On Friday night, after the wife turned off the TV and went to bed, I had just stoked up the stove and left the blower off waiting for the wood to char before setting the air. Anyway, I started hearing a strange fan noise... traced it to my HRV. I decided to turn it off since it was very cold out anyway and figured I'd check it out the next day.
With it off all night, it couldn't run the de-icing cycles so I had to blow some heat on it to melt the ice. Once the ice was gone, it would not make the same noise so figure ice buildup was the likely culprit. While I was at it, figured I may as well rip it apart, dry it out well, clean it, and inspect it. Found a lower seal compromised and the squirrel cage fans had a lot of dirt buildup. Replaced the seal, cleaned her all up and was impressed with how much quieter it was. Funny how noise sneaks up on you and you don't notice. Anyway, impressed with the results, I turned my attention to my stove's central heat blower.
It is a variable speed 650 CFM, 8 inch centrifugal in-line fan. I built a housing for it down in the crawlspace where it draws in cool air off the painted concrete floor through a prefilter. It then goes through a flexible noise reduction coupler into the housing which has a labyrinth muffler and a 16x25x1 Filtrete high particulate filter before going up through the floor into the bottom of the stove. Ja, I know... I'm anal about sound reduction.
After seeing the failed seal on the HRV and the amount of dirt on the fan, I figured maybe I could improve on this too. The bearings were good and not the source of vibration. Turned out to be mostly the dirt throwing the fan off balance. I may have to rethink the prefilter idea which is so coarse you can pour salt right through it. It was mainly to keep cat hair and dust bunnies from getting sucked into the fan. I wanted the high particulate filter on the discharge side to help muffle the noise. If one puts too much impedance on the intake, the fan blades will cavitate and make more noise whereas a bit of backpressure on the outlet side quiets it some.
Oh, I also found that the glue had let go on the seam of the noise reduction coupler so it was bypassing a lot of the air back to the intake. I can't believe they would not have sewn it. Anyway... it is much quieter now and moves a lot more air at lower speeds so I'm happy. As for rethinking the prefilter, maybe I should look into an electrostatic filter instead. I don't think they would provide very much impedance to airflow. Just so long as they don't produce ozone as I cannot tolerate even the smallest amount of it.
With it off all night, it couldn't run the de-icing cycles so I had to blow some heat on it to melt the ice. Once the ice was gone, it would not make the same noise so figure ice buildup was the likely culprit. While I was at it, figured I may as well rip it apart, dry it out well, clean it, and inspect it. Found a lower seal compromised and the squirrel cage fans had a lot of dirt buildup. Replaced the seal, cleaned her all up and was impressed with how much quieter it was. Funny how noise sneaks up on you and you don't notice. Anyway, impressed with the results, I turned my attention to my stove's central heat blower.
It is a variable speed 650 CFM, 8 inch centrifugal in-line fan. I built a housing for it down in the crawlspace where it draws in cool air off the painted concrete floor through a prefilter. It then goes through a flexible noise reduction coupler into the housing which has a labyrinth muffler and a 16x25x1 Filtrete high particulate filter before going up through the floor into the bottom of the stove. Ja, I know... I'm anal about sound reduction.
After seeing the failed seal on the HRV and the amount of dirt on the fan, I figured maybe I could improve on this too. The bearings were good and not the source of vibration. Turned out to be mostly the dirt throwing the fan off balance. I may have to rethink the prefilter idea which is so coarse you can pour salt right through it. It was mainly to keep cat hair and dust bunnies from getting sucked into the fan. I wanted the high particulate filter on the discharge side to help muffle the noise. If one puts too much impedance on the intake, the fan blades will cavitate and make more noise whereas a bit of backpressure on the outlet side quiets it some.
Oh, I also found that the glue had let go on the seam of the noise reduction coupler so it was bypassing a lot of the air back to the intake. I can't believe they would not have sewn it. Anyway... it is much quieter now and moves a lot more air at lower speeds so I'm happy. As for rethinking the prefilter, maybe I should look into an electrostatic filter instead. I don't think they would provide very much impedance to airflow. Just so long as they don't produce ozone as I cannot tolerate even the smallest amount of it.
