Inline Fans noisy & vibration….?
Good Morning,
I heat my house primarily with a wood stove and I recent cut in a vent in the ceiling over my stove and then ran insulated flex 6″ ducting over to the two kids bedrooms. I cut in vent in both those ceilings. Within each one of these runs I installed an 8″ inline fan. I created an L bracket out of scrap 2″x10″ and screwed the fan to the bracket and then the bracket to the ceiling joist in the attic. I had done this same project in another house I owned and it ran fine and was quiet. However, this time I am getting not so much noise but a vibration. The only difference this time around is I went with the 8″ fans and used reducers on either side to connect to the 6″ insulated flex ducting. All of these rooms are very wide open so I don’t think this is any kind of a back pressure issue but what I think I need to do is find some sort of foam rubber or cushion that I can put in between the L bracket that the fans are mounted to and the ceiling joist in the attic.
Any ideas on the kind of foam rubber I should use and/or where I can get this ???
Joe
Replies
Joe isolation would be good but a balanced fan would be better. I think return the fan for replacement, maybe it got dropped. It should run smoothly.
Rich
Hi,Let me clarify. I have two separate of the same kind of fans. Both are demonstrating the same noise/vibration qualities. I went into the attic while they were running and I laid my hands on the fans to see if perhaps I had not mounted them securely to the L brackets I created for them but there was no signifcant change in the noise/vibration. I still think it's how they're fastened to the ceiling joist. I used 4 3" drywall screws through the 2"x10" L bracket I made which is approx. 18" long.
I was even thinking of just trying a couple pieces of backer board in between the bracket and ceiling joist.....??
Joe maybe try just mounting the fan to the wood and then just laying the wood across the joists with some isolation material between the wood and the joists.The interlocking foam flooring sold in the BB stores should be about the right density.
This way the fan is totally isolated from the structure.
Piffin said he installed a fantech fan for a customer. They didn't think it was on and working. He had to take a dollar bill and let the suction hold the bill against the grate to show its working
try another brand
You want to use something stiffer that foam rubber -- something like neoprene that can damp the vibrations. Go to a real HVAC supply house (not HD or Lowes) and ask them about vibration dampeners or isolators. They have all sorts of rubber pads, hangers, etc. that you can choose from. You may have to experiment with a few to get something that works right for you.
Billy
P.S. I had to do this with a Fantech fan that was very quiet, but somehow set up a resonance with the gable studs where it was fastened in the attic, so you could hear a vibration in the bedroom wall below it. It was whisper-quiet in the bathroom where the vent was located, though.
Could your problem also be using 6 inch reducers on either side of the fan? Why didn't you just use a 6" fan?
Edited 2/9/2008 9:42 am ET by Billy
and then the bracket to the ceiling joist in the attic.
How about suspend it from a rafter? That's what we do with air handlers or fans in the attic and it helps a great deal.
Beer was created so carpenters wouldn't rule the world.
Don,Probably an excellent idea but I don't have enough extra flex ducting. I bought two boxes of 25' and what I cut off from one box to do the short run was just long enough to finish the long run to the far bedroom with the second box.
What I did end up doing with buying a foam exercise mat from Target. The foam is about 3/4" thick and I when I cut the mat in half I had enough to double up a section to go under each fan unit L bracket. I removed the screws that fastened the brackets to the ceiling joist as well.It's odd though because the unit that had the longest run of ducting and was the loudest is significantly quieter. The shorter run to the baby's room which was initially the least noisy is quieter but not as quiet as the room with the long run.....go figure....I'm done for now....they're working, they're quiet enough for the occupants to fall asleep to. I can revisit it later in my "spare" time. Thanks !J.
Probably an excellent idea but I don't have enough extra flex ducting.
Hanging it from the roof framing doesn't require any additional duct. None, zip. You don't even have to move the unit. Just support it a fraction of an inch from the ceiling framing and you've isolated the vibrations.
Beer was created so carpenters wouldn't rule the world.
I've installed several of those inline fans/duct boosters over the years. The Fantechs are pretty quiet and the rest are pretty noisey.
http://grantlogan.net/
Today we's learnin' about rawks. They's all kinds of rawks. These [picks up rock] is rawks which you throw. These here [throws rock at Rusty] is rawks that you get hit with. E.Cuyler
I mount mine on a sandwich of plywood and foam board. Quiet as can be.
You can see the top ply part in this pic. 1-1/2" rigid foam board under it, and another piece of ply below that to span the joists.
Mike Hennessy
Pittsburgh, PA
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