central air noise and vibrations
This is newly finished construction…
Imagine a rectangle and a small square in the middle ( the closet where the blower is for the A/C ). It’s truly central heat/air.
First problem, in the closet containing the blower, they installed the blower first, then the sheet rock second, so they were not able to fully cover the entire closet around the blower…on the inside, outside of the closet is fine. Oh, and did I mention there is zero insulation in the walls around the blower.
The blower is mounted in such a way that it radiates vibrations away from the little square in the middle of the rectangle throughout the house…well, in a 20-25 foot radius from the closet. And there is a hum or whirring of sorts that will drive you nuts if you stand in the right spot.
I’ve given up on the builder. He’s tried to help by calling subs ( like the A/C sub ) and they just come out and say you need to insulate this closet and all your problems will be solved. I seriously doubt it, but it will probably help some.
What needs to happen, in my opinion, is that the blower be removed and then the walls and floor properly insulated, then sheet rocked, then mount the blower properly.
Any good suggestions on how to isolate these vibrations and hums? I plan on ripping the sheet rock out and insulating the walls best I can myself. Any types of materials that might work better than others? I think the blower mounting in the closet needs to somehow be isolated from the rest of the structure of the house…not sure how to do this now, but that makes sense to me.
Replies
My blower had a nasty vibration that I was able to stifle with a wad of closed cell foam pushed between it and floor; your mileage may vary. If this is really bothersome I'd be tempted to do as you say; pull it out, insulate, Z-strips, DW.
Scott.
Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
I don't think you'll get much reduction from the insulation. You need mass (or isolation) to stop the vibrations being transmitted. You might be better off putting a 2nd layer of rock on the air handler unit room as opposed to trying to insul the walls.
The other post about foam between the AHU and the floor seems good.
What about the door tot he AHU room?
As always, great response from Breaktime.I plan to pull the rock off anyway, so when I put it back, I'll double it up as you said. I may also purchase an insulated door for the room as well. Insulated walls, two layers of rock and new door. That's a good start.It's really bizarre. This morning, getting ready for work, I'm sitting down in my bedroom tying my shoes and I can FEEL the vibrations through the floor. I need to keep the vibrations in or close to the closet or get them to be "soaked up" before the vibrations leave that room.
Be sure to take in consideration the new wall thickness when buying that door. May not end up being standard off the shelf and require a jamb extension. Usually not a big $$$ deal for that though.
Dunno square root of zero about hvac but I saw a Mike Holmes show (in Canada) where they replaced short lengths of metal duct (the main rectangular output and return)with a segment that had a heavy fabric segment. This was to reduce vibration & associated noise. Claimed that it worked but I have no way of knowing for sure.
The fabric makes sense. It's all about sound transmission. Those nice, rigid, straight pieces of sheet metal touching those nice, straight, rigid pieces of lumber...perfect for sound to move down.
Pieces of drywall in between the studs with a bit of insulation (to keep the panels from touching wood or drywall) will stop a lot more noise than insulation alone.
Open up the blower and make sure there is not a scrap of paper that would cause the fan to be unbalanced. Hand spin the fan and see if it rotates from being unbalanced.
A return air grill directly under the furnace is always noisy. If you have a raised foundation, block off the grill and run a large duct to pick up the return air from some other part of the house.
Not an unusual problem if you in fact have the blower unit sitting directly on the floor. Even the most balanced blower (assuming you have a squirrel cage type) is going to transmit vibrations through the surface its mounted on. And since you've got a unit in the middle of your floor area it is literally turning your entire floor into a drum head. And if your floor is sitting on long span joists even more vibration is possible.
Most furnace/blower units are in a basement, thus on concrete, or at perimeter of a home, where the load bearing is strongest and vibration is least.
On big commercial roof top mounted HVAC systems it is a requirement that they be mounted on "isolation dampers". Fancy name for little bity shock absorbers. For smaller units we sit them on curbs that have a rubber perimeter.
OK. This is really wierd. Had to stop for a cell call. It my HVAC sub. Seems he called me by mistake. Explained the problem. He agrees that the unit is probably fastened hard to the structure. Your local HVAC supplier has the solution. You ask for a rubber-faced cork isolator. Its about 1" to 2" high and you reset the unit on this. And as suggested by others you separate the ductwork from the unit by a flex connection (commonly called a "pair of pants", I didn't make that up!). If that doesn't do it there ain't much else.
As far as sound, use unfaced insulation in between the studs of the walls and, if you can, in the ceiling and floor. Sound, especially a low level hum or hiss, is a little monster to control but the above has been very effective in projects I've been involved in.
Man, that phone call was somethin'.
Hope I helped.
ciao. ted
Yes, that is amazing you got that call, I'll give thanks for Providence any day for such things.Ok, looks like I'm getting closer and closer to better-ing the situation using the suggestions given here.I don't really have hopes of fixing it all together, but if all these little things add up, I am hopeful that it will make a big improvement.