I’m using a differential pressure sensor with esphome on my furnace filter - before and after the filter to measure the pressure drop.
I decided more recently to go to a MRV8 filter instead of MRV12, in hopes of upping the airflow to my top floors a little bit, and letting my room air purifiers do more of the cleaning work. I have a 5" thick filter, and while the drop across the MRV12 wasn’t too bad, it should be even better with the MRV8.
I can see the new filter is resisting airflow less - before the spike is a MRV12, and after is a MRV8. (The spike is because I switched the ports by accident on the sensor when I was putting things back together)
Nice to see this project come full circle and provide evidence for changes. I still need to fine tune my grafana setup - every time my ERV or heating/cooling calls happen it provides a different reading. So I’d like to someone get a graph that only shows the pressure drop when I’m in a known state (probably just a fan-call state). Then I can use it to monitor how dirty the filter is.
The absolute accuracy for me is less important - I do have a higher quality manometer (150$) and I know with the MRV12 filter I was at about 0.12" WC. The important part is the relative measurement, and the measurement over time where the pressure will slowly increase as the filter gets dirtier. This sensor is only +/- 2% - other sensors can do 0.1% but are incredibly expensive.
As long as your fan is strong enough to be within the sensitivity range then it should be. You could leave one end open to the air, and the other end has a tube going to your duct and it will sense either the negative or positive pressure the fan is making.
Got mine and set it up but having an issue with the accuracy as I understood it. Or maybe I misunderstood it
Online seems like radon fans should be well under 2". .5" being the most common I see.
Using the same drilled hold in the suction pipe, my u tube show .8" WC and my digital manometer show .77-.85". Switching the manometer to kpa shows 0.2kPa.
Hooking up the sensor after zeroing it out and leaving one port open is .43 to .45 kPa.
This would be 1.77".
Am I missing something?
That’s pushing the 2" hard and I don’t want to break it but at the same time, it really shouldn’t be that close so not sure what’s going on.
Typically (in the US at least), you don’t monitor radon continually but rather a fan is installed and draws air from underneath the basement/foundation and exhausts it outside (with no heat exchange, but the air is not directly conditioned, so nothing is lost). Measurements are taken beforehand (which is what will have motivated the install of a fan) and measurements are taken afterwards to show that it’s been reduced below recommended thresholds by the fan. The fan runs 24/7 and typically has a water gauge so you can see it’s working. Pulling this pressure data into HA would be great, particularly if of the gauge is located in a place that isn’t frequented much. In my case I walk by the gauge almost daily, so I haven’t justified doing this yet.
BTW, thanks @gcormier for creating the ESPHome component for the pressure sensor. Just made up a custom PCB and installed it a few hours ago (along with some other sensors I wanted in the area) and getting pretty consistent pressure data. I’ll be curious how much it increases as the filter gets dirty.
No problem! It wasn’t too bad hacking up the code based on other sensors I saw. The esphome devs are top notch on Discord for helping out.
I had a request to add some stuff for a more HVAC oriented board like relays, optoisolated inputs/etc, so I might start that in the winter time. Scope creep is easy for these boards though!
I have an Air things monitor also hooked into HA with a high alert threshold but as was said, radon mitigation is generally sit and forget. The whole radon thing is a grey area but won’t get into that as I don’t really know where I stand with it (I guess I am in the ‘better safe than sorry’ camp). Since I insulated and encapsulated my crawlspace I went ahead and installed some piping and fan at the time. Having your monitor for me is twofold. One - it lets me know the fan is running without going into the crawlspace. Granted, my Iotawatt and ears will tell me this also but more sensors more fun.
The second is a progress monitor. I would have gone to my grave claiming I sealed the heavy mil plastic like a champ but when I turned the fan on and opened an upstairs window the amount of air coming in was easily distinguishable from turning it off. Since getting your monitor I have been going around with a smoke pen trying to find leaks. My hope is that at some point I will see an uptick in the pressure reading.
Edit: I didn’t answer part of your question. The fans are designed for and intended to be ran 24/7. Mine is on a smart plug so at some point I may play around with automating it.
I tried placing a smart switch on my radon fan thinking that I could save some energy by running it less than 24x7. I found that when it was turned off the radon levels would slowly creep up, and when the fan was turned back on it took a long time to get the levels back down. So I think they really do work best when left on 24x7.
I currently have an ESP32 reading a RadonEye sensor to monitor it and have alerts in HA if it raises above 4.0 pCi/L. I have enough confidence now to know that if the fan is running the radon levels are good, so if/when the RadonEye dies I’ll either use one of these differential pressure sensors to monitor it, or perhaps just a plug-in switch with power monitoring.
