I built a 4′ wide by 3′ tall box for a 3 ton unit to sit on with the return grill with filter on the only usable wall of the box to retrieve air from the room.
Box is plywood, screwed and caulked.
We already replaced the swirl cage fan.
The grill is 22″ x17″.My A/C guy wants to put in a bigger grill but I am going to run into problems doing that; pipes room etc.
Is there anything I can line the inside of the box to reduce the noise that won’t disentigrate and end up being sucked into the unit?
ANDYSZ2
WHY DO I HAVE TO EXPLAIN TO FRIENDS AND FAMILY THAT BEING A SOLE PROPRIETOR IS A REAL JOB?
REMODELER/PUNCHOUT SPECIALIST
Replies
Is the noise vibration from the fan, or air turbulence? If air turbulence, is it turbulence IN the fan, or turbulence at the grille?
You can try taping an air filter over the return grille, to see if that helps. Probably one of the foam filters would be most likely to help. But depending on the situation the filter might just make matters worse.
Also, not clear is where the air is flowing. Is it being drawn into the box and then up into the air handler? If so, lining the box with standard duct lining material would probably help a lot, or you might be able to fit a commercial airflow silencer into the box. A bare-walled plywood box is just about the worst thing you could have for transmitting noise.
most likely in the grill...
use a pair of seamers to change the angle of the grill's vanes..
install a larger grill...
reset the the fan's speed down one notch...
check the fan's pillow blocks while yur in there...
if it has bushings instead of bearings... ditch the bushings and go with bearings...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
It is as loud with the grill on or off.
We tried a pleated filter and that didn't help much also tried a slower speed not much help either.
Next we are going to sealup the underside and then run a duct from the side of the unit back into the box and maybe by putting this little bit of distance and isolation from the fan it will reduce the noise.
Also contacting the factory to see what size motor came with unit as we only need a 1/3 hp and it could be a larger one as they spec 3 different sizes in the manual.
Our last resort is making a larger grill opening but I hate to make a mess of the finished product unless I have too.
ANDYSZ2
WHY DO I HAVE TO EXPLAIN TO FRIENDS AND FAMILY THAT BEING A SOLE PROPRIETOR IS A REAL JOB?
REMODELER/PUNCHOUT SPECIALIST
I had luck on the return grill right next to the computer by cutting a bunch of 100 psi (thin wall) 3/4" pvc tubing to 11 inch lengths and bundling them in parallel into the duct behind the grill - at least 6 dB noise reduction in my case. The particular return grill is only 3 feet from the squirrel cage fan. According to theory, drilling ofset 1/4" dia holes in the side of the tubing increases noise reduction even further, but was to lazy to do that at the time - prety labor intensive for a bunch of tubes.
JH,Would you know where I could get more info on your approach??I think I follow what you did, and I think I can see how it could work, and I would like to see if I can put something together w my own "junk".Thanks, Harry
up size the return....
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
We ended up sealing the bottom of the unit cutting a new whole into the side of the unit and attaching a 12" elbow.
That helped a good bit, but we then added a plywood partition and stack of solid concrete blocks to create a lenghthened chase with 2 more 90 degree turns. This really did the trick and everybody is happy.
ANDYSZ2WHY DO I HAVE TO EXPLAIN TO FRIENDS AND FAMILY THAT BEING A SOLE PROPRIETOR IS A REAL JOB?
REMODELER/PUNCHOUT SPECIALIST
excellent...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"