Fire Smoke HRV Intake Filtration
I’ve posted before about the fire smoke filtration system I’ve been working with for about 3 years now. It’s based around an 8” AC Infinity (refillable) carbon canister, and a 16x24x5” MERV16 filter. As I write this PM2.5 outside in NW Ontario is 113 ug/m3 due to dense fire smoke. Inside, we’re at 5 ug/m3 while the HRV runs at 75CFM. Video is 1 minute long:
https://youtube.com/shorts/m5MNmqSAIf8?si=Mo_cor0yIPIp4_c1
I hope it proves useful. The system has been in play now for 3 years with temps in winter below -35C. I leave the carbon canister bypassed and use a cheaper filter in winter. Filter life on the carbon canister when used as needed is about 2 years. The MERV16 about 12 months of use.
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Thanks Dennis!
You’re quite welcome Malcolm. We are surrounded by large fires right now and of course the intake filtering is making a huge difference with our IAQ.
The HRV system is getting more sophisticated as I’ve added real time CFM measurements using a few Sensirion pressure sensors. The goal is to actively balance depending on filtration….although surprisingly adding in the MERV 16 and carbon is only dropping air flow on intake by about 5%.
Dennis,
".although surprisingly adding in the MERV 16 and carbon is only dropping air flow on intake by about 5%."
That is surprising.
Wer are lucky here in coastal BC, but my inlaws are in Toronto. The photographs they sent this morning lok like something from a science fiction movie.
Have you thought of how you would set things up on a new build?
Good info. It's amazing how much difference a deep filter makes for airflow.
Malcolm, Michael, the irony here is that a home owner removing the OEM ERV/HRV filter and using a system like mine will likely see more flow (or near identical) from this system as the OEM ones are quite restrictive given their size and thickness. I've attached the pressure/flow numbers from our HRV as I type this. The larger 16 x 24 x 5 filter is rated at .29 w.c drop at 1600 CFM in the Honeywell flavour. AC Infinity rates the 8" refillable carbon canister at 770 CFM, but does not provide pressure numbers. I ended up trying quite a few combinations of smaller filter setups until this one which has very low resistance even with both MERV16 and Carbon in play. You can pick up the MERV 16 from Amazon for about $50, and the refillable 8" carbon works out to about $100 every 2 years or so.
Malcolm, I would likely use the exact same setup on a new build, unless I had a massive equipment room. Having the cabinet outside obviates the need for any insulation, and kind of mirrors the typical industrial rooftop unit where filtration is outside. It's seen three winters now with temps down to -35C and below.
The pressure values in the attached image are across the HRV core, so not a good indicator of relative flow. I can confirm though that at 100CFM, having the entire filtration system out of play only increases intake flow about 5%. Also, if the MERV16/Carbon system is compared to the OEM Venmar internal HRV filter, it flows better, in the 7-10% range and has vastly better filtration.