Conversation

HRV Mark II. I made several changes to the design based on what I saw from the first trial run:

1. I made an entirely new ingress tube. The holes I had drilled in the bottom of the cans were too small for the limited air pressure produced by the fan, so instead I cut ~1.5" suqare holes of of the bottoms with a Dremel. The airflow is noticeably better.

2. I replaced the 120mm ingress fan with a 60mm fan. The internal diameter of the intake is only ~50mm, and I was using a canning funnel as a reducer, but I noticed this caused a lot of blowback. Even though the 60mm fan moves less air, there's no blowback, so I think it'll probably be equivalent or better. I was also able to put it in a nicer looking housing.

3. I believe I had an imperfect seal at the end of the ingress tube, causing some egress air to mix in with it as it exited. I stuffed a bunch of polyfil in the gap, which seems to have made a big improvement.

Before, when I stuck my CO₂ meter into the ingress tube, it was registering ~800ppm (the meter reads outside air as 490ppm). Now it reads just above 500. I think the extra few ppm are due to my egress and intake fan being relatively close to one another so there's some inevitable mixing. Close enough though.

In terms of heat exchange, It's about 80F inside, 49 outside, and I'm reading the incoming air at about 79F, so that part of it is definitely working as intended. I can also feel that the air coming out the other end is quite cool.

What remains to be seen is what impact, if any, this will have on the ambient CO₂ level in the room.

#hrv #heatrecovery #ventilation #co2 #airquality #physics #diy #upcycling