no fresh air is needed. So small energy cost. During damp, calm weather, the full 80 cfm will be required. The cost of dehumidification is minor. Indoor air quality is more important than saving a couple bucks. Get a good ventilating dehumidifier connect to a CO2 controller set low enough to activate the ventilating when the space is occupied by one. This typically +650 PPM CO2. My experience is very little running during winter occupancy and ventilation required during calm weather whenever occupied. Lets keep this going!
Regards TB