Air quality sensor for balanced HVAC system?

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CrazyM

110 posts

Master Geek
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#303982 26-Mar-2023 07:22

Hi,

I've currently got a Cleanaire balanced HVAC system which I love that is constantly intaking fresh outside air and exhausting our stale internal air. Its of the manual control variety; set the speed on a dial and it runs at that speed all day every day. I wish it was a bit smarter in that it would vary the intake and exhaust fan speeds separately but that is a separate issue.... I currently have the HVAC plugged into a TP-Link Tapo smart plug which lets me remotely turn the system on and off, set timers, monitor consumption etc... It fits my level of home automation where I dont have much desire for regular monitoring and intervention/micromanaging, but I also dont have any issue in spending time getting a system set up initially if that means it can then run unattended for a decent period.

My issue is that my neighbour has a smoky wood fire so when the weather conditions are wrong my system sucks up the outside smoke and evenly distributes it through my house. Distinctly sub-optimal. My current plan is when I smell smoke I just turn off the system from the Tapo app and then set a timer to turn it on again in a few hours so I dont forget. I can also schedule the HVAC to be off in the early morning and evening when his fire is starting up and smokiest. Not ideal, but okay.

My proposed improvement would be to put some kind of smoke/air quality sensor in my HVAC air intake. So when it smells smoke (or air quality goes down for some reason) it can send a signal to turn off my HVAC at the smart plug. Does anyone know if such a thing exists?

Cheers

Handle9

11401 posts

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#3054720 26-Mar-2023 07:52

CO2 and VOC sensors are readily available, as are duct smoke detectors, and widely used on HVAC applications. They are expensive though and you’ll need some way to monitor the sensor. They are generally 0-10v sensors fed into a control system or clean contacts in the in the case of the duct smoke sensors.

There’s also cheap IOT devices around, I have no idea of their quality.

k1w1k1d

1527 posts

Uber Geek

#3054722 26-Mar-2023 08:48

Would a charcoal inlet filter help to stop the smoke smell?

CrazyM

110 posts

Master Geek
Inactive user

#3054726 26-Mar-2023 09:03

I already have a charcoal inlet filter and it does a decent job but its still obviously smoky air coming in.

I dont really want to go down the full custom route, a similar device to this (with air quality monitoring) would be perfect https://www.tp-link.com/au/smart-home/smart-sensor/tapo-t310/

tweake

2391 posts

Uber Geek

#3054839 26-Mar-2023 10:58

what filter are you running on it? i suspect you have a low grade filter which is letting smoke through. fitting a larger higher grade filter would be the best thing.

the other option is smoke alarm sensor which can then shut the unit off. some systems come with them as standard. however i suspect low amounts of smoke won't trip it so you may still get some smell through.

voc or co2 sensors could be an option but run the risk of many other things setting it off.

edit: the charcoal filter will probably render the voc or co2 sensors useless as it will capture a lot of the things that will trigger the sensors. you would need the sensors before the filter.

tweake

2391 posts

Uber Geek

#3054844 26-Mar-2023 11:04

CrazyM:

Hi,

I've currently got a Cleanaire balanced HVAC system which I love that is constantly intaking fresh outside air and exhausting our stale internal air. Its of the manual control variety; set the speed on a dial and it runs at that speed all day every day. I wish it was a bit smarter in that it would vary the intake and exhaust fan speeds separately but that is a separate issue....

my mem i think the later ones are EC fans and are controlled separately. early ones you need to use dampers to tune the flows. imho they should not have a user accessible fan speed. once they are tuned for the house it should be left alone.

timmmay

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#3054877 26-Mar-2023 11:38

You could get the new Ikea air quality sensor which with some effort integrates with Home Assistant, and use that to turn the power to the system on and off. Home Assistant has a fairly steep learning curve though, but once you have your devices integrated you can do just about anything you like. They're only US$10 on sale, usually US$15.

If anyone works out how to get those sensors to NZ fairly cheaply I'd get a couple.

CrazyM

110 posts

Master Geek
Inactive user

#3054893 26-Mar-2023 13:56

I have a new Cleanaire with EC fans, but they are both controlled off the same pot and ramp together. The reason why I would like them adjustable separately is because I have additional restriction on the intake fan (G4 and carbon filters) and my preference would be to run the house at a slight positive pressure. Currently I just have to close down the exhaust vents

That ikea sensor is heading in the right direction. A little too homebrew for me currently but it looks like a step in the right direction. Maybe in a few months they will be a Wi-Fi enabled one on the market

Sharesies

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tweake

2391 posts

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#3054898 26-Mar-2023 14:27

CrazyM: I have a new Cleanaire with EC fans, but they are both controlled off the same pot and ramp together. The reason why I would like them adjustable separately is because I have additional restriction on the intake fan (G4 and carbon filters) and my preference would be to run the house at a slight positive pressure. Currently I just have to close down the exhaust vents

have a chat to avon/cleanaire, balanced ventilation should have separate pots on the unit for adjusting the fans flow rate. there is always restriction in the system which you need to adjust for. its stupid to have to resort to dampeners because the manufacture left out the controls. also they may have some ideas on the smoke issue as they make a wide range of air handlers with all sorts of controls.

G4 is a course filter, i suggest going to a finer filter. (edit: try a hepa filter)

SomeoneSomewhere

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#3054962 26-Mar-2023 18:44

Depending on where the pots are and how smart the system is vs just a pot connected to an EC fan, adding a second pot may be trivial. I've literally got a Fantech 0-10V 10K pot in a light-switch form factor on my desk.

If you can get any smart home equipment that receives a 0-10V or 4-20mA external signal, then connecting a standard industrial air quality sensor will be trivial.